RV Weight & Safety Part 3: 5 Essential Lessons in Buying the Right RV Tires

Three years into our full time RV living, working and traveling adventures, I find myself more and more involved in the technical and mechanical aspects of our life on the road… like buying RV tires for Charlie-The-Unicorn RV.

As much as I love her, I like buying “new shoes” for our 2016 Entegra Aspire motorhome as much as I always have when buying tires for our cars – although I would prefer buying new shoes for Sherri!

Nevertheless, after talking about RV weight, both on the CAT Scales and four corner weighing, it’s time to circle back and talk about RV tires and safety. 

As with most things in life, you don’t know what you don’t know until you figure it out, whether the easy way or the hard way. It feels like we’ve learned about buying and replacing RV tires the hard way over the last three years, so I’m here to share our experience and help other new and/or less technical RV owners, especially if you own or intend to buy a “new to you” (pre-owned) RV.

Here are 5 essential lessons to buying RV tires the right way:

  1. Know your weights and limits
  2. Verify your RV tire size
  3. Locate your date codes
  4. Check your load range
  5. Determine your optimal tire pressures
RV Federal Compliance Label

Lesson 1: Know your weights and limits

First things first: Find your “stickers” (Federal Compliance Labels). In a motorhome, these are generally located near the driver’s door or on the wall near the driver’s seat. 

The most important information on this label, with respect to your tires, are the GVWR and GAWR:

  • GVWR (Gross Vehicle Weight Rating) – the maximum weight limit of the vehicle and everything in it, including passengers, pets, gear, provisions, furniture, accessories, fluids (fuel, propane, water, etc.) and all of your household and personal goods.
  • GAWR (Gross Axle Weight Rating) – the maximum weight limit on each axle. It is possible to be under the GVWR and still exceed an axle rating, depending on how your RV is loaded (i.e., the weight distribution on each axle).

You’ll also find your recommended tire sizes (front and rear) next to the Gross Axle Weight Ratings.

Charlie-The-Unicorn RV

Charlie-The-Unicorn RV’s Tire History

In September 2020, we bought our new-to-us 2016 Entegra Aspire online from a dealer in Florida (Sadly, it was not NIRVC, as this was before we knew about NIRVC). It all worked out, for the most part, with an abundance of research, several video walk-throughs, a thorough independent inspection, and two complete PDI’s (pre-delivery inspections), both virtual and in-person. We knew where to look for our weights and limits.

The dealer transported the coach from Orlando, Florida to Des Moines, Iowa, where we picked her up for our first big road trip, back home to Seattle, Washington. She had less than 5,000 miles on fairly new Michelin tires. The tires all looked and performed great for the 1,800-mile adventure, which you can read about in my blog, RV Road Trip: How We Survived Our First Epic 21 Day Adventure.

RV tire

Lesson 2: Verify Your RV Tire Type & Sizes

As I mentioned in Lesson 1, it’s easy to locate your recommended tire sizes on your Federal Compliance Label. The next step is to verify those tire sizes on your motorhome by looking on the sidewalls of your tires. The numbers should match. In the example above, the tire size is: 295/80 R 22.5.

When it comes to determining accurate tire pressures, you’ll also need to know the manufacturer and type of tire you have. In the example above, it’s Michelin XZA2.

In fact, all of your important tire information can be found on the sidewall of your tires, including the tire size, date code, and load range.

This information may not be super critical when you’re taking delivery of a brand-new motorhome at a dealership, but you will eventually need to know it for weighing your RV, tire pressure management, and if/when you need to replace any of your tires.

If you are buying a pre-owned RV, whether from a dealer or a private party, I highly recommend verifying the tire sizes, dates codes, and load range on the sidewalls of all the tires. 

Charlie-The-Unicorn RV

In May 2021, we replaced the front tires before we set out to travel full time across the country. We worked with a trusted tire shop that was part of a well-known franchise in Washington (and all over the West Coast). My husband handled that – before I was fully onboard with the whole idea of full time RVing, quite honestly.

The RV had been sitting for a couple of months or more on concrete at the dealership in the Florida sun and heat. He felt safer driving the RV long distance with brand-new drive tires on the front, but decided we could wait a year to replace the rear tires. 

In July 2021, we set off across the country, from Washington State toward our first winter in Florida.

DOT Code

Lesson 3: Locate Your Date Codes

Your date codes can be located on the sidewalls of your tires. It will be a 4-digit number enclosed in a stamped oval at the end of the DOT Code (a longer series of numbers and letters that begins with DOT, as required by the Department of Transportation on all tires).

The date code on the tire above is 3 5 2 1, from our first set of rear replacement tires.

  • The first two numbers indicate the week of the year manufactured (35).
  • The last two numbers indicate the year of manufacture (2021).

So, these tires were manufactured the 35th week of 2021, which was August 30 to Sept 5, 2021. They were installed October 2021, so those were some fresh tires!

Here’s one of the first things you learn about RV tires: RV tires age out before they wear out…

…even if they look brand-new, with barely worn tread.
…even if they have incredibly low mileage on them.
…even if the RV has been in storage for months or years.
especially if the RV has been parked outdoors in the sun.

RV tires, whether they have been driven on the road or not, age out between 5 to 7 years from the date they were manufactured (Date Code).

RV pulled over

Lesson Learned

In September 2021, we were caravaning with friends, following behind them towing their 2015 Sanibel 5th Wheel on Interstate 10 WB in Florida, heading toward a fun weekend in New Orleans. While we were on the busy side of I-10, one of their rear tires exploded at full speed, ripping away much of the rear panel of their RV. Thankfully, they were able to make it over to the shoulder, and we stopped with them. It was a scary experience!

Their RV Roadside Assistance never showed up. Fortunately, Road Ranger Service Patrol, the Florida Department of Transportation’s emergency roadside assistance service, responded very quickly and helped them with their spare tire so they could move their coach to the nearest rest area.

We found a reputable local mobile truck tire service that came to the rest area and replaced all five tires on the 5th Wheel, including the spare. We all got back on the road later that evening. Instead of continuing on all the way to New Orleans, we decided to stop and enjoy our long weekend together on a beach in Pensacola, Florida.

In October 2021, after that experience, we returned to our RV property in Central Florida and immediately replaced all four rear tires on our motorhome. I was much more involved this time, doing the research and making the arrangements while my husband was working.

RV Tires & Full Time Challenges

I tried to buy tires through the FMCA Tire Buying Discount Service, but it was way too complicated. I had to call local heavy truck tire and service places in the network to find the correct tires and then arrange a time to take the RV to their shop for installation. This is a huge challenge of living full-time in an RV, especially working from home, with Hubs on video conferences all day. It is no easy task to bring your RV in for service.

load range

Lesson 4: Check Your Load Range

This is the most elusive, secret little letter you can possibly hope to find on your tire sidewall. But it’s there. And it’s super important.

Load range is a measurement of the inner strength (number of plies/inner layers) and load capacity (maximum weight and PSI) of your RV tires. For larger Class A motorhomes, it is indicated on the sidewall by a single alphabetic letter – typically G (14 ply) or H (16 ply). The higher the letter, or the number of internal plies, the stronger the tire.

RV tire

The Secret Letter

In October 2021, we ended up buying four new rear tires from MotorhomeTires.com, an AIM Club Sponsor (Again, this was before we knew anything about NIRVC or the AIM Club). They were very easy to work with. MotorhomeTires.com offers great educational information on their website. We worked with their service advisors to check our tire sizes and date codes.

MotorhomeTires.com sent a local contractor to us for tire installation, which was easy and convenient. In the end, we ordered and paid for Load Range H (16 ply) tires on the invoice, but the installer, in error, installed Load Range G (14 ply). We knew to verify the tire sizes and date codes, but we didn’t know anything about load range… until we got the rig four corner weighed at the FMCA Rally in Perry, Georgia.

When we subsequently discovered the load range error, almost 18 months later, MotorhomeTires.com arranged an immediate replacement of all four LRG tires with new LRH tires at no charge!

I would still recommend MotorhomeTires.com for their great service, convenience, responsiveness, and RV tire education.

As the RV owner, you need to know what’s important in ordering and checking your new tires before installation:

  • RV tire size
  • Date code
  • Load range

Lesson 5: Determine Your Optimal Tire Pressures

Load and Inflation Tables

Once you have your weights and tire information, it’s time to go to your tire manufacturer’s Load and Inflation Tables online to determine your optimal tire pressures (PSI) for safe driving.

The example above is the table for our front tires (Michelin XZE 295/80R22.5 H)

  1. Have your four corner weights handy.
  2. Find your Load and Inflation Tables online by searching: [Brand] RV inflation tables for your tire manufacturer.
  3. Read down the left column of the chart to Single or Dual Axle rows in LBS. For front tires (single), locate the column with the weight of your heaviest tire on the axle. Scan up from there to locate recommended PSI. For Rear Tires (dual), locate the column with the weight of your heaviest wheel position (driver or passenger side). Scan up from there to locate recommended PSI.

Note: Never exceed the wheel/rim manufacturer’s maximum air pressure limitation.

That’s it for this three-part series on RV weight and tires! I hope this information and our learning experiences will help you on your way to safe and happy travels in your RV!

National Indoor RV Centers blogger Sherri Caldwell profile image

Sherri Caldwell is the founder of BooksAndTravelUSA.com, a full-time RV travel blog and book club/U.S. literacy project. Sherri and her husband Russ are currently living, working and traveling full-time in their 2016 Entegra Aspire 40P, Charlie-The-Unicorn RV.

Tune in to NIRVC on RVTV

Take a break from your next road trip and tune into NIRVC’s three new series featured on RVTV! Hosted by Angie Morell, NIRVC Director of Sales, these shows will provide entertaining and informative content for both beginners and full-time, seasoned RVers alike.


NIRVC’s Three New Series:

The NIRVC Show
At NIRVC, our mission is to make RV ownership simplified. The NIRVC Show features educational sessions on a variety of RV topics, including tips to enhance your RV lifestyle, how to protect your investment, and more!

Watch some of the most popular RV tours in the industry! In our series RV360, Angie will take you through the latest luxury RV models – highlighting floorplans, appliances, exclusive features and everything in between.

Want to hear the latest industry news from those who know it the best? Don’t miss an episode of RV U, where host Angie Morell chats with forward-thinking RV industry experts, icons and influencers. Hear the latest from brands like Newmar, Entegra, Fleetwood RV and more!

