Mod #9: Generator Install

Mod #9: Generator Install

Submitted on: 06/13/08

     Category: electrical
Mod Rating: 12345

(53 ratings)

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Mod Description:

There are many options for powering your RV when you don’t have hookups, from the basic battery to the full-blown hi-tech solar/inverter/giant battery bank setup. One of the most convenient options is a generator. While generators can be an expensive investment, always having power, whether day or night, is worth the cost to most.

Mod Difficulty:

Most class A and class C motorhomes either come standard with a built-in generator or are pre-configured to accept one. 5th wheels and toy haulers also can come from the factory with a generator, although it is generally an option rather than a standard. Travel trailers have fewer options and don’t typically, save for a few manufacturers like Arctic Fox, have provisions for a generator. But since we are talking about modding your RV, no RV has to go without a generator.

Installing a generator in an RV that is not equipped for one is a daunting project. Even if you have provisions for one, things like mounting, cooling, wiring, fuel supply, exhaust routing, noise and vibration, and accessibility all need to be seriously considered and planned for. But not to worry. Many RVers have already done this mod with great success. Some have even gone as far as retrofitting portable generators that were never designed to be mounted to or in an RV.

If you are fortunate to have an RV that is “generator-ready”, your options are straightforward. There are basically 4 manufacturers that make RV-style generators: Honda, Generac, Onan, and Kohler. There are others but these are the most popular. Of these, Onan is by far the most prevalent in factory installations. Onan not only makes the generator but also the kits, including mounting brackets, wiring, and exhaust. This makes for very clean and easy installation. The other manufacturers also provide installation kits as well. If you are doing a custom install, some of the parts included in the installation kits can still be useful. For example, if you build out a custom enclosure from one of your storage compartments, the mounting bracket can simplify any custom welding for the frame mounts.

Supplying fuel to the generator can be problematic depending on the type of RV. Class A and class C motorhomes share the fuel supply already on-board, whether diesel or gas. Toy haulers will have a fuel tank installed as part of the generator option, which doubles as a fuel station supply for filling up the toys you haul. It’s when you are doing a custom install that you must decide on the fuel to use. Some opt to use the on-board propane which is a very clean burning source. Choosing propane however has two drawbacks: 1) There is a limited supply which isn’t easily replaced if you’re boondocking, and 2) Using propane derates the power output of the generator around 10% or so. Something to keep in mind if you size the generator just at the edge of your power requirements.

If you choose not to use propane as a fuel source, you must retrofit a gasoline fuel tank. There are gas tanks purpose-built for custom mounting, which include a fuel supply outlet, vent, fuel level sending unit, and fuel filler provisions. Select the largest fuel tank that you can reasonably fit to your RV. This way you won’t be worrying about running out during an extended boondock. You should also consider how you move the fuel from the gas tank to the generator. Some generators have a low-pressure fuel pump built in but others may not. If you have to install a fuel pump, be sure to consider how you will power it and use high-quality fuel hose. Don’t compromise here.

Sound deadening is another area many have spent considerable amounts of time on. Most factory generator installations have very little to no sound deadening material at all. Basically, you get a sealed (to the inside of the RV) enclosure made of galvanized steel and, well, that’s it. A lot of sound is transferred in to the RV through the thin metal. Lining the top, sides, and back of the compartment with layers of differing sound deadening material seems to have the greatest effect. With a custom installation, you may have to experiment on what works best for your particular compartment fabrication situation.

Another consideration with a custom install is routing the exhaust. If it’s possible, try mounting the generator on the left or street-side of the RV. This way, the exhaust smell and generator noise will be reduced and will make sitting outside on the entry-side of the RV more comfortable. However, your camping neighbor may not appreciate this as they will get the brunt of the noise and smell. Routing the exhaust out the back side of the RV may be a better choice if you camp in close side-by-side quarters. Ensure you use the appropriate size exhaust tubing too so as to avoid excessive back pressure and possible overheating of the generator under heavy load.

Cooling and ventilation is also very important to account for to ensure proper operating temperatures. In a custom install, there needs to be a way to get cool air in and hot air out. RV-specific generators will have this solution already built in to the generator housing. However, putting this type of generator in an improperly ventilated compartment will overheat the generator in short order. Ensure the access door to the generator has an adequate fresh air opening sized to the generator requirements, and ensure the hot air can be exhausted out the bottom of the enclosure. This can be accomplished using an electric fan with enough flow to suck out the hot air produced by the engine-driven cooling fan.

