Moisture/Humidity in rear bed area

We finally took our new TM out for its maiden voyage this past weekend, and noticed that the rear bed area felt a little humid at night. Since the AC isn't controlled with a thermostat, when it reaches the desired temp, it simply runs the fan without the compressor -- which was drawing in damp, outside air. (One of the reasons we chose the TM over a canvas pop-up or hybrid was the notion that the hard-sided TM would keep out the humidity to provide better sleeping comfort.)

We went to Wal-Mart and purchased a $50 de-humidifer to use for the second night ... it seemed to work (the sheets didn't have that awful "moist" feeling), but I'm wondering if there's a better solution.

Can a thermostat be installed to the roof AC unit so that it simply shuts off instead of drawing in outside air, just like the AC at home?

- Mark

[mjlaupp]

Quick Answer - Yes.

How much time and $$ do you want to spend?

To have a remote thermostat requires fan/compressor control relays at the A/C. You would have to replace the inside air handling deflector along with the existing controls. Coleman makes several different deflectors with various levels of control. You would then have to run thermostat wire through the upper shell and out to a thermostat mounting location on one of the cabinets.

MJL

You might want to have your A/C checked. I live in south Texas where humidity is never below 90% and I don't have any problem with moisture. I have actually been quite impressed. Only problem is A/C condensation sometimes drips on the floor. Dave

[Bill]

I'm not at all sure that the air conditioner draws in outside air. I think that it simply recirculates the inside air, much like the RECIRC setting on your car A/C. By doing so, the air is cooled and dehumidified with each pass through the unit, as long as the compressor is running. I could be wrong about this, and would welcome any expert input, but ....

The owner's manual for the unit does not directly state that air is recirculated, but the section covering the filter hints strongly at it, saying that if the filter is clogged, air circulation will be reduced. It also says that if the unit is operated without a filter, all of "the lint, dirt, grease, etc that are normally stopped by the filter are now accumulating on the cooling coil." Of course, I am quoting from the manual for the Coleman low-profile unit in my TM, but I bet yours is similar. Check your manual, either the paper copy or online. Coleman stuff shows up at www.RVComfort.com.

Many upper-tier window air conditioners have an "Outside/Recirculate" lever. If a particular unit doesn't have it, it defaults to "Recirc". But the TM roof unit does not have such a control, and simply recirculates.

Inside air can build up humidity from several sources. These include cooking, running an unvented catalytic heater, and the breathing of the occupants. At night in summer, you probably weren't doing the first two, and simple breathing shouldn't build up the humidity too fast. So let me ask, are you sure that the celing vents and all the windows and the door were tightly closed? Was the Fantastic Fan turned off? It is very quiet on the Low setting. If the outside air is humid, any of these could overwhelm the ability of the A/C to remove humidity.

Bill

Interesting, Bill. I just assumed that it was using outside air, but it sure sounds like I could be wrong on that.

I'm going to take the TM out a few more trips before ultimately deciding, but here's a question -- why wouldn't the factory place a thermostat on the A/C controls as well? Seems like doing so would significantly reduce wear-and-tear on the unit, as it wouldn't have to constantly stay on.

Another question -- could I just go out to Home Depot and buy an inexpensive digital thermostat and place it where the furnace thermostat is ... and run some kind of wire from it to the A/C unit to control both (much like the setup in a home)??

Meantime, we're going to place the compact dehumidifier in the back bedroom area on our next trip this weekend to see if that helps.

- Mark

[Bill]

Originally Posted by radiojon

We finally took our new TM out for its maiden voyage this past weekend, and noticed that the rear bed area felt a little humid at night. Since the AC isn't controlled with a thermostat, when it reaches the desired temp, it simply runs the fan without the compressor
- Mark

Mark -

I'm not sure what you mean when you say the A/C isn't controlled with a thermostat. Isn't there a knob on the A/C unit itself that says "Warmer-Colder" or "Red-Blue" or something similar? This is what sets the temperature, and it is indeed a thermostat, even if it isn't calibrated in degrees. In fact, this is what makes the compressor cut off.

Th reason that the fan stays running even when the compressor is off? If you turn off the fan, room air does not circulate over the thermostat, so the thermostat doesn't know when the room needs more cooling. By running the fan, the thermostat can sense when room temperature rises, and turn the compressor back on again.

If you wanted to experiment, it is a simple rewiring job to make the fan turn on and off at the same time as the comprerssor. Simply move the fan's power wire to the same place as the compressor's power wire. I wouldn't advise doing this unless you are familiar with electricity and comfortable doing house wiring, though.

What make and model A/C do you have?

Bill

[rtcassel]

This is a link to remote control for Coleman Mach A/C, including thermostat:
http://www.campingworld.com/browse/s...27169&src=SRQB