We’re also proud to announce that we are the exclusive Class A sponsor of RVTV.

Tune in and view the weekly schedule.

Check your local cable listings to see where you can watch RVTV in your area. RVTV is also available on Roku and Amazon Fire TV.


RV Weight & Safety Part 2: RV Tire Four Corner Weighing

How Much Does Your RV Weigh?

In Part 1 of this three-part series, we talked about quickly and easily weighing your RV on the CAT Scales. There is, however, a limitation to consider, when you only know your overall weight, or even your weights per axle.

Remember, the primary concern for weighing your RV, and adjusting tire pressures accordingly, is to avoid overloading any of your individual tires. Unless you know the load/weight carried by each wheel position, you have no way to know the proper inflation of your tires. Improper inflation leads to improper wear, reduced life of the tire, and greater potential for rapid tire failure. Learn more.

RV Four Corner Weighing

So, after your preliminary weigh-in on the CAT Scales, this then becomes the Holy Grail or Level-Up Quest for the new RV owner: four corner weighing, also known as wheel position weighing.

The four corner weight is the distribution of weight on each of the four wheel positions of your RV.

We finally had our chance to weigh-in properly – all four corners, or wheel positions, of the RV – with RVSEF (RV Safety & Education Foundation) at the FMCA International Convention & RV Expo in Perry, Georgia.

RVSEF maintains a full schedule of attendance at RV rallies and manufacturer brand events all over the country. They teach tire and weight safety seminars and provide wheel position weighing at events.

When you register for an FMCA Rally, or any of the events RVSEF is attending, you’ll typically receive early notice via email about signing up for wheel position weighing. You can schedule your weigh-in before or after the event, on your way in, or when you leave. Very convenient!

RV Goals: Four Corner Weigh

We had been on the road full time for two years before we had the opportunity to finally sign up for our four corner weighing. We were fairly confident we were on top of tire safety and RV weight:

  • We replaced all six tires on Charlie-The-Unicorn RV in our first year. 
  • We rolled onto the CAT Scales several times in our travels to verify overall weight, axle weight and tire pressures. 
  • We researched, purchased and installed our TireMinder tire pressure monitoring system.
  • My husband checked the tire pressures regularly, as part of his travel day checklist. 

We rearranged our travel schedule to do the four corner weigh on our way into the FMCA Rally. I scheduled the appointment just before our assigned parking time with the AIM Club.

The wheel position weigh station is a portable setup, with big rolling scale plates the RVSEF techs position under the tires, and a computer with a printer to generate the reports in real time. This all requires a flat roadway for accurate weighing, as well as plenty of room to maneuver the large RVs coming and going. 

RVSEF typically arranges the weigh-ins at a suitable location near the actual event. In Georgia, it was at a small airport near the Georgia National Fairgrounds & Agricenter.

four corner weighing station
RVSEF weigh station setup (courtesy of Trey Selman/RVSEF)

How Do I Get My RV Weighed?

Along with the appointment date, time and location specifics, you’ll receive additional information and homework ahead of time. Be prepared!

RV tire

RV weight information needed from your RV tire sidewalls:

motorhome information card

The homework is necessary information and helpful education for the RV owner. This was the first time I really looked at the Federal Compliance Labels in our rig and got to know our motorhome tires up close and personal.

In Charlie-The-Unicorn RV, my husband tends to do most of the driving. He handles the technical and mechanical aspects of our life on the road, while I navigate and manage the logistics of travel and household management. He also works full time and is on video conferences with partners and clients all over the world all day, every weekday. I have more flexibility with my work, so I help with the details, such as filling out the homework sheet for our Wheel Position Weighing.

I got organized, did the detective work, and learned all about the RV weights from the compliance labels and information on the tires. I looked up all the terms and definitions as I went.

Little did I realize how important load range would be. (More on that later…)

Four Corner Weigh: Preparation 

 When weighing day finally rolls around, there is even more prep to be done. You’ll want to go into your RV weigh-in as heavy as you can be, to truly test your limits, even if you don’t normally travel fully loaded.

liquid weights chart

We drove our RV onto the scales with a full tank of fresh water (830 lbs!), plus full diesel and propane tanks. Our black and gray tanks were empty.

Keep in mind that the total weight of your RV includes people – and pets!

Four Corner Weight Results

After all the scheduling, homework and prep, the wheel position weighing was an easy process. We arrived at the airport and only had to wait less than five minutes for the RV ahead of us to finish. After paying, I climbed aboard and took my usual seat. Hubs rolled Charlie the Unicorn’s tires up onto the four weight scales. The RVSEF team recorded the weights and brought the results over to discuss the GVWR, GAWR and GCWR.

  • GVWR (Gross Vehicle Weight Rating) – the maximum weight limit of the vehicle and everything in it, including passengers, pets, gear, provisions, furniture, accessories, fluids (fuel, propane, water, etc.) and all of your household and personal goods.
  • GAWR (Gross Axle Weight Rating) – the maximum weight limit on each axle. It is possible to be under the GVWR and still exceed an axle rating, depending on how your RV is loaded (i.e., the weight distribution on each axle).
  • GCWR (Gross Combination Weight Rating) – the maximum combined weight limit of your motorhome and the attached tow vehicle, including all passengers, cargo and liquids in each vehicle.

Four Corner Weight Report

four corner weight report

Basically, WE FAILED!

We were HEAVY on the Passenger Front (my side!) by 200 lbs, according to the Axle Rating: GAWR (Front) 14700 / 2 = 7200 lbs max per tire.

But also, and in my mind, far, far worse: 1,100 lbs MORE than Driver Front. What?! I’ve actually LOST all 15 lbs of my gained RV weight. I was devastated!

Overall, we were well within our GVWR and GAWR (front and rear) – as our CAT Scale weights had shown – but the distribution of the weight between the four wheel positions was out of whack, which affects the individual wheel position tire pressure requirements for safety.

How Can Your RV Be Overweight and/or Unbalanced?

RVSEF’s suggestions for the weight variance in our RV, included several possible factors:

  • Storage in the bin below the passenger seat? My storage included an Instant Pot, camp decor (lights/tablecover, etc.) and a rope hammock: 1,100 lbs?! I think not. However, the house batteries are also up in the front. (That must be it? No.)
  • Generator in front offset? (No, the generator is centered in front.)
  • Diagonal weight variance on corners due to air suspension system?
  • Rest assured, it wasn’t me! And it didn’t indicate a broken frame (another unreasonable fear I had).
  • Our motorhome was safe to drive, but we needed to get it checked out as soon as possible.

Their recommendation was to run the tires at the highest PSI allowance (pounds per square inch), front and rear: 120 PSI. We didn’t immediately do that, because we were going directly into the FMCA Rally, which was just a few minutes away, and parking for the rest of the week. 

It’s actually a really good thing we did not increase the tire pressures at that time…

In retrospect, we’re happy we scheduled the four corner weigh-in on our way in, before we attended the FMCA Rally, so we had a chance to do more research and ask questions.

RV Unbalanced: Ride Height?

None of this made any sense to me. I had to go deeper. Research. Ask questions.

The first person I talked with was Ted Cook from Entegra Coach, AKA Entegra Ted. Ted’s business card says Regional Sales Manager, but he is much more than that, having been with Entegra Coach before they were even building motorhomes.

Ted Cook
Entegra Regional Sales Manager Ted Cook (Entegra Ted)

Jayco/Entegra Coach purchased the assets of RV manufacturer Travel Supreme in 2008. Ted came to Entegra through that acquisition. He was VP of Operations at Travel Supreme and had worked for the company since 1990.

I discovered this mention of Ted in the September 2006 issue of FMCA’s Family RVing Magazine:

No Shortcuts Allowed at Travel Supreme

…Mr. Cook, a 16-year company veteran, has played a significant role in the design and mechanics of Travel Supreme motorhomes. For instance, he was determined to build a slideout mechanism that would be flush with the floor, all the while keeping the baggage doors full-size. Thanks to some clever engineering, this was accomplished.

Entegra Ted knows pretty much everything there is to know about Entegra Coaches – and high-end motorhomes in general. As Entegra Coach’s Regional Sales Manager, he works closely with NIRVC to represent Entegra and to support dealership sales and service. He’s also a great guy, fellow AIM Club Member, and part of the NIRVC family, so we all have the pleasure of seeing him at RV events, shows and rallies.

Ted looked over our Wheel Position Weight Report and suggested we take a look at the ride height, which is the setting for the air suspension on your chassis. Ride height is very, very important.

Edward from Freightliner, Entegra Ted, Sherri Caldwell
L to R: Edward from Freightliner, Entegra Ted, Sherri Caldwell

I learned a lot about our air suspension system and ride height from Entegra Ted and our friends at Freightliner, an AIM Club founding sponsor. There was indeed a small ride height adjustment made by the end of our unbalanced adventure.

Ride height can affect the diagonal weight variance on opposite corners due to air suspension. That is something that should be checked by your chassis manufacturer or a qualified service technician, especially if you have a problem with your four corner weights.

But there was something else going on here…

RV Weight & Tire Safety Seminar

Two days later, during the FMCA Rally, I attended the RVSEF Seminar: RV Weight & Tire Safety presented by Trey Selman, Executive Director of RVSEF. It was a fascinating and comprehensive presentation, and I encourage any RV owner to attend if you have the chance.

After the seminar, I had a chance to personally ask Trey some questions about our weight problems. He reviewed our Wheel Position Weight Report and the recommendations, as well as the tire info I had recorded on the Homework Sheet.

And there it was, right on the Homework Sheet:

homework sheet

G load range and the WRONG tires!

Ultimately, we discovered that we had the wrong load range rear tires on our motorhome… for the last year and a half.

With the rear tires we had (Load range = G), the MAX pressure was 110 PSI, and the MAX weight was 5,675 lbs per tire, which was insufficient for our motorhome based on our GAWR and the weight distribution on the rear axle. Our tires all should have been Load range = H. (Wrong tires?! How did this happen?!)

But first, let’s talk about the end of the story…

RV Weight: Four Corner Weighing For Safety

When the pieces of the puzzle finally fell into place, we were able to make the arrangements and get our particular RV weight problems corrected: 

  1. Replaced all four rear tires with proper load range tires
  2. Adjusted ride height
  3. Redistributed weight in the basement storage bins
  4. Retested our four corner weights

Final results: WE PASSED!

The cost of Wheel Position Weighing with RVSEF at the FMCA Rally was $70.

