Air conditioner size

CavemanCharlie wrote:
It flows a lot of air. I have a clean filter and on this unit I can look up into it with the filter removed and see the evaporator . Maybe my thermostat that I'm sticking right into the outlet of the AC is not very accurate. And, if I recall it took a while to get down to that temp. Started out more like 40 I think. Can't try it now. it's only 25 outside here. lol

Boy, I can't see how you ever expect to get a poorly insulated, drafty, RV cool inside by putting out 60 degree air.

Believe it or not, even in a central AC unit in a stick n' brick, the temperature "split" between room air and the air handler discharge plenum is only around 20 degrees or so. No AC expert but when we replaced our home heat pump 4 years ago, the technician showed me the figures with his electronic thermometers when the installation was completed as part of the startup and customer acceptance of the job.

My dealer told me the difference between the 13.5 and 15.5 is the fan motor. Maybe?

Mine came with a 15k. It did fine in the shade but without shade it struggled in the NC heat. We stay at the beach a good part of the summer and it would get up to about 84 in the camper. It did feel cooler than that though. I covered the windows and skylights which helped but it was no fun being in a cave. Couldn't look out of the window, always dark with little natural light. And you didn't dare cook in the camper during the day because it would heat the camper up and wouldn't really cool down until the sun went down. So I added a second 15k A/C. Best thing that I have done to that camper. Now I am not afraid to cook or open the door during the heat of the day. A wise old man once told me that you can finish with to much. Sorry for the long post.

We ordered the 15K on our new 35 ft trailer. Our 25 ft had the 13.5K and stuggled when temps got over 100. The cost difference is not much, about 150 bucks to get the 15K on our model. Go 15K IMO.

If you camp in this kind of heat regularly, I'd push for a 15K a/c. We camp in GA and FL, and the 13.5K unit just can't keep up when it gets hot. We used to have a camper about the size you're looking at, so been there, done that.

jrichard wrote:


Having said that, I wouldn't pass on a trailer just because it had a 13.5k unit.

At one time I would have said that, but having spent a summer in the Texas heat in a Jayco with a 13.5 AC, my thoughts about that have done a 180. It would be a deal breaker for me now, simply because of seeing how hard it is to cool a trailer, even after the manufacturing installation and duct problems have been fixed.

I've had similar trailers with both sizes. If given a choice, going with 15k is a no brainer...typically around a $150 upcharge ordering new. A little extra money and a little extra cooling ability.

Having said that, I wouldn't pass on a trailer just because it had a 13.5k unit.

On my brothers unit we thought maybe it was plugged. We couldn't see the evaporator from inside the RV. I went on the roof and removed the cover. (Boy was that cover cheap and flimsily compared to what they used to be) Then I found I still could not access the evaporator because the whole tin around the evaporator was pop riveted, spot welded, or had bent over edges so that there was no way to get to it. Then after blowing out the condenser (which I could get to) we turned it on with me still on the roof. On my old unit the fan draws cool air from the outside environment in threw slits on the sides of the cover and blows air threw the condenser. (toward the back of the TT)

On his unit it draws air threw (or you could say it sucks air threw) the condenser, then tries to exhaust the hot air through the slits on the side of the cover. ??? WTHeck ??? This also means it blowing hot air right at the compressor which is the hottest working part of the unit. I couldn't believe my eyes. No wonder the darned thing works so bad. Stupidest engineering I've ever seen.

You suppose when it was built someone put the fan blades on backwards? I can't believe the could build anything that dumb.

It flows a lot of air. I have a clean filter and on this unit I can look up into it with the filter removed and see the evaporator . Maybe my thermostat that I'm sticking right into the outlet of the AC is not very accurate. And, if I recall it took a while to get down to that temp. Started out more like 40 I think. Can't try it now. it's only 25 outside here. lol

Boy, I can't see how you ever expect to get a poorly insulated, drafty, RV cool inside by putting out 60 degree air.

CavemanCharlie wrote:

Bob Landry wrote:

CavemanCharlie wrote:
I have a old 20 foot TT with a discontinued Emmerson roof mount AC unit. I have no idea of the size but, it puts out 35 degree cold air on a 85 degree day. My brother has a 3 year old 5th wheel and his "Brisk Air " roof mount unit only puts out 60 degree air on a 85 degree day. I say go with the bigger unit because the new roof mount AC units are junk and don't put out decent cold air.

Between 56 & 60 degrees output temp is what a R22 unit will do. 35 degree air indicates an air restriction either dirty return filter or a blockage or restriction somewhere in the ductwork and at that temperature, the evaporator temp is below freezing and if it's running in a humid environment, it will ice up rather quickly.

No, it works quite well. There is no restriction and no ice up problems. Maybe it's not R22 ? I know my car AC also puts out 35 degree air but, of course that is not R22. It used to be R12 but, was converted to R 134a some years ago.

If it works good enough for you, that's good enough for me. I sell, install, and service AC equipment and I'm just saying that on a properly charged unit with clean filters and no restrictions, 35 degree discharge temperature has the evaporator temperature below freezing and it should be icing. Why it isn't, I would have no way of knowing without looking at the whole system. Hold your hand in front of the discharge and slowly back away from it and see if you still feel air coming out. A symptom of restricted air flow is that it will be very cold right at the grill, but you feel little air movement even a short distance from the vent. I'm glad it's working to your satisfaction.