Air conditioner size

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.

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.

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.

As you can see, it depends. Our 30' has a 13.5K AC unit. As shipped from the factory I would have said NO!. However, once I got in and opened up the plenum, used foil tape around all the cracks where air could go from the ducts to the attic, added 4 more "Aireoport" vents into the ductwork. The answer is now YES. With the change we went from "almost adequate" to "barely adequate".

Now ours is NOT a true 4 season trailer. If yours is a REAL 4 season trailer, with thermopane windows and very good insulation with proper ducting etc. 13.5K may be fine as delivered.

But while it will get the unit cooled down it does take time. If you have an option of a 15K or two units, I'd go for it in a heartbeat.

If ours would have had a second air prep or 15K AC option I would have gone for it.

As far as comments on short cycling. Well if that is an issue along with humidity, then a portable dehumidifier will solve that problem in a heartbeat.

A consideration not yet mentioned: a 13.5K should have no problem starting up and running with a single 2000w genset; I believe that the 15K will need a bigger genset to start up and keep running on 100+ deg days. I found that I need to run both of my Honda eu2000s linked together if I wish to run my 15K A/C unit.

marcsbigfoot20b27 wrote:

Bob Landry wrote:

Dick_B wrote:
What makes the answer even more complicated is that one can have too LARGE an a/c because if it cools too fast it doesn't dry the air and you end up with cool clammy air! I vote for 13.5.
We also find an oscillating fan helpful to move the cool air around.

Given the poor insulation of all trailers, the 13.5 is inadequate in all but the smallest trailer. It's possible in theory to get the space so cold that the AC short cycles, but you are never going to see that in a trailer. More is always better and in Nevada, you are going to need every BTU of cooling that you can get, and no, it doesn't matter if it's "dry heat", it's still heat and has to be removed from the trailer for you to be comfortable.With the 15KBTU AC being about a $150 option, that's a no brainer, you'll be comfortable and it will help the resale value of the trailer.

I disagree. My 27 ft Bigfoot has excellent insulation and the 13.5 does awesome. Of course it is a true four season trailer with thermo pane windows, awnings for all windows, etc. BTW, I live in Phoenix where it is 115 degrees in the summer. And dry heat DOES matter! Removing the moisture from the air takes energy, which equals less cooling.
So it all depends on the TT setup.

Disagree if you like.. Your prerogative..

If you have a true 4 season trailer, congratulations. We are all happy for you. The brunt of production trailers, in spite of the ad hype about Polar and Arctic Packages, and inflated published insulation R values, are 3 season trailers at best, with poor insulation, single pane windows, and poorly installed plenums and duct work, and they need al the help they can get, even after fixing the manufacturers shortcomings. Also, my comment about it being unlikely that the AC is going to overcool and short cycle still stands. It's not going to happen on the average production trailer, and the $150 difference between the two units, assuming there is only going to be one, still makes it a good value.

More is always better and in Nevada, you are going to need every BTU of cooling that you can get, and no, it doesn't matter if it's "dry heat

The OP lives in northern Nevada a few miles from Lake Tahoe at about 5000 feet elevation, not Vegas. The climate and temps are totally different from southern Nevada.

Bob Landry wrote:

Dick_B wrote:
What makes the answer even more complicated is that one can have too LARGE an a/c because if it cools too fast it doesn't dry the air and you end up with cool clammy air! I vote for 13.5.
We also find an oscillating fan helpful to move the cool air around.

Given the poor insulation of all trailers, the 13.5 is inadequate in all but the smallest trailer. It's possible in theory to get the space so cold that the AC short cycles, but you are never going to see that in a trailer. More is always better and in Nevada, you are going to need every BTU of cooling that you can get, and no, it doesn't matter if it's "dry heat", it's still heat and has to be removed from the trailer for you to be comfortable.With the 15KBTU AC being about a $150 option, that's a no brainer, you'll be comfortable and it will help the resale value of the trailer.

I disagree. My 27 ft Bigfoot has excellent insulation and the 13.5 does awesome. Of course it is a true four season trailer with thermo pane windows, awnings for all windows, etc. BTW, I live in Phoenix where it is 115 degrees in the summer. And dry heat DOES matter! Removing the moisture from the air takes energy, which equals less cooling.
So it all depends on the TT setup.

Since the OP is in Nevada, I vote for the 15K unless he is going to be camping elsewhere.

Not much shade or Humidity there so every BTU will help.

Our HTT had a 13.5 and never had a problem keeping cool, even with the insulation issues with a hybrid, until.....we went to Vicksburg, MS and the temps were right at 100 with nearly that in humidity. We could SEE a shade tree, but that was about it and we couldn't get it cooler than 85 degrees. All of our usual campgrounds have nice shade. Made a Walmart run for an oscillating fan and all it did for us was to move the 85 degree temp around inside. As soon as the sun went down, it got comfortable pretty quickly. Forward several years to changing to our 26' TT and as it happened, it has a 15K. It is much easier to cool, although we've not been in places without trees. You really need to consider the shade factor and how miserably hot it is. IMHO, if you are able to work a change from the 13.5 to a 15K, I think you'd be happier.