It was well worth the money for the convenience of the timing and location, the overall education in RV weight and safety, the one-on-one personal assistance when we had weight problems, and our resulting confidence in the weight, distribution and safety of our motorhome on the road.

Something we learned along the way: The cost of four corner weighing with NIRVC at any of their six locations across the country = FREE. (We were RV owners for nearly three years before we learned this!) It’s important for RV owners to know their Four Corner Weights for weight distribution, proper tire pressures, and confidence in their equipment and safety.

We were able to retest our four corner weights after all the adjustments and corrections at NIRVC Las Vegas.

“We do currently have the capability of four corner weighs at all locations. This is a FREE service we offer,” explains Eddie Braley, General Manager of NIRVC Dallas. “We do request that you call ahead to schedule, as there is some setup time required. The service is offered to all RVers regardless where they bought their RV.”

National Indoor RV Centers blogger Sherri Caldwell profile image

Sherri Caldwell is the founder of BooksAndTravelUSA.com, a full-time RV travel blog and book club/U.S. literacy project. Sherri and her husband Russ are currently living, working and traveling full-time in their 2016 Entegra Aspire 40P, Charlie-The-Unicorn RV.

An Investment Worth Protecting: The Importance of RV Storage

When giving your RV a break from road trips and weekend getaways, storing it in a safe, secure facility is essential. Not only does storing your RV indoors protect it from the elements, but it also helps safeguard its overall value. NIRVC offers plenty of convenient storage options at our Atlanta, Dallas, Las Vegas, Phoenix, and Nashville locations.

Storing your vehicle — whether a class A, B, or C motorhome, towable, or boat — should be easy, convenient and safe. NIRVC offers concierge indoor storage and service at five of our locations:

Atlanta – (770) 979-4051

Dallas* – (469) 277-1330

Las Vegas – (702) 766-7770

Phoenix – (520) 442-2500

Nashville – (615) 527-8960

*At this time, our Dallas location is not storing boats or towables, only motorhomes.

Our Phoenix and Nashville locations are currently running a promotion for new customers! Store your RV, boat and/or towable for just $10/ft per month. Call or visit nirvc.com/storage for more information.

The Benefits of Our Storage Facilities

In addition to the convenience of not maintaining your RV in the off-season, a good storage facility also provides you with the peace of mind that your RV is safe and being properly tended to. Here are a few key reasons to consider storing your vehicle with NIRVC.

  • Weather Protection: Our indoor storage facilities keep your RV safe from the elements. From bumper-to-bumper your RV is protected from the summer sun and the winter snow.
  • Convenience: NIRVC offers on-site repair services, dump stations, a detailing center, and free valet parking. 
  • Security: Your coach is a prized possession and deserves to be protected in every way. Our security system is state of the art.
  • Cost of Ownership: By storing your RV indoors, it will have retained more value when you’re ready to sell.

We’re Here to Serve You

While your vehicle is stored, we can perform warranty service and routine maintenance. We work with all manufacturer warranties and extended service plans. Collision repairs, as well as Paint & Body upkeep, are performed onsite in our body shops. We work with all insurance companies to make things easy on you, and your wallet. And to preserve your coach’s beauty and functionality, we provide external and/or internal washing and detailing, upon request.

To learn more about our indoor storage facilities, contact us today!

RV Weight & Safety Part 1: How Much Does an RV Weigh?

So, how much do you weigh? Kinda personal, right? But it’s a thing in the RV world… Of course, I’m talking about your RV! (Mostly. 😉)

What’s the Big Deal about RV Weight?

In a Class A motorhome, you’re not just driving a ton of weight down the road. It’s actually more like a dozen tons of weight – or much more, depending on the size of your RV (and everything in it, including you).

In a word, the big deal is SAFETY.

Overloading or improper distribution of RV weight can:

  • Affect control of your motorhome while driving or braking.
  • Add stress and wear and tear to chassis components, leading to damage and potential failure.
  • Cause catastrophic tire damage, resulting in a serious accident.

While we’re talking about tire safety and blowouts, I have to mention RettroBand® Wheel Enhancement, which is exclusively distributed by National Indoor RV Centers. NIRVC offers a limited, highly selective line of RV aftermarket products for added safety, protection and convenience, including RettroBand, which was developed to protect your RV in the event of a tire blowout.

For more information and a video of RettroBand in action with NIRVC CEO and President Brett Davis, visit rettroband.com.

RV Weight & Tire Pressure

Knowing the weight of your RV helps you determine appropriate tire pressures for safe driving, based on the actual weight and the Load and Inflation Tables for your specific tire manufacturer and type of tire.

Load Inflation Tables, often referred to as LITs, are a tool used by manufacturers, tire retailers and automotive professionals to determine the appropriate inflation pressure for tires based on the load that they will be carrying. These tables provide a reference for adjusting tire pressure to ensure optimal safety, performance and longevity of the tires.

How Much Should an RV Weigh?

The first place to start is knowing the basic limits of your RV. For instance, how much weight was it designed and built to carry? This information can be found on the “stickers” – or Federal Compliance labels – in each and every RVIA-certified motorhome.

These are generally located near the driver’s door or on the wall near the driver’s seat. Locate these stickers in your RV and make note of the critical Weight Ratings for your vehicle (See below).

Federal Compliance label
The Federal Compliance label located on the wall behind the driver’s seat in our 2016 Entegra Aspire
Federal Compliance label
The Federal Compliance label located behind our driver’s seat on the screen door

What You’re Looking For & What It Means

  • GVWR (Gross Vehicle Weight Rating) – the maximum weight limit of the vehicle and everything in it, including passengers, pets, gear, provisions, furniture, accessories, fluids (fuel, propane, water, etc.) and all of your household and personal goods.
  • GAWR (Gross Axle Weight Rating) – the maximum weight limit on each axle. It is possible to be under the GVWR and still exceed an axle rating, depending on how your RV is loaded (i.e., the weight distribution on each axle).
  • GCWR (Gross Combination Weight Rating) – the maximum combined weight limit of your motorhome and the attached tow vehicle, including all passengers, cargo and liquids in each vehicle.

What are the Maximum Allowable RV Weight Limits?

By examining the applicable Weight Ratings on the two stickers, we determined the maximum allowable weight limits for our motorhome, which are summarized below. This is helpful information to have on hand (perhaps in a note in your smartphone) when you’re loading and weighing your RV.

GVWR, GAWR, GCWR weights of 2016 Entegra Aspire RV

How Do You Weigh an RV?

Once you know your weight limits, it’s time to take your fully loaded RV and tow vehicle to the scales! This can be easier said than done, but we’ll start where most of us do:

At the Truck Stop

The easiest and fastest preliminary weigh-in method is on the CAT Scales at your nearest truck stop. It can be fun driving up on the CAT Scales, like the big boys and girls in the semi-trucks… if you know what you’re doing!

If you’re new to this process, here’s a quick primer:

1. Download the CAT Scale Weigh My Truck mobile app. Once you set up your account, you can do it all on your phone: 

  • Find a CAT Scale location near you
  • Pay as you weigh (Current price: $13.00)
  • Weigh your motorhome and towable
  • Get your weight report immediately
  • View the record of your weigh-ins

The Weigh My Truck app displays your weights immediately on your phone. You can also view a PDF for comprehensive information about the CAT Scales Certification & Guarantee for professional truck drivers.

2. Watch this helpful YouTube video from Mortons on the Move: Weighing the RV the easy way with the Weigh My Truck App

It’s as easy as driving your RV across the scales! The only difference in a Class A Motorhome is that you must stop with your front and rear axles of the RV on the first and second plates, and with your tow vehicle positioned on the third plate.

RV being weighed on the CAT Scales
CAT Scale ticket with RV weights

RV Weigh Results: Did We Pass?

CAT Scale weights vs sticker max weights for RV

YAY! We were under the weight limits based on axle weights and GCWR, including our tow vehicle. But hold on a minute…

RV Weight Limitations of the CAT Scales

As helpful as the CAT Scale weights are for overall weight and load on each axle, including the tow vehicle, it doesn’t tell us anything about the weight distribution, side to side, on each wheel position, on the tires. This information is extremely important when it comes to safely and accurately managing tire pressures on all tires.

Note: Unless you know the load/weight carried by each wheel position, you have no way to know the proper inflation of your tires. Improper inflation leads to improper wear, reduced life of the tire, and greater potential for rapid tire failure. Learn more.

Beyond the CAT Scales

If you just can’t find a place to get your RV weighed wheel-position-by-wheel-position, weighing on a platform scale gives you the basic starting information. Then, you can get wheel-by-wheel weighing done when you have the opportunity.

National Indoor RV Centers blogger Sherri Caldwell profile image

Sherri Caldwell is the founder of BooksAndTravelUSA.com, a full-time RV travel blog and book club/U.S. literacy project. Sherri and her husband Russ are currently living, working and traveling full-time in their 2016 Entegra Aspire 40P, Charlie-The-Unicorn RV.

RV Sanitation Systems

Understanding your RV sanitation systems can prevent some foul problems

Motorhomes are self-contained with a fresh water system as well as holding tanks to handle waste water from the various plumbing fixtures. While dealing with waste water isn’t the most glamorous part of owning a motorhome, it is nonetheless an important part. Unlike a residential plumbing system like in your home, an RV has a number of things that have to be kept in mind and taken care of or else you’ll be in for a few messy and smelly problems. Fortunately, it’s not that bad if you understand how things work and pick up a few tips to help keep them working as it should. Let’s first look at how an RV’s waste water system is constructed.

Your RV Has Two Water Systems – Not One

To begin with, there are really two systems, not just one. The gray water system handles the waste water from the sink drains, shower drain and dishwasher, if equipped. The black water system handles the waste from the toilets. This method provides for two separate holding tanks, one to hold the black water and one to hold the gray. The reasoning behind this began in the early days of RV use. Drainage from sinks and showers contributed more volume than waste water from the toilets and needed to be drained more frequently. In addition, the gray water was relatively clean and could oftentimes be allowed to drain onto the ground, although many locations no longer allow that due to local public health laws. On the other hand, the black water wasn’t very sanitary and needed to be disposed of in a proper dump station or sewer connection. Having the two separate tanks made it possible to have multiple dump cycles rather than dumping all the waste at the same time. Another benefit to the two-tank system is that the gray water tank is relatively clean because it’s mostly soapy water while the human waste and toilet paper found in the black tank can cake up inside the tank walls, causing tank level sensors to foul and give errant readings.

