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Enclosed generator box on truck thoughts

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It looks like I have room to construct an under-bed box big enough to hold a typical 2500- 3600 watt generator behind the rear wheels of my Volov. I want it enclosed, on a drawer so it can be rolled out and serviced. Able to run with the door closed.

Airflow is the big issue and exhaust. Something cleaver needs to be done so the generator can move in and out and still have a clear exhaust pipe path out.

Thoughts on this are appreciated. I have some ideas but need input on how one might keep the elements out of the opening where fan(s) would draw in or move air out of the box. And how to deal with the exhaust pipe from the generator.




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I made a angle iron tray on fixed wheels my door folds down to become a shelf to slide it out on. I thought about heavy drawer slides as mine is a Yamaha 6500 but when this route instead. I made the front and back solid and the inside 3/4 high, so far it has stayed dry and I open the door to run it. I use chains to support the door when its a shelf and ajust the opening to a couple of inches when in use, so people don't walk into it with there shins. With a smaller unit I might forgo the sliding rack.

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As soon as the internet is back up I will post a couple pics of what I did.

I have an onan out of a old motor home. I put it in a big aluminum tool box with vents cut out. Its designed to be in a small area. 

 I had an electrician install a breaker box with a camper plug and install 4 regular outlets on the bed and 2 inside the cab. 

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If you use an Onan "RV" type generator like the 5500 in my trailer, the cooling air is discharged underneath.  There is an expanded metal grate.  The generator housing/insulation is pretty well enclosed.  There is a high grate in the enclosure to let air in.  I now use one of those "genturi" kits to route the exhaust to roof height.  I was attending the Pacific North West Rain Festival one time. I fired the genny to make some coffee and run the furnace for a few minutes one morning. It was one of those 100% RH mornings, flat calm, light drizzle.  In 5 minutes my CO detector went off inside the trailer from the generator exhaust in the factory location, down and out to the side.  Apparently the bedroom and main room slide seals on that side are not as air tight as they look? Anyways threw the doors open and ventilated...

So the long story is your fabrication looks top notch I would think how I could route generator exhaust up to the back of truck cab somewhere and get it up in the air out of the people on the ground and under the bedroom of the trailer area...

I believe the Onan manual has installation instructions with respect to venting etc for cooling.   If you could fit a diesel like used in fancier class A motorhomes you are not adding another fuel type to manage. 

Edited by noteven
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So my thoughts on the generator box being behind the rear wheels is that even with the mud flap between, there's going to be a lot of 'wet' around there on those rain days. Maybe not enough to worry about if I keep the vents inside the frame and to the rear.

Exhausting (like all these projects, in the end) will need to be close to the box. Maybe the exhaust pipe wraps under the box and out the same side? It would be bend-ridden piece of work to take it under the frame, up to the cab, up the cab and out the top near the engine stack. I can't imagine the air resistance in that 28' run of inch tubing.

The box will be 20" W x 30" D x 24" tall. Most enclosed generators like the Honda 2000i will fit in that space. The case of the generator silences the unit and more sound padding inside the box should create a fairly quiet unit.

I need to figure on which side the generator takes in air and which side it exhausts the hot air. Not having looked closely, I'm thinking they pull from the front and hot air goes out the back, along with the exhaust pipe. My Champion 3600 w frame-type generator, sucks cool air in the back where the alternator is and this blows towards the engine. Most who mount these in RVs mount the hot air exhaust fan under the generator (through the compartment floor).

I can create an extension on the generator exhaust pipe that will slide a few inches inside a slightly larger pipe. I might even find a heat resistent gasket/o-ring to fit the junction of the pipes. Flex-pipe is not an option, I would think, due to the drawer roll out of 25". Unless that pipe made the U-turn inside the box and exited through the floor in the outside(front) of the box. Not sure how flexible that stuff is. Bit of research needed. But it would add a lot of heat to the inside of the box unless it was wrapped.

I plan on putting a 12v automotive radiator fan (small one) in the box to positive-pressure the box. Although it might be better to reverse that and suck the air out of the back (inside frame) side of the box.

