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 > Question-Can I use my roof mounted a/c in my stationary rv

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North Hampton Beach, New Hampshire

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Posted: 07/09/18 10:57am Link  |  Quote  |  Print  |  Notify Moderator

While I'm new to RV.NET, I'm not new to forums in general.
I have a question regarding whether or not,it would be a safety issue to use my rooftop mounted (working) a/c unit to cool my '87 Franklin 35 ft., STATIONARY travel trailer, that has had a wood framed, pitched metal roof added 10 plus years ago.
There is also at the opposite end of the roof, an attic exhaust fan (currently not hooked up to power.).
Can I/should I attempt to use this now enclosed a/c unit, only if I use the exhaust fan at the same time, to avoid overheating..., or should I just scrap the whole idea of using the roof top a/c, altogether..?
I have talked to a licensed electrician, who was not sure if it was legal (in the state of NH) or not, but declined, because he did not want to risk his license.
Any thoughts or advice would be GREATLY appreciated.
Thank you.


South Louisiana

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Posted: 07/09/18 11:01am Link  |  Quote  |  Print  |  Notify Moderator

Run the AC and exhaust fan at the same time.


Verde Valley

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Posted: 07/09/18 11:04am Link  |  Quote  |  Print  |  Notify Moderator

Run the trailer A/C Unit.....if it trips THEN worry about hooking up exhaust fan power and run both

Is it time for your medication or mine?

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Over There

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Posted: 07/09/18 11:24am Link  |  Quote  |  Print  |  Notify Moderator

I kind of don't understand your situation. An RV air conditioner should work in any type of room or building. The air conditioner has an air intake from inside and then it circulates the air inside the conditioner, passes though the condensing coils, and spits cold air out the other side. I don't see where having any kind of exhaust fan in the building, on the opposite side of the building would make any difference. The air conditioner is designed to run and cool in any enclosed space.

Now, in order to circulate the air in the building (or completely sealed up camper), a circulating fan would help... you know, a simple floor or desk fan to push the air to the other side of the room or down a hall or something. Thus ... some manufacturers use duct work in the roof of RV's for the cold air to make a passage to each end of the camper. But a center blast air conditioner will simply blast the air straight down. You may want a separate fan to circulate the cold air in the room.

But needing an exhaust in the building is not needed at all.

The only thing you'll want to watch for, is to make sure the air conditioner can sit somewhat flat and somewhat level. I've seen RV air conditioners on 5ers where they are located on the roof between the low spot and the high spot on the over hang, at an angle. It looks weird, but I suppose they work OK. Still, if I were doing this, I'd want it as level as possible.

Other than circulation in a room, an RV air conditioner works pretty much like a house window air conditioner. Hot air in, cold air out. Do you need an exhaust to run a window air conditioner?

I re-read your post. Are you saying the trailer air conditioner is located between the roof of your trailer and an add-on roof above the trailer? So if running, the air conditioner now way to cool the air conditioner components themselves, thus building up heat and eventually burning something out ... no surround air circulation? If so, then yes, run the exhaust fan. I think I get it.


Oliver Springs TN

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Posted: 07/09/18 11:44am Link  |  Quote  |  Print  |  Notify Moderator

I think I half way understand your question. Your roof A/C is intended to be open to the outside air to remove heat. Running the roof air in an enclosed "attic" will build up heat in the "attic". The heat needs someplace to go. You need to ventilate the "attic".

Chris Bryant

Arden, North Carolina

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Posted: 07/09/18 12:19pm Link  |  Quote  |  Print  |  Notify Moderator

Can you actually get to the unit? If the roofover is big enough to get in there, I would try it. If it isn't, I wouldn't trust it.

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Posted: 07/09/18 12:29pm Link  |  Quote  |  Print  |  Notify Moderator

A picture of what you are talking about would be a great help.
But, If your AC is inside an enclosure that contains the rest of the trailer, understand that a similar amount of heat will be generated in the roof enclosure as compared to the cool air being placed inside the trailer.
So long as you can give that warmer air a means of escape, with outside ambient air able to replace it you should be fine.

Also understand that the rooftop AC will generate condensate (water) which will drain toward the sides or whatever low point is available, just like you see drain from a window AC. You must give that somewhere to go.


Pisgah Forest, NC

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Posted: 07/09/18 12:38pm Link  |  Quote  |  Print  |  Notify Moderator

If there is any way for air to circulate from outside it would work, the less air the less efficient it will be. If there is no outside air then I don't know where the exhaust fan will get air from, if there is a grate at the other end I would say your best bet is to hook up the fan for better efficiency. Don't see how it could be against the law but who knows.


No paticular place.

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Posted: 07/09/18 12:48pm Link  |  Quote  |  Print  |  Notify Moderator

A big ole...depends.

How much space and airflow is there in the attic area?

A ventilation fan would certainly help but again without details of the space hard to say if it will be enough.

If its a small poorly ventilated space, temps could easily push 130F in the attic. On really hot days it can go even higher. The Air/con unit at best will be severely hampered in it's cooling ability in those conditions. Plus it will be pumping more heat into that space. You could easily push it up north of 150F.

Those kinds of temps could be really hard on the air/con unit.

PS: Did an experiment several years back looking at LED traffic signals. We put a temperature probe inside the head in direct sunlight. It got up to 160F and the LED unit generates almost no heat. Black shingles would be far worse than a yellow housing for absorbing heat.

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John Wayne

Long Beach, Ca

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Posted: 07/09/18 12:55pm Link  |  Quote  |  Print  |  Notify Moderator

And don't forget if running the RV unit in the attic you will need some way to drain off the water that the RV A/C will produce.

John & Carol Life members
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