The vast majority of motorhomes have a single sewer connection used to connect the sewer hose to the holding tanks. A pair of dump valves, one for each holding tank, connects via a wye connector to this common outlet. These valves are blade type valves to prevent clogging and can be either manually operated or electrically operated with a remote switch.


A set of remote electric dump valve switches in our Entegra Coach.

Each tank is connected to a vent stack that extends out of the roof to eliminate a vacuum from forming in the tank when draining and expansion as the tank is being used. It also allows for odors to vent from the tank. You may have a pair of vent stacks for the two holding tanks, or they may be tee’d together into one common vent stack. A hood is applied to the vent stack to prevent rainwater or debris from entering the tanks via the vent stack. These hoods can be simple rain caps or venturi style fittings that allow the wind to help ventilate the tanks.


Rooftop vents, such as this 360 Siphon, are required to ventilate the holding tanks and provide makeup air when draining the tanks.


Of course, you’d never know when you have to dump your holding tanks without some kind of indicator. Early tank designs used three sensor probes that were inserted into the tank. One was located at the one-third level, another at the two-thirds level and one at the very top of the tank. These sensors were inserted through the sidewall of the tank and would conduct electricity when wet. A wiring harness connected them to a monitor panel inside the coach to display the tank levels. If the tank was full, all four LEDs would illuminate. If the fluid level in the tank reached the two-thirds level, only three LEDs would light up. At one-third, only two would light up and if below one-third, only the bottom “empty” LED would be lit.

This system worked for years but had a few drawbacks. For one, the sensors easily fouled and gave false readings, so it was imperative to keep the tanks as clean as possible. Another concern was their accuracy. If the tank level was just below the two-thirds sensor, it would register one-third full on the display. You might think you have plenty of room left in the tank but all you had to do was add a little bit of water to the tank and it instantly jumped to two-thirds full, so you never really knew exactly how full the tank was.

The next big improvement was the SeeLevel tank measurement system. This system used external sensors that used adhesive to attach to the outside of the tank. These sensors were full length and used radio waves to determine the precise level of the tank’s contents.


The SeeLevel system uses digital sensors that are externally mounted to the tank and displays the levels in 2% increments on a digital display within the coach.

A second SeeLevel display panel can be mounted in the wet bay to monitor tank levels when draining or filling the tanks.

In addition, the external mount prevented the sensor from fouling. The only time an errant reading was displayed was if the inside tank wall was seriously caked up and needed a major cleaning. The display panel inside the coach was a digital display that reported in actual percentages, usually with 2-4% accuracy. The displays were available in multiple configurations that could cover the LP tank level if needed as well as switches for water pumps. Multiple displays meant you could have one display inside the coach with a second display in the wet bay. Eventually this sensor technology also found its way into the multiplex wiring systems, such as Firefly’s VegaTouch system, so that it could be displayed on their central touch screen panel.


Typical basement wet bay from my Allegro Bus, showing water filter, hose reel, dump valves, water pump and all valves and controls.

RV Toilets

While sinks, showers, dishwashers and laundry centers aren’t that much different than what you would find in a sticks and bricks home, the toilets used in an RV are markedly different. A residential toilet has a large water closet that acts as a storage tank for clean flush water. It also has a trap that fills with water to prevent any sewer gas from backing up into the home. When you press the flush lever the tank water runs into the bowel with a vengeance, rinsing the bowl and using gravity to flush the water down into the sewer. The tank then refills with water to be ready for the next flush. An RV needs to conserve water because both the freshwater and holding tanks are limited in size, so a different design is used. In most cases an RV toilet consists of a blade valve that is kept closed except when flushing. These gravity dump toilets are placed directly over the black water holding tank. The blade valve is either operated manually via a foot pedal or electrically via a wall mounted switch. When you activate the flush mechanism, the blade valve opens to allow the waste to fall into the tank below and a measured amount of flush water is expelled to rinses the bowl and provide some water to the holding tank to prevent the waste from drying out.


If the dump valve blades get sticky a drain valve lubricant can be added to the tank to help free it up.

In some cases, it’s not possible to locate the toilet directly over the black tank. This is especially true when your coach has a 1.5 bath floorplan with one toilet midship and another in the rear bath. In that case, a macerator toilet is used. A macerator toilet uses a motorized grinder to grind the waste up and pump it to the black tank regardless of where the tank is located. Instead of a blade valve, this style does use a small trap filled with water. When you push the flush button, the bowl fills with more water and then the macerator kicks in and pumps the waste through a smaller 1-1/4” line to the black holding tank. Then it adds some more water to the bowl. Macerators are necessary when the black tank isn’t located beneath the toilet. The only real disadvantage to them, other than cost, is that they do use more water when flushing than a direct gravity dump toilet, which can be a concern when boondocking with a limited water supply. However, the extra water used helps to keep the solids in the black tank suspended and will keep the tank walls cleaner.


Macerators use a smaller diameter 1-1/4 to 1-1/2” hose and can pump the waste uphill and for longer distances than a gravity dump 3” sewer connection.

RV Sewer Hoses and Fittings

You need to have a way to transfer the waste from the tanks to a sewer connection or dump station so that requires a sewer hose. Sewer hoses use a common 3” inside diameter hose with an industry standard bayonet connection. These “slinky” hoses are typically vinyl with a spiral wire reinforcement to prevent the hose from collapsing and come in various grades. The cheapest hoses are very thin and won’t last very long. You will develop pinhole leaks, cracks and tears quickly. Upgrading to a heavier vinyl helps but even with the extra heavy-duty hoses, you’ll still have issues. Many motorhome owners have gone with Camco’s Rhino Flex hoses, which are a step up over traditional vinyl hoses. These hoses can hold their shape more easily and are quite a bit stronger. My personal choice is Valterra’s Viper sewer hose. The Viper hose is unique in that it doesn’t uses any helical wire in the hose. The spiral wire used in typical sewer hoses keeps the hose from collapsing but it also leaves a corrugated interior to the hose, which provides restriction when dumping and lots of crannies for waste sediment to pack up inside the hose. This requires additional water to rinse the hose clean. The Viper hose has no wire and the interior is smooth so it rinses clean. You can also step on it to crush it flat and it will bounce right back, unlike a corrugated wire hose which will remain flat and kinked. It also remains flexible at down to -20 degrees Fahrenheit, so it really blows all of the other hoses away.


Sewer hoses, such as this Valterra Viper are available in kits or as individual components.

A Viper 10’ extension hose.

The Viper hose has the ability to be crushed, yet return to its original shape.

Sewer hoses have a male and female bayonet connector so you can connect multiple hoses together if you need additional length. They typically are available in either 10’ or 20’ lengths. I prefer to use 10’ lengths because I can always use two to get to 20’ if I need the extra reach. Plus, I keep a third hose on hand in case I ever have a failure. Various fittings are available to connect to a sewer connection. A campground sewer connection may be as simple as a bare pipe sticking out of the ground or it can be a PVC pipe with either 3” or 4” pipe threads. The most common connector for any RV is a 90-degree elbow with a female bayonet connector to connect to your sewer hose and a long snout to insert into the sewer. Most have a slide-on threaded adaptor that is molded onto the snout. This adaptor has both 3” and 4” male pipe thread so that it can fit either size sewer pipe. If you find you are at a site with a bare unthreaded pipe, you can slide a rubber or silicone donut over the pipe. This will allow you to press the elbow into the unthreaded pipe when necessary. It’s also typically used at a dump station, where the sewer pipe is generally just a hole in the concrete pad. These elbows can also be found in clear plastic so that you can monitor the color of your waste. This is helpful when you are rinsing your black tank and want to know when it is clean. Clear pipes that can be inserted in line with the hose are also available.


A threaded sewer elbow in clear plastic allows you to see when the tank flushing process has been thoroughly cleaned.

90 degree sewer elbows are threaded for various size pipe threads and also a long snout to accept a donut for unthreaded sewer connections.

Sewer hoses do have limited use because they use gravity to dump. If your motorhome’s sewer connection is fairly low and the campground sewer sticks out of the ground quite a bit, gravity isn’t going to work very well for you on this uphill battle. If it’s not too serious, you can just walk the hose from the coach to the sewer after dumping to drain the fluid resting in the hose manually.


Macerators grind up waste and can be portable or mounted in the coach, as in this Entegra.

Macerators use a smaller diameter 1-1/4 to 1-1/2” hose and can pump the waste uphill and for longer distances than a gravity dump 3” sewer connection.

Another option is a macerator. A macerator uses a motor to grind the waste and pump it uphill, similar to a macerator toilet. While a 3” slinky hose has a limited length and cannot go uphill, a macerator uses 1-1/4” or 1-1/2” hose that can pump uphill up to 9’ vertically and 100’ horizontally. Some of these models, such as the SaniCon Turbo, are installed permanently in the RV and feature a 3” bypass port for a slinky. Other models are portable and will connect to the coach’s bayonet fitting on the dump valve wye. They are a bit slower to dump that a 3” slinky but offer the ability to overcome gravity when dumping your tanks.


Dump valves come in 3” and 1-1/2” sizes and are easy to replace. Replacement seal kits are also available.

Operation and Cleaning

Your gray water tank isn’t very fussy. As long as you scrape the heavy stuff off your dishes before washing them and keep from pouring oils and fats down the drain, your gray tank will remain pretty clean. The soapy shower water and dishwater help keep the inside of the gray water tank clean so that your sensors won’t give you any trouble. But your black water tank is a bit pickier, so you’ll need to pay attention to it to prevent any issues from appearing. The biggest problem with black tanks is that the waste can dry and cake up on the inside of the tank walls. This leads to unreliable sensor readings. The most important thing is to keep the waste fluid and don’t let it dry out. Saving water can be a disadvantage in that respect.

It’s possible to use a gravity dump toilet with very little water usage. When the toilet’s blade valve opens, the solid waste and toilet paper can just fall through the gate and lay in a lump beneath if the tank is low on water. With continued use, this “pyramid of death” builds and you’ll need a construction crew to break it up. Avoid this by using plenty of water when you flush the toilet. When you dump the black tank, be sure to add plenty of water to the tank so that you aren’t starting out with a dry tank. This water will help to keep future waste additions soluble. Some users like to keep their gray tank dump valve open, but this can lead to a tank with dry sediment caked in it over time. It also allows for certain insects to leave the sewer and enter the coach – you may wind up sharing a shower with them.

