How many btu's for a basement a/c?

[HB of CJ]

Excellent posts everyone.  Thank you.  If we ever do the Crown Super Coach Bus Conversion, (ex-schoolie with NO real luggage bays per say) we will really look hard at finding some place/space to mount the two (2) basement airs.

However, all the prior planning came to the same conclusions---there is just no room anywhere under the floor for all the stuff needed, plus finding space for the actual duct work.  Sosss, that leaves just the rooftop warts.  HB of CJ

[Rick Brown]

I've got a Duo-Therm by Dometic dual compressor basement ac; 27,000 btu total.  It has been unreliable and a pain in the patootie to pull for repair (it's broken at this moment).  If I really needed air conditioning I would look closely at replacing it with a pair of garden variety household window units mounted in the space now occupied by the Dometic.
-RickBrown in Reno, NV

[JohnEd]

Something to consider:  the roof tops mount sitting on top of a foam cushion.  I thought at first that it was a vibration/sound insulation AS WELL as a waterproof seal.  There is no sound absorbing quality to the install due to the fastening screws going through the roof and attaching directly to the AC unit.  Any body have any ideas on how to isolate the AC unit from the noise amplifying METAL ROOF?

Thanks,

John

[TomC]

John-I have three Coleman 13,500 roof tops and with the 2.25" of sprayed foam insulation, you don't even know when the compressors kick in, except for a quick dip in the generator.  The noisiest part of Colemans is the interior fan since it is only two speeds-like medium and high.  Ducted roof tops will be quieter.  I bought my Colemans in 1994 and have had zero problems with them, except to replace one of the outside shrouds.  Good Luck, TomC

[JohnEd]

TomC,

Thanks for that.  I guess that that is just one more reason to go with foam.  I read a post long ago by a Knut that had just had his interior foamed.  He was overjoyed at his QUIET bus.  He said he could not even hear the engine run anymore and had to look at his tach.  An overstatement, no doubt, but a point well made.  If it also has the effect of quieting the roof tops.....great bonus and another option for AC.  My RTs are set on that sponge seal and my roof is as follows: 3/8 plywood, 3 1/2 foam board, aluminum sheet, 1/4 ply, 1 1/2 foam board, 1/4 ply.  I can hear the compressor a little due to the mounting bolts connecting the interior most layer of my roof directly to the AC unit frame as they all do.  The real noise is coming from the air flow through that restrictive interior shroud/defuser and that is considerable, to me anyway.  I suspect that all these AC units are not created equal and some must be quieter than others.  I agree with you about ducts as I have been in a few bus type coaches with that feature and I couldn't hear the rush of air or the compressor either one. Really nice but I have been told that ducting eats up a lot of the BTU ability of the RT units.  I have never heard a number associated with that inefficiency, however.

Thanks for your comment,

John