Wiring for the generator will depend on how “automated” you want the system to be. Plugging the shore power cord directly in to the generator receptacle is the easiest way to ensure you cannot have both shore and generator power simultaneously being supplied to the RV. However, doing it this way can limit you to running the generator only when the RV is stationary as you wouldn’t want your shore power cord dangling in the wind while plugged in to the generator going down the road!

Another wiring option is to use a transfer switch. This device allows two sources of AC power to be connected at the same time to the RV, but only one source is used at a time. The generator AC output is wired in to “one side” of the transfer switch and shore power is wired in to the “other side”. A single AC output from the transfer switch provides the AC input to the RV load center. A relay inside the transfer switch then switches between the two sources as appropriate, ensuring fireworks only happen on the 4th of July.

You will have to have some way to start the generator. Installing a remote switch that can be used from inside the RV is optimal but most electric-start generators can be started from the generator itself. Do not use your RV battery as a starting battery for the generator. RV batteries are not particularly good starting batteries and can be damaged if used repeatedly in this manner. Use a dedicated starting battery. Usually, a lawnmower-size battery is good for most generator starting requirements. Anything over a 5kW or diesel generator should use something larger. Refer to the generator user manual to determine proper size.

Finally, there is still yet another installation option some have used to varying degrees of success. This is the venerable bumper mount of portable generators on travel trailers and 5th wheels. There is passionate debate on whether this is a safe idea with the argument being anything from “the generator will fly off and kill someone” to “tongue weight will be drastically reduced causing a deadly sway condition”. Properly done however, the bumper mount can be as safe as you want to make it. If you choose this route, make sure you use a qualified welder for building the generator platform, attachment points, and frame/bumper reinforcement. It is best to mount the platform to the frame rather than the bumper as the bumper is fairly thin gauge metal. Be sure you check with your RV manufacturer on whether or not the rear frame of the RV can structurally handle the additional stress as some rear walls have been known to buckle and crack depending on much weight is placed on the bumper/frame.

ModMyRV recommends these parts for this mod:

RV Generators
All Brands of RV Generators
RV Generators by Onan
RV Generators by Honda
RV Generators by Guardian (formerly Generac)

Transfer Switches
Go Power! 50 Amp Transfer Switch
Go Power! TS-30 30 Amp Automatic Transfer Switch

Exhaust Components
Onan Exhaust Accessories
Jacks Small Engines Quiet Mufflers

Fuel Tanks
Summit Racing Fuel Cells and Accessories

General Reference
How to Choose a Portable Generator for Your RV

Example Installations
Example of an Onan Installed in a 5th Wheel Forum Thread on Custom Portable Generator Installation

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18 Comments For This Mod

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  1. Bob Vaughn

    Looking at the photo of the generator mounted on the hitch of an rv I cannot imagine how much weight that adds to the hitch….I would guess that someone exceeded the max gross weight of the hitch…..I have seen a few “A” frames that came un-welded from the front cross member …..and that was just from driving on washboard roads…..

  2. ModMyRV

    That particular generator weighs around 170 lbs. And with the fuel tank and enclosure adding around 75 lbs., the total added hitch weight is around 245 lbs. That’s not all that much considering some TT’s have well over 1000 lbs. of tongue weight. If one were to do the mod in this manner, then certainly you would have to make sure you didn’t exceed any capacities, especially the trailer coupler rating.

  3. jmt

    If you don’t have a specific location for a generator and weren’t ready to add it to your hitch, wouldn’t a rear bumper install decrease the overall tongue weight? (I’m pushing 850 lbs on my tongue weight so more weight on the very back of our TT the better)

  4. ModMyRV

    Yes, you would reduce tongue weight by adding anything to the back of your towable. How much is a little complicated but there is a formula that you can plug numbers in to and it will spit out just how much tongue weight will be removed. Keep in mind that you should have at least 10% tongue weight (the more the better up to a point) to provide stability. If you are considerably over that, then adding something to the back of the TT may help to offset some of the weight. It’s no different than moving something in a front storage compartment to a compartment in the back.

