Ventilated Generator Compartment??

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John Doe

Jan 7, 2007
Greetings to all in this new year! I am new to this forum, so I'm not sure how often topics are updated. I currently own a 1995 32' El Dorado Class C motorhome built by Honorbuilt Industries (no longer in existence). My generator compartment is on the driver's side, first compartment on that side of the coach. The area in which I travel gets to be very, very unpleasant in the summer with low 100's in temperature. Dash a.c is wonderful, but I would love to be able to run my 15,000 btu roof a.c while driving to cool the whole coach. I am well aware of the fire hazards presented by running the generator while underway, and after seeing the destruction of many other rigs, I am afraid to try it. My question is this: Is there a way to ventilate the compartment to keep the generator cool and still run the roof a.c??? Replies would be greatly appreciated!


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It's common to run the generator for the roof A/C while traveling in hot temperatures.  The generator compartment should be designed to supply adequate ventilation with the access door closed, and should ventilate even better while moving.  Is there something in your documentation that indicates the generator can't be run while moving?
There's nothing in the documentation that I have so far seen. I've heard many horror stories from mechanics, and other rv owners that running the gen set while driving caused a massive fire from inadequate ventilation. I have since then been afraid to test out the theory, because my rig is well, my baby. But you think that the mesh/chicken wire screening on the compartment door will provide sufficient air movement? I've had the thought of purchasing side vents from West Marine and attaching them to the compartment door. What do you think?
You need to tell us the make and model of generator.  My Onan 2800 has forced air cooling...  It takes in air on one end of it's enclosure and dumps it out the bottom where it partly cools the exhaust.  All it needs for cooling is a source of air. To see if yours is similar, run the generator and use your hands to see if a large amount of air is being expelled from the bottom.
I have never heard of a fire caused by running a generator while traveling, but that doesn't mean it hasn't happened.  It's just very improbable as this is a common practice.  In the photo, your generator compartment door has a large vent at the top, so it's obviously meant to be used while closed.  If anything, it should get better ventilation while in motion than while parked.
Karl said:
Looking at the picture, it appears that the generator is mounted at a pretty severe angle. Should it be that way? looks like it might have some lubrication issues. Just curious ???

Karl, I believe that's just the way an Onan is structured. Notice the oil inlet area is horizontal. But what do I know -- I'm a programmer. :)
John Doe said:
My question is this: Is there a way to ventilate the compartment to keep the generator cool and still run the roof a.c??? Replies would be greatly appreciated!

Hi John Doe:

I worked with a Genset guy in Sacramento -- supposedly the best in the West installing a Generac 3600 in the bed of my pickup when pulling a trailer then a 5th wheel. Ventilation of a genset was stressed to the nth degree because it generates tons of heat as well as electric power. A hole was cut in the truck bed under the genset to let the exhaust air out the bottom of the unit.

Notice the ventilation screen on the door is at the top of the door. This is because the genset is sucking air in from the top of the unit. Then I notice that I can see the ground through the door. That is because the air sucked in from the top is expelled out the bottom. That displays to me that your genset is most likely installed properly and has the right amount of ventilation already. If that hot air cannot be expelled out the bottom -- that's when a unit is in trouble -- as that air can get extremely hot.

As far as room around the unit, your instruction manual should tell you the required inches clearance required to the left, right, top and rear side of the unit -- and that should be easy to verify. However, unless that unit was originally smaller and replaced -- am reasonably sure the manufacturer complied with the installation specs. You might want to try turning it on, turn on the Air -- then drive around the block a few times. Would imagine the unit will run cooler while underway -- as Ned points out.

A little sidle here. The fellow that cut the hold in my truck bed wrapped the cut out to give to me -- if I ever wanted to put it back. Anyway, he wrote on the wrapping, "Bob's bed pan".  :)

That installation angle is typical of a class C.  My old Tioga looked the same way. 

I, too, thought it may be about ready to fall out the bottom, but when I  looked  at the mounting points it was clearly meant to mount that way. 

I would install a temp Gauge on the motor and run the Gauge to the cab then you can check it while traveling. A cheap peace of mind.
Thanks to everyone for your great advice. I've already tested out the generator to make sure that everything ran ok. Looking forward to next summer!!!!!
John Doe said:
My question is this: Is there a way to ventilate the compartment to keep the generator cool and still run the roof a.c??? Replies would be greatly appreciated!

I had that very same generator in my previous RV and ran it all the time on road with roof airs going ( nine years and 65000 miles). I was in hottest areas of Southwest and hot steamy Midwest and never had a problem. I serviced it myself and the my compartment looked tighter than in your photo.

In fact, my dash air went out and I never had it repaired for about the last four years we had this RV. I did not worry as we always preferred roof airs.

That is typical installation in most RVs of that time with Emerald Onan.

That's good to hear. I was under the assumption that perhaps since the generator looked so tight in the compartment, that not enough ventilation would be able to pass through freely while on the road. The genset runs great when stationary, so I'm sure that it'll do the same while on the road, if not even better. Now I just need to fork up the money for an in-motion satellite system to run on the generator  :)

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