Many black tanks will have a flush mechanism installed. This is basically a spray head that sprays water around inside the tank. In some cases, this sprayer can rinse down any accumulated waste that is caked on the tank walls. In other cases, it’s limited to merely pushing any loose sediment on the floor of the tank to the dump valve. Frequent use of the sprayer whenever dumping the black tank is recommended. If you wait too long, the waste will cake up on the walls and be much harder to remove. If you find that this is the case, it’s best to mix up a solution of Pine Sol and fill the tank to about ¾ full, then drive to your next destination. The sloshing action while driving will help rinse the tank walls and put everything into suspension. Then dump immediately after arriving at your destination and finish off with the tank flushing attachment.


Electric dump valves can be located in hard to access areas, like this Entegra Coach, and can be remotely operated.

Never leave the black tank dump valve open when camping or you’ll experience severe caking and bad sensor readings. Always keep the valve closed unless dumping. It’s a best practice to always dump your gray tank after the black tank. The onrushing flow of soapy gray tank water will help flush any black tank residue from your sewer hose.

If you dump the black tank too often, you’ll never get the water level high enough to prevent waste from caking on the upper portion of the tank walls. Be sure to get the fluid level up high enough before dumping. Ideally, you can do this after a day’s drive to derive the benefit of the sloshing that has taken place. Also be sure to only put human waste and approved toilet paper into the black tank. Never put facial tissue or feminine products down the toilet. You don’t have to buy expensive “official” RV toilet paper from an RV dealer or camping supply store. You just need to use a septic safe paper that will dissolve and break up in water.

You can test your choice of paper by doing the Mason jar test. Place a wad of toilet paper into a Mason jar and fill it about ¾ full of water. Screw on the lid and shake it for about 15 seconds. The wad of paper should now be dissolved into a bunch of fluff suspended in the water. If it is – you pass the test and it’s RV safe. If it’s still a wad of paper and hasn’t broken down – don’t use it in the RV because it will plug up the system.

Chemicals and UViaLite

This brings us to chemicals. A common misconception is that you need to add RV-specific chemicals to treat your waste tank. This is not quite true. Both human waste and toilet paper will dissolve in plain water. You don’t need tank treatment chemicals to do that. If you neglect your black tank, you may need some heavy-duty tank chemicals or Pine Sol to clean it but under normal use, you won’t. One thing chemicals do is deal with odors – although that’s not all it’s cracked up to be either.

Some chemicals are nothing more than perfume. They don’t remove the odors, but they mask it by adding a more favorable scent to the tank. Other chemicals include enzymes that do react with the odors, but enzymes are organic organisms that take 5-7 days to become active. Most RV owners don’t wait that long to dump their tank, so they are basically flushing away good money every time they dump.


Liquid waste digester, such as this Pure Power Blue, will help treat solid waste to prevent clogs and prevent odors.

A great system that I am familiar with is the UViaLite system. I first noticed this system when reviewing an American Coach for a magazine article I wrote for another publication. I also noticed this system on a Thor diesel coach on another article and have since learned that other manufacturers are looking at implementing this system.


This particular bay on an American Coach shows the UViaLite waste tank ventilation system installed.

UViaLite uses proven technology that uses an ultraviolet light set to a specific frequency of 185 nanometers to react with oxygen (O2) to create ozone (O3). This unit picks up fresh air from beneath the coach and passes it through the UV module and into the top of the tank via a 1-1/4” PVC pipe. There are no moving parts because the system uses the chimney effect of natural airflow rising through the tank’s vent stack. 6 to 20 PPM of ozone are created in the unit and the thermal updraft of the vent stack draws the ozone into the holding tank at less than 1 CFM. Once powered up, the unit can remain on and only draws 0.8 amps of 12 VDC power, which is around 10 watts. The unit can remain on until the user stores the RV at the end of the travel season.


This image shows how the UV light creates O3 from O2

Shows how Ozone attacks viruses and bacteria to form oxygen, carbon dioxide and water vapor.

Shows how odors are eliminated by converting the smelly hydrogen disulphide to water and sulfur that settle in the water and oxygen which vents out the stack.

Ozone is a powerful oxidizer that will kill bacteria and chemically destroy viruses in seconds. The ozone generated by the eco-friendly UViaLite attacks the molecular bonds of viruses, bacteria & mold, breaking them up into harmless water vapor and carbon dioxide (CO2). UViaLite removes the stinky smell caused by hydrogen disulfide in the tank by converting it to freshwater vapor and sulfur that falls out of the air and into the tank.


This diagram shows how the air flows through a UViaLite system.

Eliminating odors rather than masking them with a perfumed scent will make a big difference whenever someone flushes the toilet, especially when the bathroom exhaust fan is on. Because it also kills any pathogens, it will prevent viruses shed from a sick person from wafting up out of the tank and possibly infecting other people in and around the coach. UViaLite does not affect anything in the liquid portion of the tank so it won’t affect any chemicals you may have in there. It only affects the air above the liquid, which is where the odor is anyway.

Keep in mind these few tips and you’ll qualify as an RV sanitation expert in no time!

National Indoor RV Centers blogger Mark Quasius profile picture

Mark Quasius is the founder of RVtechMag.com, the past Midwest editor of RV Magazine, writes for numerous RV-related publications and a regular Contributor to FMCA’s Family RVing Magazine. Mark and his wife Leann travel in their 2016 Entegra Cornerstone.

RV Electrical System Failure

RV Electrical System Failure

Sometimes these systems can fail, not that this will come as a shock to anyone. When electrical systems fail it’s time to do some testing to see where the failure is. A voltmeter is a huge help in this area although a test light can also be used to test low voltage circuits. Personally, if you are a motorhome owner you should have a multi-meter of some sort. It’s invaluable for checking high voltage circuits, campground pedestals, low voltage circuits, and continuity.

Fuse Panel

Fuse panels hold fuses for all 12-volt systems

Check for Blown Fuses 

The first thing to do is to check for blown fuses. Sometimes you can do this by removing the fuse and holding it up to the light to determine if the fusible link is blown. Sometimes it’s not so easy to see. The way many of these fuse panels are labeled, or more accurately, “not” labeled, you may have trouble figuring out which fuse does what. The common ATO fuses are blade type fuses with a plastic housing. There are bare spots on the end of the housing that can be used to test for voltage. If you have power going into the fuse, but not out of it, you’ll know you have a bad fuse. Another method is to use the ohms setting on a multimeter. Remove the fuse and check for continuity with the meter. If there is no continuity, the fuse is bad. If you have a critical circuit you can also replace those fuses with ATO style circuit breakers that plug right into place. There are also fuses with LED pilot lights that will illuminate if the fuse is blown. So, you have lots of options when it comes to fuses.


Test for Voltage 

If it’s not a fuse, then you need to look a little deeper. If the fuse does have power leaving it, test for voltage at the device that isn’t working. If you have power coming into the device, it’s either a bad device (light bulb, fan motor, water pump, etc.) or else you do not have a complete circuit. In that case, I’d check for a bad ground because an open ground won’t provide a complete circuit back to the battery. If you do not have power at the device, there is an open circuit between the fuse and the device. The first place to look would be at the switch. Test to see if there is power coming into the switch and power exiting the switch. If the power is getting to the switch but not leaving it, it’s time to replace the switch.

Wire Gauge (AWG) Wire Diameter, in Inches Current Capacity, in Amps
0000 .4600 600
000 .4096 500
00 .3648 400
0 .3249 320
1 .2893 250
2 .2576 200
4 .2043 125
5 .1819 100
6 .1620 65-80
8 .1285 40-50
10 .1019 30-33
12 .0808 20-23
14 .0641 15-17
16 .0508 7.5-10
18 .0403 5
20 .0320 3.3
24 .0201 1.3
28 .0126 0.5

This chart shows the current capacity for various wire gauge sizes

RV Generator Selection

RV Generators: A How-To Guide

Modern motorhomes are packed with the latest technology and household conveniences. Items such as washer/dryer laundry centers, dishwashers, entertainment systems featuring multiple HD TVs, residential refrigerators and electric cooktops all require 120 volt AC power – and that’s in addition to the rooftop air conditioners. 

All of these items operate just fine when you are parked and plugged into a campground pedestal that supplies shore power to the coach, but what happens when you are driving or camping at a location that does not have any shore power? 

Many coaches have inverters that will power some devices, such as a residential refrigerator, microwave oven and entertainment systems. But larger AC power loads can’t be handled by an inverter when driving, such as rooftop air conditioners. Plus, dry camping inverters can draw down your battery bank pretty quickly, so you will need to rely on the motorhome’s generator to provide AC power in order to operate these items and to recharge your battery bank.

Generators come in various forms and sizes, so it’s best to analyze what your power consumption needs and particular applications are when choosing the best generator for you. First, let’s understand a bit how generators work…

Portable- Versus Permanently-Mounted RV Generators

Most larger Class A coaches will come equipped with a generator that is permanently installed in the coach. Larger diesel pushers generally have them installed in the nose of the coach and are mounted on a slide-out rail for ease of service. Gasoline powered motorhomes that are of a front engine design will have them installed in a side compartment, or may even be an optional feature.

National Indoor RV Centers blog RV Generator in Class A motorhome

Generators such as this 5500 watt Onan Marquis Gold gasoline powered generator are commonly mounted in a basement compartment on gas powered class A motorhomes.

Installed generators have the benefit of using the same fuel tank that feeds the engine. The output wiring is connected to an automatic transfer switch, making it a simple task to start the generator via a switch in the motorhome’s interior. Smaller Class C and Class B motorhomes are limited on storage, so a generator is often an option not chosen by the buyer, opting instead for more storage space. In that case, a portable generator might be a better choice.

National Indoor RV Centers blog-RV-compact-generators-Class C-Class B motorhomes

Compact units – such as this 4,000 watt gasoline powered Onan – are typically installed in Class C or B+ coaches where basement cargo space is limited in height.

Portable generators won’t tie up your RV’s basement storage space, but you will have to find some place to carry it, like in the back of a pickup bed. They can multitask, so you can use the generator in other locations without the RV. You can even use it to provide emergency power during an outage at your home. One drawback is that you need to carry a separate fuel supply for the generator, which also requires storage. Weight is also a consideration because the need for horsepower increases as the wattage demand goes up. More horsepower means larger engines that are heavier, making the generator harder to handle.

National Indoor RV Centers-blog-RV generators-portable generator for motorhome use

Units such as this Honda 5,000 watt are portable and can be moved by two persons.


