A/C in Fiberglass Trailers

[Steven Tonnesen]

To me, the only place it makes sense for an AC in a trailer is on a small shelf in a closet. This way, the weight is almost directly on the steel frame and not adding to the weight on the fiberglass.

An inexpensive wall AC is all you need to get started. A key element in thinking is to take great liberties with the original intended design of the wall AC, and not to be afraid to cut away parts that do not matter for your installation. This means that you cut a big hole in the top of the wall unit's case. You also need to plumb a hole to drain the condensate. It is important that the condensate will not contact the wood, or you will rot your floor.

Basically, you have to create a place to put it, then create a path for the outside air to circulate through the condenser. The diagram shows how I did it in my Scamp. I built a small shelf, a stool of sorts, that fit just inside the bottom of the closet. The entire weight of the AC is supported on this shelf, which is resting directly on the floor, which is right over the steel frame. Drill a hole in the bottom of the AC and fit it with a hose that can extend below the wood floor. The blue line is the drain. Create a baffle inside the closet that separates the air flow coming out the condenser (the hot part) from the incoming air flow. Add a baffle separating the top part of the closet from the AC area, but leaving enough room for incoming air to reach the top of the AC, where of course you have cut a large hole. You will need to block air flow between the different areas of course, and there are numerous possibilities as to how to do that. I used some foam. I also used metal strapping and two turnbuckles to strap the AC onto the its shelf and the shelf was angle ironed to the floor. You do not want a heavy AC unit bouncing around inside your closet as you drive down the road.

This arrangement will give you a very cold camping trailer in the heat of the summer.


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[D Shubel]

Brilliant! Thanks for sharing your mod...with pictures!

[Loren G. Hedahl]

Is the reason you mounted it as high as you did, i.e., "on a stool" because of wheel well intrusion?

Is the space under the AC unit accessible?

[Steven Tonnesen]

Is the reason you mounted it as high as you did, i.e., "on a stool" because of wheel well intrusion?

Is the space under the AC unit accessible?

It is mounted as high as it is in order to make the controls easier to reach without bending so much. In addition, cold air sinks and hot air rises, so the cold output should be reasonably high.

Yes, the space under the AC is useable for storage. I don't remember if the wheel well was an issue or not.

[Loren G. Hedahl]

Your setup looks first rate and didn't lighten your rear pocket much. You'll enjoy it a lot down there in Florida, I'm sure. Up here where we live an AC is seldom needed. We just use a large after-market Max Air fan in the top vent. However, my vent fan ran a lot more than what you can buy a small AC for.

Do you remember, before the hackers swept this forum away, the fellow that installed his AC in the same location as yours, but did some ceative vent work so there were no penetrations on the side of the trailer? The air intake and exhaust were through the floor.

As I remember, the reason for his doing this was because his favorite camp ground charged more if the trailer had an AC whether it was weather when AC would be used or not. With nothing visible from the outside indicating that the trailer had an AC, he got his admission for the cheaper price.

[Per Walthinsen]

Last year I installed an AC with the vents through the floor and documented it here on the forum which went poof. The idea was to not penetrate the sides of the Burro but it was more an exercise into seeing if I could do it and get it to work.

5000+ BTU, mounted in the rear under-bed cabinet, with helper fans to counteract the drag of the necessary ducting. Lightweight 40lb unit with electronic controls which were hacked into for remote operation (and an actual remote). We use the rear area as a permanent bed, so the space used was next to inaccessible anyway.

Works very well, shoots the cold air up into the ceiling along the centerline, so the distribution is close to ideal. Quiet and unobtrusive even.

I would not really recommend making such a setup unless you really enjoy tinkering with things and happen to have the relevant skills and patience. If you do, though, it can be very a very satisfactory solution.

[Per Walthinsen]

Another view.

[Per Walthinsen]

And another.

[Brian B-P]

Per, I remember the original discussion, but don't recall seeing these pictures. The is truly the coolest - in every sense of the word - A/C install I've heard of!

Steven, you have a nice tidy installation too!

[Gary Little]

And another.