  5. jmt

    Great thanks. I actually load wood, bikes, in the very back of our TT to reduce the tongue weight. I’m guessing a generator on the back would make a huge difference. Maybe some day. I’ll keep dreaming for now.

  6. Bob Vaughn

    When we started camping in the 60’s we could have made use of a generator…we dry camped all the time we would go to the national parks in the winter because they were closed but open for dry camping…there was hardly ever anybody else there….

  7. 1 Happy Camper

    For any who has mounted a generator on the back of their TT or 5th wheel, how much vibration do you experience inside the RV when the generator is running? I am considering this mod with either 2 Honda 2000s in parallel or 3000 watt generator. I just don’t want my teeth to rattle while inside the coach.

  8. ModMyRV

    Much depends on how you mount the generator. I used pliable rubber feet in between the generator and the mounting tubing going to the TT frame. My generator is a Kipor 3000i (a knock-off of the Honda EU3000) and the wheel kit mounting points on the generator just happen to work out perfectly for attaching the rubber feet. The feet are simply an elastomer rubber with 1″ studs on each side and screwed right in the wheel kit mounting holes.

    The vibration is minimal but it is there, and mostly contained to the back of the trailer where my bath and bunks are. Once you get to the front of the trailer, the vibration is almost unoticable.

    Another option is to use generator mounting springs rather than rubber feet. Most RV-specific built-in generators use this method to attach the generator to the enclosure, which is then mounted to the frame of the RV.

  9. Mark Cowperthwaite

    Does anyone know where to find a generator enclosure? My friend had a steel box built and bolted to the rear bumper of his 34′ 5th wheel.This seems like a ton of work, wondered if something could be bought at an RV place instead.

  10. Jill Kershner

    We want to put a portable kawasaki generator in the bed of our pickup. Does anyone know where we could find a locking weatherproof cover with exhaust for this purpose?

  11. Don Zinger

    I took an Onan 4000W generator that I bought used and made a mounting platform that slides into two receiver hitches that I welded to my frame at the rear of my Sunnybrook. The platform is as wide as the camper. I also mounted an 18 gallon gas tank to the platform. I used heavy gauge battery cable to connect the generator to the house batteries with a Warn Winch connector for easy hook up and removal. I used a standard 4-wire trailer harness to run the remote start circuit into the camper. My wife gave me the great idea to use trailer jacks (with the rotating wheels on the bottom) at all four corners making removal and installation a breeze! We love it - and I can have it on or off the camper in about 15 minutes.

  12. Jeremy

    This place has boxes for the honda 3000

  13. Tony

    A buddy of mine tried the GenSilencer exhaust silencer and liked it. it attached to his muffler face without welding and hung from the frame. it cut the exhaust noise. engine noise was still there but it was a lot more bearable. he could easily remove it when necessary too (storage, etc.) since it was a bolt on.

  14. harley

    My son and I took an aluminum diamond plate 5th wheel tool box and cut the bottom out of it,mounted it on 2″x2″ angle iron installed an Onan 4k , small gel cell battery and a 5 gallon fuel tank. We then cut out the end of the box and installed a fresh air grill on the other end we mounted a 30amp weather proof recepticle and a 120v duplex recep.
    This was mounted to a 2″ stinger which slides into my receiver on camper, we used a flat four wire connector to the remote start switch mounted inside camper, so you can stay inside to start/stop and never get out in the elements.
    when not in use slide the gen set out and store in garage or slide it in the hitch on my truck for a great remote portable generator.

  15. wowlites

    That sounds like a sweet set up you’ve built. Any chance you have some picture that you can share?
    Cheers Rick T.

  16. Mrs Nazario

    I like to ask you for help I just build a RV I have a kohler generator I like to take the gas from the truck tank. Not space to store one. Please if you have any diagram or parts or how I do it. Please help me. Thanks


    I would really like to purchase the generator in this Youtube video, but I’m just
    not sure if it’s the right one for me personally! Does anybody else know something about the generator?

  18. shanz3n5

    Need Info on the mod regarding portable fuel tank and connections. I have this generator installed on my toy-hauler but factory fuel tank is bad. Id like to install a portable one.
    Thank you

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