 Household power in North America is 60 Hertz – which is the measurement of the power’s frequency or wavelength per second – while electrical power in Europe is 50 Hz. Any electrical device designed for use in North America will require 60 Hz power in order to operate. Frequency in a generator is determined by the number of times a magnetic field passes by a generator’s stator winding and receives an induced charge. In a generator with two field coils, the generator needs to spin at a constant 3,600 RPM in order to create 60 Hz power while a generator with four field coils only needs to run at 1,800 RPM.

Most portable generators are of the two pole design to save weight on both the engine and the generator itself. For example – a 3,500 watt generator will require around 8 HP to generate that much electrical power. A typical 8 HP engine will produce that power at peak RPM, which is going to be close to the 3,600 RPM that a two pole generator will operate at. A four pole generator will only need to turn at 1,800 RPM to achieve 60 Hz, but a four pole generator is heavier and bulkier and the engine won’t be able to create its maximum rated power at that slower speed. Therefore, a large engine rated in the 12-14 HP range at 3,600 RPM will need to be used so that 8 HP is still available at the lower 1,800 RPM. The extra weight and size of the larger engine and generator doesn’t make it a good choice for a portable generator but is best suited for a stationary mount where the quieter operation associated with lower RPMs is beneficial.

Split Phase Versus In-Phase:

Regardless of whether your generator is a two pole or four pole unit, there will be two field windings that provide power to the receptacles. Each winding is capable of producing 120 volts of AC power at one half of the rated capacity of the generator. These windings can be connected in series to offer 120 or 240 volts in a split phase design, or in parallel to offer only 120 volts in what is referred to as an in-phase design. For example – a 6,000 watt generator has two field coils, each with 3,000 watts of available power at 120 volts. Referring to the graphic below, we can see that there are 6,000 watts of 240 volt power available between L1 and L2. There are 3,000 watts of 120 volt power available between L1 and Neutral, and another 3,000 available between L2 and neutral. 3,000 watts at 120 volts is only 25 amps. Unfortunately, you can’t draw 30 amps on one circuit because the two fields are in series.

National Indoor RV Centers blog RV Generators split phase wiring

The graphic referred to in the text as the Split Phase diagram

The split phase system works fine on larger generators, such as 10,000 watts and up, but has its limitations on smaller units. Many of the smaller units used in RVs do not have 240 volt capabilities, which is fine because 240 volt appliances in an RV are extremely rare except for very high end coaches. In this case, the two windings are placed in parallel rather than series. This eliminates any 240 volt capability but allows for the full 6,000 watts to be available on any one circuit. This is referred to as an in-phase system and is generally used on generators rated at 7,000 watts or less. 

Inverter Generators

Inverters are the opposite of converters. A converter takes 120 volt AC power and converts it to 12 volt DC power to operate lights, water pumps, fans and other 12 volt accessories in the RV as well as battery charging power. An inverter takes 12 volt DC power from the batteries and inverts it to create 120 volt AC power. Small inverters can be used to power an entertainment system while larger inverters can power a number of receptacles and appliances. This means you don’t have to run your generator to keep a residential refrigerator cold while driving and can also operate a microwave and a few outlets. They are helpful because it extends the time interval between times when you need to run the generator to recharge batteries or run larger loads.

National Indoor RV Centers-blog-RV generators-inverter- based-Honda 2200-unit

An inverter based Honda 2200 watt unit.

However, inverter technology has also filtered into generators as well. Inverter based generators are popular in some of the small portables, such as the Honda EU2200 series as well as in the Onan Quiet Diesels in the 7KW to 8KW range. In a sense, these generators are not true AC generators, although their eventual output is AC power. They are actually DC generators that send their variable DC output through inverter circuitry built into the generator itself. This eliminates the requirement to operate at a steady 1,800 or 3,600 RPM because the inverter electronics convert the DC power from the generator into 120 volt AC power and establish a 60 Hz frequency electronically. 

A DC generator has no requirement to turn at any given speed because the output power increases as the generator’s speed increases. This allows the generator to operate at a lower RPM under light loads, saving fuel and reducing the noise level. 

As you add more demand for power, such as when an air conditioner starts up, the generator’s speed will increase to raise the power output level, all the while maintaining a steady 120 volt AC power level at a 60 Hz frequency. Inverter based generators also put out fairly clean power with low levels of noise or total harmonic distortion (THD), which is a benefit when powering sensitive electronic equipment. Inverter generators are not found in the larger 10KW  sizes and up because the inverter boards would be large and expensive and generally not necessary with the stability present in the larger diesel generators. However, they are quite popular in the smaller portable models.


When selecting the proper size generator, it’s important to remember that wattage is the measurement of true power. A 50 amp shore power supplies 50 amps of 120 VAC power on each leg. “Amps” x “volts” = watts, so a 50 amp shore power receptacle is capable of providing 6,000 watts power on each leg, for a total of 12,000 watts. Therefore, if you want a generator that can match that power, you’ll need a 12,000 watt generator. If you don’t use all of that power, you may be able to step down to a 10,000 watt generator, but the biggest factor is with air conditioning. A coach with two rooftop air conditioners may be able to get by with a 7,000 watt generator, depending on how many other 120 volt accessories you have. But any coach with three rooftop units is going to need at least 10,000 watts.

 When sizing up a generator, you need to consider how your loads are distributed across the breaker panel. A split phase generator can only supply half of the total capacity on each leg, so you have to be sure that your heavy loads are evenly distributed across both legs of the panel. Remember that each leg has a given amount of amperage and on a split phase generator, they cannot be shared. If your loads are imbalanced, you’ll need a much larger generator just to feed one leg while the other leg is not being fully utilized. 

Another consideration is static versus dynamic loads. Lighting and heating elements are static loads in that they always consume the same amount of amps. Dynamic loads are associated with components that have load requirements that vary under different conditions.

Motors are considered dynamic loads because the current draw varies according to how hard they are working – plus, they generally have a startup surge which can be up to three times the running load. Consider the case of an air conditioner. It may have a typical unloaded draw of less than 10 amps, but when it first starts up it will have a surge of in excess of 20 amps as the capacitor start motor starts up against the head pressure in the refrigerant. If the unit was resting long enough, it may settle in to around 10 amps immediately after startup but as the head pressure increases and the unit works hard, it can draw 12-14 amps. Consider that you most likely won’t be starting all three air conditioners at the same time so you don’t need to use the peak starting surge for every unit when calculating how large your generator needs to be. Remember that “volts” x “amps” = watts, so just multiply your amps by 120 to convert to watts in order to determine how many watts you’ll need. 

Following are some examples of typical load requirements:

Air Conditioners 1400-2000 watts
Refrigerator 600-1000 watts
Electric Frying Pan 1000-1500 watts
Electric Stove Element 675-1000 watts
Electric Water Heater 1250 watts
Hair Dryer 500-1500 watts
CRT Television 200-600 watts
LED Television 100-375 watts
Portable Ceramic Heater 750-1500 watts
Toaster 1000 watts
Satellite Dish and Receiver 200 watts
Battery Charger/Converter 750-1400 watts

When sizing your generator, you also need to consider the fact that altitude affects the engine’s ability to create power. Different engines react in varying amounts. An Onan Marquis Gold series of gasoline powered generators will lose 3.5% of power for every 1,000-foot gain of altitude over 3,000 feet. The Onan Quiet Power Diesel 10,000 watt will derate 3.5% for every 1,000’ over 500’ of altitude and it further derates by 1% for every 10oF of temperature increase over 85oF. This equates to a 7,500 watt generator running at 9,000’ of altitude that will only be capable of handling 5,000 watts at that altitude unless the engine has enough excess horsepower to allow for it.

National Indoor RV Centers-blog-RV generators-diesel generator

Most Class A diesel pushers have diesel powered generators, such as this Onan 10,000 watt installed in the front cap area of a Newmar London Aire are placed on slide-out rails for ease in service access.

Diesel engines are pretty much capable of handling the fuel injection requirement at higher altitudes but carbureted gasoline powered engines will have issues with running rich due to lack of air. Some generators, like the Onan Marquis Gold series, have a mixture adjustment on their carburetors. You can adjust the fuel flow with a lever to lean the engine out when operating at higher altitudes. But be sure to reset it to the full rich position when you return to the flatlands or else you run the risk of burning valves by running the engine too lean.

Armed with this information, you should be ready to select the best generator for your RV lifestyle. Be sure to include your generator when you have your RV tech perform scheduled maintenance on your motorhome. Taking care of it will ensure it will take care of you when you need it.

Supplemental RV Braking Systems

Towing without a supplemental braking system is dangerous RV driving

A motorhome is an excellent choice for traveling. Everything is self-contained and you have the comfort and security of sleeping in your own bed and cooking your own food. The only caveat is that they are large, so using it as a daily driver to go shopping or sightseeing in a national park just doesn’t work out very well. Fortunately, motorhomes are equipped with trailer hitches, making it easy enough to tow a smaller vehicle for your touring while the motorhome is parked at your campsite. Towed vehicles can include a vehicle placed on or in a trailer or loaded onto a tow dolly, but the most common method is to use a tow bar to flat tow your vehicle – commonly referred to as towing four-down.

There are a number of vehicles capable of being towed four-down but there are exceptions, so you’ll need to check with your manufacturer to see if your choice is flat towable. If it is, the next step is to verify that your coach is capable of towing your vehicle of choice. Larger Class A coaches have ample capacity, and some can tow as much as 20,000 lbs. but some smaller Class C motorhomes may only have a 3,500 lb. towing capacity, which will limit you from towing any vehicle that exceeds that weight rating.

In addition to the rating stamped on the trailer hitch, you’ll also need to look at the Gross Vehicle Weight Rating (GVWR) and the Gross Combined Weight Rating (GCWR) of your motorhome. The GVWR shows you the maximum amount of weight that the motorhome can safely weigh. The GCWR indicates the maximum safe weight of both the coach and any trailer or towed vehicle and will always be higher than the GVWR. For example: if you have your coach loaded to the maximum GVWR (let’s just assume 32,000 lbs. as an example) and your GCWR is rated at 36,000 lbs. it leaves you with 4,000 lbs. as the maximum safe weight of the towed vehicle or trailer. Your trailer hitch may be rated at 10,000 lbs. but you must limit the towed weight to the lesser value of the hitch rating or GCWR. If you do not load your coach to the maximum GVWR, then the difference between the GCWR and your actual coach’s weight when fully loaded will increase and you may be able to tow a bit more than the 4,000 lbs. in the above example.