Per,
What brand of AC is that? I have never seen one that small. I am in the process of installing one in my 13' Scamp. I have choosen the porta- potty space as the best place(I know it is very low) but I think with the correct sizing it will work. I will then place the porta potty in the clothes closet since it is raised about 6". This will be just like having a real toilet. I tried ducting the AC exhaust heat thru a 4" hole but it was to restricted. Unit was pulling almost 7amps. It normally only pulls 5amps. Again where did the small unit come from?
Thanks,
Gary little

[Per Walthinsen]

Gary:

Sears Kenmore, Model 580.74055
I searched the "Internets", knowing the amount of room I had available and compared the physical dimensions of quite a few models. This was the smallest: 17-5/16" wide, 11-1/8" high, and 12-13/16" deep. 39 lbs.
(5,150 BTU, 530 watts or 4.9 Amps, EER of 9.7 Btu/hW.)

Adequate airflow was the name of the game, with a 6" duct intake for the "exterior" circuit and dual 4" ducts for the exhaust. A short 4" duct for the interior cold air. Even with the vent plenums generously calculated the airflow was not adequate since the AC's blower had been carefully calibrated to the unit without the ductwork. Since I hacked into the electrical supply lines for the compressor I was able to connect a relay (Dayton 5YP97) to drive two squirrel-cage helper fans (Dayton 4C446 from Grainger), one for each circuit. Big difference.
The outlet for the cold air was deliberately aimed up for the obvious reasons, but this unit by itself throws the cold air up at about a 45 degree angle, so it could probably do pretty well by itself even mounted in a low position.

[Gary Little]

Gary:

Sears Kenmore, Model 580.74055
I searched the "Internets", knowing the amount of room I had available and compared the physical dimensions of quite a few models. This was the smallest: 17-5/16" wide, 11-1/8" high, and 12-13/16" deep. 39 lbs.
(5,150 BTU, 530 watts or 4.9 Amps, EER of 9.7 Btu/hW.)

Adequate airflow was the name of the game, with a 6" duct intake for the "exterior" circuit and dual 4" ducts for the exhaust. A short 4" duct for the interior cold air. Even with the vent plenums generously calculated the airflow was not adequate since the AC's blower had been carefully calibrated to the unit [b]without the ductwork. Since I hacked into the electrical supply lines for the compressor I was able to connect a relay (Dayton 5YP97) to drive two squirrel-cage helper fans (Dayton 4C446 from Grainger), one for each circuit. Big difference.
The outlet for the cold air was deliberately aimed up for the obvious reasons, but this unit by itself throws the cold air up at about a 45 degree angle, so it could probably do pretty well by itself even mounted in a low position.

Thanks Per,
It looks winder than 17 5/16" it must be the camera angle. I think I may have found another option. My hull is in excellent condition for a '86 and I hate to start cutting holes in it. I read on the forum about a "Freecom" unit. It is a 4000 BTU portable 10.6" wide 25.8" tall and 14.5" deep. It will fit in my pantry perfectly. I just hope it is still available. The member speaking about it stated that they haven't heard from the company. And they don't sell at retail stores according to their web site. Do you have any input about this unit?

Thanks,
Gary Little
Gary

[Per Walthinsen]

Gary:
For the compartment under the bed of my Burro the width was not an issue, but height and depth was, so it fit the bill there. Ours is a double hull with insulation so you'd think it is on par, insulation wise, with the Ensolite, etc. of other brands. My unit is small, so the cooldown takes longer than the 13000 BTU roof units, but it does a good job for the space even though the interior volume is larger than most. Advantage to this unit is that it has multiple choices for delayed turn-on or turn-off times.

I'd guess that 4000 BTU is pretty small, even for a 13 footer, so I think I wouldn't do it. In any case, I'd plan carefully for condensate drain piping.

If by portable you mean the kind with wheels and hoses that you can put wherever you want, I'd recommend a search. You may be dismayed at the comments. In any case, a unit without both intake and exhaust hoses is something I'd avoid. The concept of only one hose is flawed.

Note that I only cut holes in the floor (3/4" plywood with fiberglass on both sides) of my trailer to avoid any more sidewall cutouts. Bonus, with vented boxes protecting the holes underneath, is that the chance for water leakage is virtually nil ("water in the hold" being something I want to avoid at all costs).

