Question about Dometic Rooftop RV Air Conditioner

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I have a Puma 30DBSS travel trailer with a 30 amp service and would like to install a second rooftop a/c since the one cannot keep up with the high humidty and heat. Stand alone unit or ducted into the current ducts?

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Dometic air on a puma turns off and on

Posted on Aug 23, 2011

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As "Icemelts" has stated, unless your unit is already set-up for 2 units, it will require a lot of work to do it properly. even if you go with ceiling discharge instead of running in to the duct work, you still have to get a supply cable there for 120VAC. Although you have 30 amp service, you will not be able to run both units at same time, unless you have a generator running to power one or the other separately. Both units will draw 13-15amps when running, and up to 17-18 amps when compressor kicks in, so when you add that to a fridge that's running, as well as converter, coffee maker, toaster , or any other appliance you have to use, your main breaker will be tripping constantly, if it doesn't trip constantly with just the 2 AC units running. I'd watch for one of those portables on sale, and use it where you need it the most. Their easy to discharge out a window. Tinted windows, shade on roof would also be a little help as well, but I wouldn't go through the hassle of installing another rooftop unit when you'll only be a able to run 1 at a time. Even with a portable, you'll have to juggle power, such as making sure it's off when you need to coffee, or to use microwave etc. Run fridge and any other accessories on propane if that option is available, to reduce power needs in trailer.

Posted on Aug 01, 2010

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I'm from East Texas and me and my wife are full-time Rv'ers (since May 2010 when we both retired), so your question is an interesting one especially since we spent 2 weeks (1-15 July) in East Texas in some brutal heat/humidity.

I must say that when I bought my 5th wheel (38' Open Road) - I suspected that my AC unit (1 on the roof) would not work well in the hot Texas 'sun,' and it .... did not. But, in any event - like I mentioned - I "was not" surprised.

My idea was to stay out of the hot summers down here - which we plan to do from now on - but - because of a 'family reunion' we had promised to attend - we did - as I mentioned above - spend a couple of weeks in the heat. The best I could do was to hold the inside temp to 82-84 degrees and that was by making sure 'everything' - pressures, amps, freon charge, coils being clean' - was operating at maximum effienctly.

Like I said - we don't plan on being here (East Texas) during the brutal Texas summers in the future - but - if I was going to be - I would do the following.

#1 Fix - 'if I was not "moving" the RV and it was staying in one place and was likely to stay in that one place for a long time - I would install a 8 to 10,000 Btu window unit in my bedroom. In the winter I would probably leave it in the window (although removing it would be an option) and just 'cover' it with plastic of some sort to keep the cold out.

#2 Fix - if I was planning on 'moving' the RV in the future - and especially if I was planning on moving it 'often AND - staying in "hot weather country" - I would have a "stand alone unit" installed on my roof - right over - the bedroom. As for size I think I wouldn't put anything bigger than a 10,000 Btu unit in, and might even opt for a 8000 Btu.

The main reason I would stay away from using the existing duct in combination with the air I am adding - is that the duct system on a RV is fragile/troublesome to begin with and I would hesitate to 'add' to the load on it - or - to put all my eggs in one basket so to speak.

Again, the window unit (in the window) is the best and the cheapest option you have and if I wasn't planning on moving it - that is what I'd do. Here's a thought - since we've been in Wisconsin visiting my wife's sister (average daytime temp around 80 degrees) our AC has been 'freezing' us out - working like a charm. So.. if you 'are planning' to move and think you'll be able to stay out of the 'really hot weather' (like Texas/Oklahoma in June/July/August) - then the window unit (Fix #1) is by far the best option because when you leave you can take it out - restore your window to it's normal condition - sell the AC for a few bucks and be on your way.

Note: Since you have a 30 amp service - I would highly advise you to check with an electrician/Air Conditioning Service Tech about the "added amp draw" you will have and be sure - that your RV will handle the "extra electrical load" - any - modification you make will cause.

hope this has helped

Posted on Jul 29, 2010

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