The GCWR also assumes that you have brakes on whatever is being towed. If you have an enclosed or flatbed trailer it will most likely have brakes on those axles that are designed to work in conjunction with a brake controller in the tow vehicle. As long as you have installed a trailer brake controller in your motorhome, you’ll be fine. But when you flat tow another vehicle – it’s a different story. A car, Jeep or truck has its own braking system that is controlled by the driver when driving that vehicle. When you hook up to a motorhome to flat tow the braking system on the motorhome and the braking system on the towed vehicle are two separate entities. They do not work together, so you have no towed vehicle brakes when towing.

Fortunately, there are a number of third party supplemental braking systems on the market that will allow you to safely tow your vehicle and be compliant with the GCWR requirements.

Questions sometimes arise as to the legality of towing without a supplemental braking system, which varies according to state or province. I’ve also heard a few arguments from RV owners about not spending the money on a supplemental braking system because “you can hardly feel the towed vehicle behind the coach”. While the towed vehicle is a small percentage of the total weight, especially on a large tag axle diesel pusher, tests have proven that there still will be a difference in stopping distance during a panic stop. A study taken by Roadmaster and published on their website showed a 34’ class A motorhome took 132 feet to come to a complete stop from 50 miles per hour. When a medium size car was connected to the motorhome the stopping distance increased to 209’. When a supplemental braking system was added to the towed vehicle this distance decreased to 137’. Those extra 72’ can make the difference between safely stopping in time or being involved in an accident should an emergency stop be required.

Another reason for a supplemental braking system is to protect yourself and others during a breakaway situation. Some systems include this and some offer it as an optional accessory, but in either case this is something that every supplemental braking system should have. A breakaway system consists of a switch that is mounted on the towed vehicle and is connected to the coach via a small steel cable. Should the towbar fail or for any reason the towed vehicle becomes disconnected from the coach while driving, the cable will activate the breakaway switch and the supplemental braking system will apply the towed vehicle’s brakes to safely bring the vehicle to a stop and prevent a runaway that could possibly impact another vehicle.

I recall one incident I experienced where a supplemental braking system with breakaway device saved me from some major damage. I had recently rebuilt my towbar and decided to replace my locking towbar and hitch pin set while I was at it. Shortly after we left for a long trip and not more than an hour down the road, I heard and felt a large jerk on the back of the coach. I looked in my rearview camera and saw that our Jeep was following us about 10’ back from the coach. I knew that something had failed in the towbar, so I pulled over to the side of the road and got out to investigate. I saw that the main 5/8” hitch pin that holds the towbar into the coach’s hitch receiver had failed, allowing the tow bar to pull out of the hitch and drag along on the ground. The safety cables held and kept the Jeep behind me and the breakaway cable applied my M&G supplemental braking system on the Jeep, keeping it at a distance from our coach. Had I not had a breakaway system, our Jeep would undoubtedly have plowed into the back of our coach once I attempted to slow down, damaging both the front of the Jeep and the rear of the coach. Our safety cables were stretched beyond being useable but I had kept the old set of locking hitch pins and a spare set of safety cables along, so I replaced them, reconnected the towbar and happily went on our way with no damage to either vehicle.

Types of Supplemental RV Braking Systems

Supplemental braking systems are available in several different versions. Some systems are portable and can be taken out of the vehicle when not needed while other systems are permanently installed into the vehicle. In either case, these systems will provide supplemental braking ability to the towed vehicle. Both methods have pros and cons so let’s look at the differences and see which method works best for you.


Demco’s Delta Force is a portable system.

Portable systems are placed upon the floor of the driver’s footwell. They operate by actuating an arm that clamps onto the brake pedal. These units use 12-volt battery power to actuate the arm that connects to the brake pedal and use decelerometers to detect when the vehicle is decelerating. The main module is a box that contains the mechanism and sensors and rests on the floor, but generally must be placed against the driver’s seat so that the box stays in place when the brake pedal arm extends so that the box doesn’t move instead. Some of these systems may have additional brackets to help keep it from sliding while others simply rely on the seat cushion to prevent it from moving rearward when the brakes are applied. If you want a portable, you’ll have to consider how soft your seat cushion is and whether that will affect your choice of portable braking system. Popular systems are available from a number of manufacturers, such as Blue Ox’s Patriot 3 system, Brake Buddy’s Classic 3 and Select 3 systems, Roadmaster’s Even Brake system and Rvibrake’s Rvibrake 3.


Blue Ox offers the Patriot 3, which is a portable unit that is placed on the driver’s footwell and connects to the brake pedal. It can easily be removed and stored or transferred to another vehicle.

Roadmaster’s Even Brake is another portable braking system that can easily be transferred from one vehicle to another.

Another caveat to a portable system is that they still do require some installation, so you can’t just drop it into any vehicle and expect it to work. You will need to mount a breakaway switch to the front of your vehicle and run its wires back to the footwell where they will plug into the brake controller. You’ll also need to provide a 12-volt power receptacle to plug the unit into. Many cars will have a 12-volt receptacle that is connected to the ignition key switch. That won’t work because the receptacle will not have any power when you are towing. You may have to install a constant-hot receptacle someplace in your dash area.

While these installation tasks are minor compared to a system that is permanently installed, you still have to deal with setup every time. This begins by placing the unit on the floor and connecting the clamp on the arm to the brake pedal. Then plug in the breakaway wires and power cord and position the unit so that it can’t move backward when the brakes are applied. You may also have a calibration routine to go through, depending on the manufacturer of your braking system. Once you are done towing you will have to disconnect the wires, remove the clamp from the brake pedal and find someplace to store the system.

The last consideration is that these systems use sensors to sense when the vehicle is decelerating because there is no communication between the towed vehicle and the coach. If you are using the coach’s Jake brake to slow down when descending a downgrade, the supplemental system will unnecessarily apply the brakes on the towed vehicle because it assumes you are braking. This can result in excessive wear and heat buildup when traveling in the mountains.


NSA’s Ready Brake mounts to your hitch receiver and acts as a surge brake with your tow bar.

A system that is permanently installed takes a bit more labor to install but, once installed, it’s pretty much a hands-off forget-about-it system. The simplest is NSA’s ReadyBrake, which is permanently attached to the towbar. This is basically a surge brake system that senses the forward pressure of the towed vehicle under braking. As the module moves, it pulls on a steel cable that runs through the towed vehicle’s engine compartment to the area around the brake pedal. This cable attaches to the brake pedal and applies pressure to the pedal in response to the pressure applied to the towbar mounted actuator.

A number of popular systems are available for gasoline powered motorhomes. These use an actuator that attaches to the towed vehicle’s brake pedal, generally via a cable. The cable is behind the brake pedal so it doesn’t get in the way when driving the vehicle. Most use a decelerometer sensor to sense the rate of deceleration but are also connected to the motorhome’s brake light switch so that the brakes will only apply when the driver steps on the brake pedal in the motorhome, preventing any brakes from dragging when descending steep grades. Common systems include Brake Buddy’s Stealth system which is a dual-mode system that can also use the cockpit-controlled module to actuate trailer brakes as well as towed vehicle brakes.


Brake Buddy’s Stealth is a dual mode system that can be used to activate trailer brakes as well as towed vehicle brakes.

Other systems are Roadmaster’s InvisiBrake and Demco’s Stay-In-Play Duo. These systems can be used on diesel powered coaches as well, but they lack the true proportional braking available from a system that is designed for a coach with air brakes.


Roadmaster’s Invisibrake is an excellent choice for coaches with hydraulic brakes. The controller can be mounts in any location and once set, does not need any further interaction.

Demco’s Stay-In-Play Duo utilizes a small module that mounts in the engine compartment and utilizes a cable attached to the brake pedal arm to operate the brakes. It’s a good choice for coaches with hydraulic brakes.

With a diesel-powered coach that has air brakes, you have lots of choices. If you recently upgraded from a gasoline-powered motorhome to a diesel pusher, you can continue to use your existing towed vehicle’s braking system. Or, you can upgrade to a pneumatic system that utilizes the air pressure from your coach’s air brake system to apply the brakes on the towed vehicle. The biggest benefit is that you can now get true proportional braking because the brakes on the towed vehicle will apply in the same amount and at the same time as the brakes on the motorhome. The harder you step on the coach’s brake pedal, they harder your towed vehicle’s brakes will apply. You can now coast and descend grades without any worry about prematurely applying or dragging the towed vehicle’s brakes.

These systems involve the installation of a module under the hood that generally actuates a cable that pulls on the back side of the brake pedal arm. This module connects to 12-volt battery power to operate the breakaway valve and in some cases will operate a vacuum pump to provide a source of vacuum to the brake booster behind the master cylinder so that the power brakes are in operation. A pair of wires runs to the front of the vehicle and connect to the breakaway switch while a small air hose also runs to that area to serve as a connection to the coach’s air brake system. In addition to the usual trailer light umbilical, a steel cable for the breakaway switch and an air hose are also used to connect to the rear of the coach.

Some diesel pushers come from the factory prepped for supplemental braking systems and have a quick disconnect coupler at the rear of the coach. If not, you can get a DOT approved kit to allow your diesel chassis to do that. You can’t simply tee into a brake line some place or you may risk a loss of brake pressure on the coach should the air hose to the towed vehicle fail. These systems will add a small air tank and the necessary valves to isolate the towed vehicle’s supplemental braking system from the coach’s brake system to prevent any failure from affecting the braking of the coach. The most popular pneumatic true proportional systems are the M&G Tow Brake and Demco’s Air Force One.


Demco’s Air Force One uses a compact air operated cylinder that is connected to the brake pedal arm and uses the coach’s air supply to operate.

SMI’s Air Force One has a central controller unit that operates the air cylinder.

Note that either of these systems can be used on a gasoline-powered coach but it requires the purchase of an installation kit which includes a 12-volt air compressor that converts hydraulic brake pressure to pneumatic so that you can deliver true proportional air to the towed vehicle. These optional kits are a bit pricey but do give you true proportional braking and your towed vehicle will be ready for a diesel pusher if you decide to upgrade later on.


The original M&G Tow Brake is completely contained within the towed vehicle’s engine compartment and uses coach air pressure to provide true proportional braking. The module is inserted between the vacuum booster and brake master cylinder for failsafe operation.

The M&G 2.0 Tow Brake uses a remote air cylinder with cable to operate the brake pedal.

