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85MH325 · 06-25-2003, 10:06 AM

Here's a new one for us... our 34' TT has a single A/C unit mounted mid-ships. It's working fine, entirely up to its rated output. The problem is that it's not getting to the bedroom!

It was 97 degrees here yesterday, and the bedroom was still toasty at 11PM last night!

Other than putting an electric fan on the floor pointed toward the bedroom, anyone got any ideas how to improve the A/C circulation to the rear?

All of my other trailers were short enough that it wasn't a problem. The motorhome had two roof airs, so it wasn't a problem either.

We're sweltering and my wife's getting cranky!!!

Help!!!

Roger

Silvertwinkie · 06-25-2003, 10:11 AM

Well, Jack and I were talking about some of the units getting an underpowered A/C unit. I think the 13+k BTU units are best for anything longer than 19'. I think the standard model on some of the smaller rigs is 11+k BTUs I have noticed that on a fair number of the larger Airstreams, they have two units.

Jack also had some success with getting some door seals adjusted at the factory.

Just a few off the top thoughts.

Eric

RoadKingMoe · 06-25-2003, 11:08 AM

I don't have an answer for you, Roger... just some questions since we've been concerned with how well the heat pump/AC will do in really hot weather.

How hot does the living room get during a 97 degree day?

How hot is ambient temperature at night, and how hot is the bedroom getting?

I have heard of someone installing tiny computer muffin fans between the upper door support and ceiling to move some air to the back, and we've talked about sleeping on the couch if the bedroom gets hot... rather than buying a second AC.

john hd · 06-25-2003, 11:56 AM

roger,

run out to wally world and get a little fan, my trailer has the same problem. due to the bulkheads for the doors. they obstruct air flow.

set it up so that you blow air back to the front of the trailer. it really works!

all you have to do is get the warm air in the back up to the front. i set my fan on the nightstand and point it to the front.

good luck with the better half, mine does not handle being hot either!

john

wb13798 · 06-25-2003, 04:46 PM

get another ac installed problem solved. lol
al

Chas · 06-25-2003, 05:22 PM

For what it's worth,

I had a similar problem on my 27 footer. The rear a/c outlet was relatively close to the rear bedroom but the airflow was obstructed by the folding door bulkhead. I did a temporary fix by using a piece of cardboard and directing the air up and over the bulkhead. It is still in place, thought about getting some fancier cardboard and making it permanent

I am not sure if it would work on your 34' unit, that is one huge unit to cool down.

Chas

drboyd · 06-25-2003, 05:51 PM

Well, you have two basic alternatives: Use the existing unit "smarter" or add another one. Being smarter will be cheaper, I promise.

Directing the airflow to the back of the coach will obviously help a bunch - whether you use ducting, cardboard or a fan. Whatever works for you. Don't forget - the more apparent effort you put into it, the more the spousal unit will appreciate it!

The next subset of the "smarter" alternative is to reduce the heat load coming into the coach. Does the bedroom window face west? Put a shade over it! Matter of fact, shading any sun-struck windows will make a big difference. for a bigger difference, park under some monster tree for shading the whole coach.

Pahaska · 06-25-2003, 05:58 PM

On my old Scamp, there was no ventilation in the bathroom and it got unliveable in Texas summer heat. I ran a duct (actually a PVC pipe) along the ceiling into an adjacent cabinet and then a flex duct through the cabinet forward into the bathroom. The pipe simply projected into a hole I cut into the inner AC shroud and into the cool air section. On the bathroom end, I used an air vent outlet that I found in a store that sold van and pickup parts. I covered the duct with material that complemented the interior liner.

I think a larger version of the same idea would work in most Airstreams that I have seen. There are all sorts of things that could be used to form a suitable duct. Depending on the AC maker, the duct may just have to go through the outer wall of the inner shroud or may have to go through an inner wall as well to get to cool air.

I could do something very similar in the International, but I am working on a 130 watt Peltier effevt heater/cooler for the bathroom instead.

drboyd · 06-25-2003, 06:08 PM

...that sounds good, although I can't quite visualize it.

On the Peltier heater/cooler, don't forget that the unit is effectively a heat pump. If you're trying to cool the bathroom, you'll need a place to dump the heat produced by the other side of the unit. It'll also condense water if the bathroom is damp enough, so keep that in mind.

I don't know what the efficiency is on a Peltier unit, but a 1,300 watt a/c unit would probably do about 12,000 btu/hr (that is a wild SWAG, boys and girls!), so at a max your Peltier will do 1200 btu/hr, about a tenth of a ton. If the efficiency is as much lower as I suspect, it may be half of that.

Keep us posted on how that turns out!

Pahaska · 06-25-2003, 06:23 PM

The heat (or cold in the winter) will be vented into the main room of the trailer for the AC (heater in winter) to take care of. Keep in mind that my International has a phone-booth size bathroom. I don't need huge cooling/heating capacity since the bathroom is inside the outer insulation of the trailer.

Nice thing about the Peltier junction, a flip of a switch makes it a heater or a cooler depending on the season.

Chas · 06-25-2003, 09:53 PM

What the heck are you guys talking about?? Must be some kinda European setup? I saw something like it at Lowe's , I think? An a/c unit you can set inside your room but how the heck does it get rid of of the heat?? Looked like a dehumidifier to me.

I know in the computer rooms at work we would use portable "robot" a/c units, but would have to run a discharge duct up thru the ceiling to get rid of the condenser heat. They would also have a catch basin to get rid of the condensate water.

Chas

drboyd · 06-25-2003, 10:32 PM

Here's a link that describers Peltier coolers: http://www.marlow.com/TechnicalInfo/..._faqs.htm#th07

They note that the efficiency of heat pumping is pretty low, between .4 and .7. That compares to about 2.5 for a typical airconditioning unit with a compressor.