Just ramblings so far.

Oh, Champion generators just announced a 220v 3600w diesel generator. Not sure it's available in the US as yet. It's the same small form factor as the inverter, enclosed generators. $1400 if I recall. Hmmmm.


Edited by trimster
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Save a bunch of pipe and make it a weed burner style exhaust or over the top of the generator to the front door with a slot in it so that the door can be opened without interfering with the exhaust.  That would make it fairly short.  Can always wrap it with exhaust tape.

24 minutes ago, trimster said:

I plan on putting a 12v automotive radiator fan (small one) in the box to positive-pressure the box. Although it might be better to reverse that and suck the air out of the back (inside frame) side of the box

Dont forget about a computer fan or 2, but you MUST provide clean combustion air or the thing will run badly with mixed air.

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Could the exhaust be mounted internal to the enclosed box, then fed into a venturi piping and divert it up and away from cab and above head level further reducing noise?

I would suspect no need to completely enclose, the sound abatement can be handled with four solid walls and the venturi.

The top and bottom of the box really should be similar to the doors over the generator doors on toy hauler campers?

Also if you route the exhaust above the trucks cab, the weight of CO 2 would tend to find ways into the cab on calm days?

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I have a 5+ yr old Champion 3600 with few hours on it. Thought about pulling it from the frame. It's 17" w X 22" long X 14" tall. It's not the newer inverter technology,  but I have rewired the output so one gets the full 30 amps thru the custom installed RV plug.

I looked at 20 gal fuel tanks to mount between the frame, higher than the geney.  Got room for that. Having 2 fuels on board is okay with me.  I could use some backup gas for the Goldwing. 

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   One thought is to mount it like front mounted generators in Motorhomes. The ones that slide out. Just have it slide out to the side. That will give a good idea how they do that. Also for the venting underneath, look at a metal panel with louvers in it. Face them to the rear.   Another thought is a bigger fuel tank.  I used my 2 1/2 gallon tank for a number of years. Then started doing more off grid stuff. Pain in the blank keeping fuel in it. Then installed a 20 plus gallon tank.


  While your are at it, maybe you should build it so a onan unit would fit.



  Just thing,    Vern in a T-shirt 

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I have two of the newer Champion Invertor/Generator's.  I have added a plastic boat fuel tank with the Johnson quick connect fuel fittings.

On the Genset, I added a vacuum fuel pump to pull fuel from the boat tank.  The instructions are on the interwebs.

Works well and runs a very long time on the tank.

I added a fuel filter inline that has a removable bowl, as the only issue I have had with the generator is trash in the needle and seat.

Oh, one other issue is valve clearance, be sure to pop off the valve cover and adjust the valves as needed once a year. Perhaps before you install it on the truck would be a good idea.

The investors are quite a bit quieter, and I did not need to enclose it in a box.

The invertor also has a remote start feature that I can start the gen set from the bunk in the truck and anywhere within my travel trailer, especially nice in in-climate weather.



Edited by Parrformance
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Bob, found the generator mounting pictures in the archives. It was a pretty hairy project. Big sucker, diesel powered, don't remember if it was a remote start, but it had it's own battery.


We needed to figure out opening in the box for it have enough CFM of air to run properly, exhaust routing was funky too to keep it away from stuff. It was a heavy SOB but it needed to come out for the most routine servicing (like changing filters - NO CAN DO THROUGH THE FRONT DOOR). So we installed small 3 inch C channels, mounted the gen on a plate and put wheels to ride in the c-channels. Note in the picture small angle pieces bolted in the end of c-channels, holding the whole thing inside the box after it is rolled in.


For servicing the little angles come out to be replaced with c-channel outriggers so that the gen can be rolled out from the box.



Everything, the diesel lines, electrical cables and harness needed to have service loops in order to be able to roll it out.



The battery and the battery box had to be mounted on the opposite side of the frame (there was no room for it on the generators side). The same size box was mounted on that side for tools.


Note the cutout in the upper left cabinet wall, that was the only way we could to the battery if we needed to deal with it.

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