Selecting the correct system will depend on your needs. If you tow multiple vehicles and don’t mind living with the lack of true proportional braking and storage issues, then a portable system might be your best choice. If you want an “install once and forget about it” system, a permanently installed system should be your choice. If you are reasonably talented, you might make this a DIY installation but if not, you’ll want to have it done correctly by a certified chassis tech, such as those at National Indoor RV Centers. Electrically operated systems can be used on both gasoline- or diesel-powered coaches while pneumatic systems that tap into your coach’s air brake system can give you true proportional braking that will match the application of your coach brakes and prevent any false readings that can occur from inertia sensors used on many electrically operated systems.

Regardless of which system you prefer, it’s important to have a good supplemental braking system with a breakaway switch to be safe when towing. Towing without one is dangerous and is tantamount to driving without insurance and throwing out all your fire extinguishers. It’s just not an area to ignore.

National Indoor RV Centers blogger Mark Quasius profile picture

Mark Quasius is the founder of RVtechMag.com, the past Midwest editor of RV Magazine, writes for numerous RV-related publications and a regular Contributor to FMCA’s Family RVing Magazine. Mark and his wife Leann travel in their 2016 Entegra Cornerstone.

RV Electricity

RV Electricity

Understanding the basics of RV electrical systems is important to every RV owner. The electrical system of a motorhome can be quite complex, involving 12 volt DC battery power as well as 120 volt AC power. It’s unavoidable that issues will occur from time to time but many of these can easily be corrected by the RV owner with a basic understanding of electricity. Without this knowledge it can be a daunting task to track down and correct any electrical issues but knowledge is power (pun intended) so this tutorial will help you to better understand how your motorhome functions by teaching you the basics of electricity and how to apply that to your motorhome. 

AC vs. DC in RV’s

It’s important to know the difference between AC and DC power when working with your RV electrical system. AC, alternating current, and DC, direct current, both work together to power your RV. While the AC system is powered by an AC power source, the DC system runs off one or several battery systems installed in your RV. The AC system powers appliances like microwaves, air conditioning, and any power outlets, whereas the DC system powers your water, fans, lights, and TV. Generally, the AC system can generate more power than the DC system because of the RV battery limitations. 

RV Split Phase

Most larger motorhomes now come with a 50 amp service while older motorhomes came with 30 amp services, as do many of the smaller towable RVs. Over the years a lot of amenities have been added to motorhomes. As washer-dryers, multiple air conditioners, larger refrigerators and other large accessories are added the power requirements also increase. But not every RV park has upgraded their electric supply to accommodate today’s electrical demands. Sometimes certain areas are set aside with 50 amp service while others still have 30 while some parks have upgraded their power grid properly. Because there needs to be compatibility with all RVs a multi-outlet pedestal is usually installed that will supply a 50 amp service, a 30 amp service, and even a 20 amp duplex receptacle for the smallest power requirements. A cutaway image of a typical power pedestal is shown below.

Power Pedestal

Power Pedestal

In the above pedestal image we can see three separate outlets. From left to right they are 50 amp, 30 amp, and 20 amp. Each receptacle has its own dedicated breaker sized for that particular outlet. This gives the RV owner the choice of choosing whichever outlet they need to best match their RV’s electrical service. 

Split-Phase Service

But, before we delve into the available services we first need to understand what a split-phase service is. 

120/240 Volt Split Phase service wiring diagram

When you create electrical power there is always a pair of windings in the generator that power is taken from. This is true whether it’s a small portable generator, a large diesel powered RV generator, or a huge megawatt generator at your local power utility. These two windings are connected together in series and a tap is run into their common center connection. 

In the above diagram we can see that the ends of these windings are identified as L1 and L2. The common center tap of these two windings is identified as N while L1 and L2 are the hot leads brought into your breaker panel at home and each is generally referred to as a “phase”. The N is the Neutral wire that goes to the neutral buss connection in your breaker panel. This is exactly the same way that your RV’s breaker panel is configured. If you put a voltmeter across lines L1 and L2 you’ll see 240 volts. But if you test L1 to N or L2 to N you’ll see 120 volts. Your breaker panel at home is wired so that every other slot is on a different phase and most RV breaker panels are wired the same way. 

The hot lead runs to whatever device you have on that circuit and the white neutral wire returns back to your panel’s neutral buss bar so that you have a completed 120 volt circuit. If you put a two pole breaker in you’ll be grabbing one of each phase so that 240 volts is sent to and from that device. 240 volt devices don’t require a neutral wire because the power runs from L1 to L2. So just how does this power flow? 

Earlier we talked about how AC power just shuttles back and forth. Well, all of the power in this panel leaves one phase and returns to the other. This is easy to understand if it’s a 240 volt load because the power leaves L1 and goes to L2 but it’s not as readily apparent when on 120 volts because the neutral can be misleading. With 120 volt circuits the power leaves one breaker, for example the L1 pole, and travels to the load. It returns via the white neutral wire to the neutral buss bar. If this is the only thing running in that panel the current will then get drained back to the power utility via the service’s neutral wire. But, if there are loads running that reside on the other side of the breaker panel, then this is not true. 

Electricity always follows the path of least resistance. In the case of an electrical service it always tries to go between L1 and L2 whenever possible. If you have a 20 amp load on a 120 volt L1 breaker and a 15 amp load on a 120 volt breaker on L2, 15 amps of power will shuttle back and forth between them, using the Neutral buss bar as a connector between them. They will be in balance and your ammeter will read 20 amps when testing on L1. When you test on L2 you’ll see 15 amps showing on your meter. If you were to clamp your meter onto the neutral wire you would see 5 amps displayed because the neutral wire only carries the imbalance between L1 and L2. If you had 20 amps running on each phase you would see zero amps on the neutral line. That’s because the AC power tries to shuttle back and forth between L1 and L2. That is what is called a balanced load. You try to achieve this when arranging your breakers in the panel because it minimizes the current flowing through the power company’s electric meter but that’s not always possible. If everything was on one side you’d be pulling 40 amps on one phase, zero on the other, 40 amps on the neutral, and 40 amps on the electric meter so you try to balance things as much as possible. 

Now that we know how the breaker panels are normally set up and how the power company sends its power, we need to figure out how this relates to our RV. RV’s rarely have any 240 volt items in them. Many of the larger RVs have 50 amp services, which are a 120/240 volt split phase system. But before we look at the 50 amp service let’s first look at the 30 amp service. 

30 Amp Service:

A 30 amp RV service is really just a glorified 120 volt single pole outlet. Electrical outlets are labeled with a NEMA code designation and the 30 amp outlet used in RV pedestals is designated a NEMA TT-30R and the plug is a TT-30P. The TT stands for Travel Trailer and is an RV specific receptacle so you won’t be finding this outlet in any residential environment. The P and R stand for Plug and Receptacle respectively. This is a 3 prong plug that consists of a 120 volt hot wire, a neutral wire, and a safety ground wire. The 30 amp RV receptacles do not use GFCI protection. If you have an older or smaller RV you most likely have a single pole 30 amp breaker panel where everything is on one phase. There’s no need to split breakers on a 30 amp panel because there is only L1 and 120 volts present. If you need to plug in at a location where there is no 30 amp RV style outlet you can buy a 15-to-30 plug adaptor at any RV dealer that will adapt your 30 amp RV plug to a standard 15 or 20 amp duplex receptacle. This is the way that RVs were made for many years but with today’s modern amenities it has become necessary to increase the power supply to the newer coaches. Keep in mind that 30 amps times 120 volts equals 3,600 watts and that is how much “stuff” you can operate until you run out of power. 

50 Amp Service: 

To facilitate the larger loads placed upon the newer RVs the 50 amp service was brought to the RV world. Whereas the 30 amp service was a 120 volt service yielding 3,600 watts of power, the 50 amp service is a 120/240 split phase service. The split phase service means you have two 120 volt 50 amp poles, which gives you a total of 12,000 watts. So the perceived increase from 30 to 50 doesn’t sound like very much but the real increase from 3,600 to 12,000 puts it into a more realistic perspective. Keep in mind that this assumes that you can utilize both of the two 50 amp poles effectively by balancing your load. If all of your loads are on one side of the panel you’ll only be using one 50 amp pole, which means that you can only get 6,000 watts. So, it is important to split your loads and balance them between both phases on the breaker panel in order to get maximum capacity. 

Very rarely will an RV have any 240 volt loads. Some RVs may have 240 volt stackable clothes driers or an electric heating element of some sort but it’s rare. Still, the ability to split the load among two poles means that each pole can handle 50 amps. If all of the circuits were placed on a single phase, as in the 30 amp service, then you would need a 100 amp service to provide that same amount of power. That would require some massive wiring to the pedestal and also some very fat and heavy power cords to the RV. A 50 amp split-phase system lets you get that higher wattage with a smaller #6 gauge wire. But what happens when you have an RV with a 50 amp power cord but the campground only has a 30 amp service at the pedestal?

30-to-50 dogbone adaptor

30-to-50 Dogbone Adaptor

At times it becomes necessary to power an RV with a 50 amp service when there is no 50 amp NEMA 1450R receptacle available. Unlike the 30 amp NEMA TT-30R, the 50 amp outlet isn’t an RV-only receptacle so it can be found in residential and industrial applications as well and has a 4 prong outlet that has two hot wires – L1 and L2, as well as a neutral and ground wire. Any RV dealer or RV accessory store will offer an adaptor that is commonly referred to as a 30-to-50 dogbone adaptor, which is illustrated above. This adaptor will let you adapt your 50 amp plug to a 30 amp so that you can plug your 50 amp RV into a 30 amp RV receptacle if that’s all that is available. When you do this you’ll be limited to 30 amps of power though. The dogbone adaptor will connect the single 120 volt hot pole to both the L1 and L2 inputs of your RV’s 50 amp breaker panel. When you do this you will have the same phase across L1 and L2 so there will be no 240 volts available. But, seeing as how 99.9% of the RVs made don’t use anything with 240 volts, that’s volts that’s not a problem. 

In this situation all of the power will be going down the neutral wire. But, you are only sending 30 amps to the panel and your neutral wire is rated to handle 50 amps so you’ll be fine. You will have to be careful to manage your loads when running on 30 amps. If you fire up all of your air conditioners and water heater you are going to trip that 30 amp pedestal breaker real quick so you have to watch what you turn on. You can also add a second adaptor to change the 30 amp down to a 20 amp plug if you have to but then all you’re going to be able to do is keep the batteries charged and maybe run a few lights.