[Brian B-P]

...I read on the forum about a "Freecom" unit. It is a 4000 BTU portable

I assume that this is the RCS-M1000T. This is the type of hose-equipped unit which we have discussed before and to which I believe Per is referring. This unit is indeed a single-hose design, and I agree with Per that this is a bad idea. The User Manual suggests that use of the hose is optional for cooling operation, but that's nonsensical - to cool, you must remove heat, and it has to go somewhere. They apparently expect you to place it in front of a doorway or open window, but without the exhause hose blowing the hot air somewhere outside the trailer this unit would only work as a dehumidifier.

We have a larger two-hose unit of a different brand at home, used in the living room, and it is quite effective but very bulky and heavy.

By the way, this company's website describes various types of air conditioners, including a "ductless mini split" design which has separate indoor and outdoor units connected by plumbing. This is a standalone version of central A/C, is available from several companies (such as Panasonic), and seems like an interesting approach to me. I'm thinking of the outdoor unit on the tongue or rear bumper, and the indoor unit in an upper cabinet. Has anyone tried this sort of setup?

[Gary Little]

I assume that this is the RCS-M1000T. This is the type of hose-equipped unit which we have discussed before and to which I believe Per is referring. This unit is indeed a single-hose design, and I agree with Per that this is a bad idea. The User Manual suggests that use of the hose is optional for cooling operation, but that's nonsensical - to cool, you must remove heat, and it has to go somewhere. They apparently expect you to place it in front of a doorway or open window, but without the exhause hose blowing the hot air somewhere outside the trailer this unit would only work as a dehumidifier.

We have a larger two-hose unit of a different brand at home, used in the living room, and it is quite effective but very bulky and heavy.

By the way, this company's website describes various types of air conditioners, including a "ductless mini split" design which has separate indoor and outdoor units connected by plumbing. This is a standalone version of central A/C, is available from several companies (such as Panasonic), and seems like an interesting approach to me. I'm thinking of the outdoor unit on the tongue or rear bumper, and the indoor unit in an upper cabinet. Has anyone tried this sort of setup?

Why would you need a second hose to pull air into the unit to cool the compressor? Will air not be pulled in through the side grills? I do plan on piping out the exhuast through the floor or a small port out of the side.
Thanks,
Gary Little

[John McMillin]

Nice installation, Steven. It's close to what I came up with last summer. I used a rubber dish drain tray beneath the A/C to catch the condensate and drip it out the old fridge hatch. I used an AC fan on the floor to blow the cold air upwards, and anoher small box fan to help blow the hot air outside, sandwiched between the back of the unit and the eggshell. I used a cam-lock bargo strap to secure the AC to the shelf.

It all worked great in extreme conditions: Kentucky and Tennessee last August, 95 and 95% every day. Total cost, including used air conditioner and other supplies: $75.

[Suz]

If by portable you mean the kind with wheels and hoses that you can put wherever you want, I'd recommend a search. You may be dismayed at the comments. In any case, a unit without both intake and exhaust hoses is something I'd avoid. The concept of only one hose is flawed.

[b]Portable Units: Unfortunately, a lot of really good information and discussions were lost in the hijack. If it was available, you would have been able to read about those with first hand experience with them.

It was a good concept, but it just didn't quite work out. As I recall, the cooling was limited - especially in humid climates.

[Brian B-P]

Why would you need a second hose to pull air into the unit to cool the compressor? Will air not be pulled in through the side grills?...

Well, it's not the compressor which needs cooling, but the condensor coil, but the idea is the same - some source of air is needed to dump the heat into. If there is not an intake hose for that air, it will be taken from inside the trailer, and that will be replaced by more hot and humid air from outside through whatever path is available. The better plan is to pull outside air over the condenser, and send it back outside again.

The inside and outside air paths are normally quite separate in any air conditioner, except these one-hose portables; inside air goes over the evaporator to get cool, outside air goes over the condenser to pick up heat. Most people don't have central air conditioning in their house, but do in their car, so I'll use that for illustration - the A/C condenser in a car is that extra radiator ahead of the engine radiator, fed outside air and not exposed to the air inside, while the evaporator is in the heater/fan setup under the dash (along with the heater core), absorbing heat to keep the inside air cool. For another example, in-window units draw air from the outside for the condensor, which is properly considered and nicely shown in Steven's original post to start this topic.