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Old 08-19-2011, 08:31 AM   #1
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Larger A/C Help

Hi All,
Does anyone make an roof a/c with ducts that is larger than 15,000 BTU's?

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Old 08-19-2011, 09:13 AM   #2
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NO. You have to add another unit.


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Old 08-19-2011, 02:06 PM   #3
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What's your issue, Dave? Has it worked OK up until now; suddenly started to under-perform? You might try blowing-out your fins topside if they are clogged.
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Old 08-20-2011, 07:16 AM   #4
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Larger A/C

When it is over 90 the two of them on high will not keep the coach cooled.
I am not sure what size they are, but if they are 13000 btu units another 2000 btu's is not going to do the job.
I have tried cleaning and had the dealer service the units. They are just not big enough. Typical coach builders cheap!!!!!!!!!!!!!!!!!!!
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Old 08-20-2011, 12:23 PM   #5
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15k BTU is about the maximum for RVs because it represents about the maximum practical load for a 115-volt circuit (even if your rig has 50-amp 240-volt service it is split to two 120-volts legs at the panel and usually no full 240-volt service is available for internal electrical loads.) It could be wired otherwise and thus provide 240 volts to a much more powerful A/C unit, but that would mean that your A/C would not be functional at a campground without 50-amp service. Most owners would find unacceptable so it's generally not wired that way.
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Old 08-20-2011, 01:48 PM   #6
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I just got baqck from Las Vegas.....109 degrees!

The two 15K's kept the inside to a chilly 79 degrees...

I was amazed....
Michael (Home base Northern CO)
USED TO HAVE; 03 Alpine 40MDTS Now RVless
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Old 08-21-2011, 08:05 AM   #7
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2 x 15,000 BTUs should be enough for the square footage. If it was a house the a/c experts would recommend about 5000 btus for a 400 sq ft space. The problem is that RVs are poorly insualted vs a fixed dwelling and just aboyt every surface is an extyerior wall that heats up. They are are lots of windows, plastic skylights in the roof, etc. etc.

You will probably get better results by working on how the RV gains heat. Put "pillow' insulation in the skylights, reflective tint on windows (or foil backing), reflective sun shield in the windshield, window awnings to help sahe the, use the patio awning to keep sun off one side, and so on.
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Old 08-21-2011, 02:13 PM   #8
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We are finding that the mostly black color and huge windshield of our coach makes it darn hard to cool in 90+ degree heat.
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Old 08-21-2011, 04:26 PM   #9
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Get some external shades, it will keep the heat out and put less pressure on your air conditioners.
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Old 08-22-2011, 03:47 AM   #10
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Gary' Brinck's comment is the bottom line. Instead of adding more capacity (which simply isn't practical), you need to reduce heat conduction by insulating your rig in creative ways. Windows and vents are the biggest culprits but cabinets can also be a weak spot. We added a sheet of one-inch blue board (foam insulation) to the back of our wardrobe and found that the bedroom stayed much cooler. We're going to do the same to the back of our living room cabinets. The other advantage of tightening up is less condensation in cold weather. In any case, find out where heat is getting in to your RV and do anything to slow it down. After that, you'll find that two roof ACs should keep you pretty cool.

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Old 08-24-2011, 02:36 PM   #11
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Target the 3 types of heat transfer conduction, convection and radiation:

Agree with the after-market insulation ideas. Especially the backs of wall cabinets [if only solely for saving contents from excessive heat]. A dead-air space is the best insulator, such as bead board insulation.Foam padding is next in line. Bubble wrap also but it has a short life-span. Just some obvious ideas...for the first "two" sources of heat gain.

But, for the third: Radiation,
I had Great success in adding batt insulation into the front cap, just behind my TV and stereo cabinetry. Huge improvement occurred when I added a foil radiant barrier behind batts[nearest to the cabin side].
Many people do not seem to understand unseen radiant heat ( solar infrared energy) often causes just as much heat gain as the other two transfer methods.

Many new homes have foil-faced attic insulation at the rafter level; thus giving the attic space a cooler effect than if foil was placed at the ceiling level.

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