The bad news here is that the 130 Watt Peltier cooler will then remove about 130 times 0.7 = 91 watts of heat. That's 310 btu per hour, roughly the amount of cooling you would get by placing a couple of cold (40 deg) six-packs of beer on the counter in the bathroom and letting them warm to 80 degrees over the course of an hour.

Then again, it doesn't sound quite so bad if you say it that way, huh?

Phaedrus · 06-25-2003, 11:33 PM

I guess the days of just roughing it are over...lol

85MH325 · 06-27-2003, 08:26 AM

Thanks for all of your suggestions. I really like the ducting approach. I may have to see how that might work in my coach.

Thank God, the heavens opened up Wednesday afternoon and dropped the temps from the mid 90s to the low 70s for both Weds and Thurs nites!

I did ALL of the usual stuff, parked in the shade, used the awnings to shade the sides, used the attic vent fan in the BR(yes, that was apparently a factory-installed option in the pre-Fantastic Fan era) to vent the heat.

The problem was that the trailer had been in full sun during the trip to the campground, and then the bedroom on the curb side (last 5' without awning) was in the direct sun for several hours. The living room was reasonably cool with the air, until I directed ALL of the output to the rear, then the LR heated up. I decided it should be cool at least SOMEWHERE in the trailer, so I opened the LR ducts back up. I left our oscillating 14" desk fan at home (never again) so I didn't have any other way of moving the cool air to the rear.

Once it cooled down, it wasn't a problem to keep it cool, but it was still over 80 in the bedroom after midnight. It didn't cool down until sometime over night. Of course, the hull, the furnishings, and everything had heated up, so it took a LONG time to cool everything back down.

We'll have to see how it does on the weekend of the 11th!

Roger

**jcanavera** · 06-27-2003, 10:06 AM

I would be curious regarding the size of the A/C unit on your 34' trailer? I don't know what A/S is putting on them today, but in the 2001/2002 era the biggest Penguin unit was 13,500 BTU. I can tell you that my first camping trip out with my 27' Safari was in full sun at 100 degrees. We couldn't get the trailer down below 85 degees in the day and at times approached the upper 80's in the trailer.

We did every test in the book and the air conditioner was running to specs. I did a lot of checking and I do agree it was working to the best of its ability. Personally I think the unit is undersized and to put one of these in a 34' unit would probably yield the results you are experiencing.

Now we did go up to Jackson Center at their request to check for potential air leaks. One concern was that the wrong size unit may have been installed. Another was that the refrigerator compartment may have been leaking heat into the ceiling. As it ended up neither concern was an issue but they did realign my door. I have never been out in 100 degree full sun situations since that initial trip so I can't say that we have resolved anything. So far all is good.

I have seen some 34' units with 2 roof A/C which tells me that cooling in some situations has been marginal. Airstream now offers an optional 15,000 BTU Penguin so obviously they and Duo-Therm know that a bigger unit was needed.

I done a lot of talking to folks with the new bigger trailers and I've learned that cooling has not always been up to their expectations. I added a full streetside awning this year to the Safari in hopes of keeping the heat load down.

One of my conversations with the factory was the design limits for air conditioning. For example in St. Louis home air conditioning is sized to maintain a 20 degree spread between outside and inside temperatures. I was told that A/S has no specification.

Jack

drboyd · 06-27-2003, 10:55 AM

Well, yoou're probably right there about the sizing! The sizing is probably based on (a) what size units are available and (b) how much do they cost, rather than a full engineering heat load analysis. You may be down to either adding another a/c or ducting all the cooling to the part of the coach where you happen to be at the time...

Has anyone ever tried spraying down the outside of the coach right after sunset to cool it down? It might dull that gorgeous polish job if you had hard water, and it pretty much implies that you have tolerant neighbors and a supply of water, but that might help in marginal situations....

RoadKingMoe · 06-27-2003, 11:13 AM

In the driveway, our streetside points due west. Using the awnings on that side dramatically reduces heat gain into the trailer! Keeping the skylights closed during the day does also.

Spraying a trailer down with water is a great idea. Just make sure it isn't hard water. Ours at home leaves near-permanent water spots if you wash a vehicle with it.

85MH325 · 06-30-2003, 08:38 AM

Quote:

Originally posted by jcanavera
I would be curious regarding the size of the A/C unit on your 34' trailer? I don't know what A/S is putting on them today, but in the 2001/2002 era the biggest Penguin unit was 13,500 BTU.
Jack

Jack,

I checked the owner's manual this morning. The unit I have is a Dometic Duo-Therm 13.5k btu unit, Model #610015.306. I would guess it was probably the largest RV unit available in '94.

The owner's manual gives very explicit instructions to park the trailer in the shade, start the air early in the morning as it's easier to maintain a cool temp than to cool it down, use awnings, etc. etc. etc. All the stuff we already know. Basically, the owner's manual is telling me, in so many words, that the unit is inadequate to cool a hot trailer, but if you take all the right precautions it might be able to keep a cool trailer cool. So... now we know...

Roger

nds · 06-30-2003, 10:24 AM

Is the Penguin 13,500 BTU (model #600315) suppose to be more efficient than the regular Duo-Therm 13,500 BTU (model #610015)?

85MH325 · 06-30-2003, 10:27 AM

Quote:

Originally posted by nds
Is the Penguin 13,500 BTU (model #600315) suppose to be more efficient than the regular Duo-Therm 13,500 BTU (model #610015)?

Actually, I noticed on the trip back out to the trailer to put the manuals away that my DuoTherm does say "Penguin" on the control panel face... hmmm...

Mine is probably just the ten year old model...

Roger