AC vs Desert Heat!!

Steve Heywood · 05-26-2005, 05:37 PM

My 30' Excella is currently sitting in my mother-in law's driveway in Phoenix (about 103 degrees). My 13,500 btu Dometic AC is running flat out and can only hold the interior temperature at 88 degrees in the mid-day heat.

Does this sound about right or is my AC unit in need of some TLC??

wkerfoot · 05-26-2005, 05:42 PM

Quote:

Originally Posted by Steve Heywood

My 30' Excella is currently sitting in my mother-in law's driveway in Phoenix (about 103 degrees). My 13,500 btu Dometic AC is running flat out and can only hold the interior temperature at 88 degrees in the mid-day heat.

Does this sound about right or is my AC unit in need of some TLC??

Check the air temperature coming out of the A/C unit, I believe that it should be in the low 30's, if not your unit needs TLC.

Bill

Safari Tim · 05-26-2005, 05:43 PM

Steve,

That's probably about right. I have a brand new A/C just like yours that I installed on my 23'. In 100+ weather w/o shade I get about 80 degrees.

You trailer is quite a bit larger than mine so I'd bet it's doing the best it can.

Time to splerge for one of those 15K btu's? ;-)

74Argosy24MH · 05-26-2005, 05:51 PM

AC will only drop the air temperature 25-30º coming out of the coils. Check it there and see what you have. Cleaning the coils sometimes helps but it is probably doing the best it can as Safari Tim said.

John

Inland RV Center, In · 05-26-2005, 06:29 PM

Dash AC's are very different from roof AC's.

A dash AC can put out air sometimes as much as 30-35 degrees below ambient.

A roof AC, if working correctly, should ideally put out air at 15 to 20 degrees below the internal temperature of the coach.

When out in the desert, it is wise to turn the AC on early in the morning and set the thermostat a couple of degrees or so cooler than you want it. When the afternoon heat arrives, the AC should reasonably keep you comfortable.

However, in 100 degree plus sun, the heat load generated on the shell will eventually be transfered to the interior. Therefore if you allow the AC to get a head start then usually the comfort level will still be OK.

Keep in mind, the old 13,500 BTU AC's in a large Airstream trailer, cannot keep up with the heat load from the hot sun.

Likewise, although somewhat better, a 15000 BTU AC will still not cycle off when the ambient temperature exceeds 100 degrees.

Some Airstream owners have the top painted white, which helps considerably.

An absolute DO NOT is to spray the roof of the coach with a continuous flow of water. To do so, will very quickly cause the roof to have a couple of hundred holes in it, each hole being a water leak.

We had to replace a roof sheet for a customer that installed a window unit in an old trailer, and then had the roof continuously sprayed with water. After a few weeks, he called and said all of a sudden "his roof leaks".

Extending a patio and a road side full length window awning, helps to considerably reduce the heat load. A rear window awning and a front window rockguard, also helps.

Air conditioners all have their limits in terms of BTU. If the interior heats up to the point of being uncomfortable, perhaps the AC needs servicing. But if the input to output temperature (at the AC) is between 15 and 20 degrees, then that AC is doing all it can.

Andy

Steve Heywood · 05-26-2005, 06:42 PM

I just checked and with an outside temperature of about 100 degrees and an interior temperature of 91 degrees (I set the thermostat to 90 to give the AC unit a chance to run at less than 100 %) my AC unit is pumping out 62 degree air.

Sounds like it is doing all it can do given the conditions.

driftwood · 05-26-2005, 07:05 PM

Time to get a swamp cooler!

Steve Heywood · 05-26-2005, 10:58 PM

Quote:

Originally Posted by driftwood

Time to get a swamp cooler!

You live in FL and you even know what a swamp cooler is?

Actually I have my eye on adding a evap (swamp) cooler to my trailer. I like the fact that I would have a cooling device that doesn't need shore power or a generator. The only problem I see is the purchase price (I can buy another AC cheaper) and the water supply line.

warbler5 · 05-26-2005, 11:44 PM

Quote:

Originally Posted by Inland RV Center, In

When out in the desert, it is wise to turn the AC on early in the morning and set the thermostat a couple of degrees or so cooler than you want it. When the afternoon heat arrives, the AC should reasonably keep you comfortable.

However, in 100 degree plus sun, the heat load generated on the shell will eventually be transfered to the interior. Therefore if you allow the AC to get a head start then usually the comfort level will still be OK.

Extending a patio and a road side full length window awning, helps to considerably reduce the heat load. A rear window awning and a front window rockguard, also helps.

Andy

Right again, Andy! We spent 10 days in the southern California desert (Anza-Borrego Desert State Park) during April, and it was our first real "test" of the AC in our 2004 AS Classic. We were parked in full sun during the day, but the shade covered us by 6:00pm. The first day we turned it on, it was already hot, during the late afternoon....the AC never did catch up! During subsequent days, we turned the AC on in the morning and left it on, then extended all of our awnings....what a difference covering that glass made! Admittedly, there is a BIG difference between the low 90's and the low 100's, but you get the idea. The next time we make that trip, we intend to pick up those square, furry insulators to stuff up into the skylights....probably useful during winter camping, as well.

btw Steve....the weather at home (Rocklin) has been in the 90's the past few days!

Cheers, Dee

Tinsel Loaf · 05-27-2005, 12:14 AM

Putting reflective aluminum bubble insulation in all the windows, skylights and rolling out the awnings and running the ac all day will keep the interior liveable. I think the darkened interior also gives the feeling of being cooler. Oh, and a cool drink helps.

driftwood · 05-27-2005, 07:36 AM

Quote:

Originally posted by Steve Heywood
You live in FL and you even know what a swamp cooler is?

Mr. Heywood,

Well, I get around - even lived in Palm Spring, CA for a few years.

Anyway, Lazy Days used to install a swamp cooler in their units years ago.

Have you seen this? http://www.turbokool.com/

You can even go solar!

Over59 · 05-27-2005, 07:58 AM

Do these swamp coolers work when it's hot and humid or only for "dry" heat.

**jcanavera** · 05-27-2005, 09:35 AM

Quote:

Originally Posted by Steve Heywood

My 30' Excella is currently sitting in my mother-in law's driveway in Phoenix (about 103 degrees). My 13,500 btu Dometic AC is running flat out and can only hold the interior temperature at 88 degrees in the mid-day heat.

Does this sound about right or is my AC unit in need of some TLC??

Based on the performance of my 13.5 Penguin in my 27' '01 Safari, you are doing as good as you can. According to my correspondance with Dometic if the air temp drop from input to output is between 18-25 degrees, your unit is doing the best it can. In your case your trailer is 3 feet longer than mine was. I could only hold 85 on a 100 degree day in full sun. That's why I ordered the optional 15K Penguin for my 30' Classic.

You just have too much heat gain and volume for that unit too handle. Airstream had known for some time that those 13.5K units were marginal under extreme conditions. I'm sure they had some input to Dometic in the development of that 15K unit.

Jack

Rivetedude · 05-27-2005, 09:44 AM

Quote:

Originally Posted by Tinsel Loaf

Oh, and a cool drink helps.

Yes...Miller Genuine Draft works for me. Heck, I sit OUTside and drink it and that feels pretty good too!

Ben