Basement air is freezing up

[Doug Sage]

I have the RVP Products basement air conditioning in my 2007 Itasca Suncruiser 38J. We are parked in North Salt Lake, Utah and it was in the 80s today. The humidity according to the National Weather Service varied between 15% and 25%. When the outside temperature was 82° and I had the inside thermostat set at 74° the unit froze up. Then I turned off the second breaker so that it would only run on the first compressor and at least give us some cooling. Of course that didn't help and it wasn't really any cooler inside than outside. This has been going on for quite a while. I have replaced the air filter with a low restriction clean filter. The temperature difference with both compressors running is 20° to 25° and it is about 16° with only one compressor running. What it boils down to is that I can only run the first compressor if the outside temperatures are about 82 or less even if I am in the desert with low humidity. Otherwise the A/C freezes up and stops running until it thaws. Can anyone give me a good idea as to what is wrong? Can anyone give me a referral to a service person who knows what they are doing with these basement air conditioners?

[KIX]

Cooling freeze thermister if there are no air restrictions.
Do you have schematic to identify where it is?

You could try to remove any air restriction like your air filter. have you cleaned the indoor coil recently?

[amanda_h]

I was also going to suggest to see what happens if you take that low restriction filter out. Even though it's "low restriction," it still could be limiting air flow. We were told to use the cheap cardboard framed filters and replace them often as the fancy expensive filters sometimes restrict too much air flow. Ours came with the cheap cardboard-framed blue filter from the factory when the coach was brand new and we've replaced them with the same ever since as they cost less than a dollar.

[amanda_h]

Doug, I keep a journal of recommendations when we meet people in RV parks and start to chat about things. If they have a good recommendation as to service they're received, I write it down for future reference. It's sort of my own RV Service Reviews resource.

In looking through my notes, I see that Arv's Trailer Repair in the Ogden is recommended by a couple who live in the SLC area. Arv's is an factory authorized RVP service center. The date that is on my notes is almost two years old, though. So I'm not sure if they're in business or not ...all I have written is that they are a factory authorized Coleman RVP service center. Of course, as has been said before, many residential a/c repair facilities can diagnose and repair these units.

[MntDriver]

Join the crowd! Ours is the same way up here in the high country with low humidity. Ours never drips outside when the humidity is low. We run ours until the air flow decreases somewhat, then leave fan on while turning off both compressors (thawing the coil), and then starting all over for several more hours. FrontrangeRVer has some old posts on this subject here if you do a search. Lots of us have installed an extra roof air to supplement our basement airs....see my sig. Join us at the Winnie Forum at RVForum.net about this subject.

You will never fix this problem....won't happen.

[TXiceman]

First thing to check is low air flow due to restrictions and/or bypassing at the unit.

And yes you can freeze up a unit in low humidity conditions, especially if you run the fan on low speed. Always run the fan on High speed.

The load on the unit is two parts; sensible (cooling of the air dry bulb) and latent, (removal of moisture ...related to wet bulb). In a dry area, there is little latent load which is the largest load on a unit in a damp area. The compressor is a positive displacement device and pumps a given volume of gas with eash compression cycle. If the load is not present on the evaporator, it will not vaporize the refrigerant and the compressor will continue to pump and reduce the presure in the evaporator coil which also reduces the temperture to the point that you will be operating the coil below freezing. The unit will self-balance at this lwer temperature. All is OK until you drop below the freezing point and ice forms on the coil.

With the low humidity, try running at a bit higher ambient temperature and run the fan on high speed.

There is remote possibility that the unit may be low on refrigerant, but that is not something easily checked or repaired on these hermetic units.

ken

[HD4Mark]

This may not be your model AC but the diagnostics could help.

[Doug Sage]

I agree that it seems like the indoor coil could be dirty or the cooling freeze thermister could be faulty. I am using the cheapest paperboard framed filters available. I don't see how I can clean the indoor coil without at least partially removing the A/C unit. I don't know how to get to it. It would have been nice if it was designed with a panel that could be taken off to give access for cleaning. I always keep the fan on high. It seems to me like this has been gradually getting worse over time. I'm not sure setting the thermostat warmer will make any difference since it only cools the inside down to 80 when it is 82 outside. This wouldn't be affected at all by setting my thermostat up from 74 to 78. I am leaning toward the cooling freeze thermister but that will take someone experienced to replace. I can't do it.

[Fossilhog]

Originally Posted by Doug Sage

I agree that it seems like the indoor coil could be dirty or the cooling freeze thermister could be faulty. I am using the cheapest paperboard framed filters available. I don't see how I can clean the indoor coil without at least partially removing the A/C unit. I don't know how to get to it. It would have been nice if it was designed with a panel that could be taken off to give access for cleaning. I always keep the fan on high. It seems to me like this has been gradually getting worse over time. I'm not sure setting the thermostat warmer will make any difference since it only cools the inside down to 80 when it is 82 outside. This wouldn't be affected at all by setting my thermostat up from 74 to 78. I am leaning toward the cooling freeze thermister but that will take someone experienced to replace. I can't do it.

I was able to access the cooler with an extension and brush on my vacuum cleaner thru the filter openings.

[KIX]

Doug, Actually removing the A/C from the coach is pretty easy. The electric stays attached so it can be run "on the ground". The duct that runs up the back of the coach is attached with a multitude of screws but not too hard to remove. Beyond that it just takes a little muscle to slide it out. At least that's the way mine comes out. With it out and on a couple of upside down 5 gallon pails it's easy to service. Change the bearings and outdoor blower wheel in addition to cleaning the indoor coil. Oh, and install a new thermister while you're at it. All that can be done in an afternoon. Good luck.

Just noticed that Fossilhog has a good idea but be very careful to not bend the fins

[HD4Mark]

Also try this link for a great write up on servicing a basement AC by Duner
http://sites.google.com/site/billmarie2008/

[grtharris]

Just a thought, the moisture freezing on the evaporator coil is coming from inside the coach. Be sure and run the bath exhaust fan when taking a shower and the stove exhaust fan with cooking.
This should help reduce the moisture load on the evaporator.

[Doug Sage]

Originally Posted by grtharris

Just a thought, the moisture freezing on the evaporator coil is coming from inside the coach. Be sure and run the bath exhaust fan when taking a shower and the stove exhaust fan with cooking.
This should help reduce the moisture load on the evaporator.

Yes, we always run the fan under these circumstances. Thanks for the tip.

[Ron & Dee]

The evaporator coil, cooling coil, should never freeze. You are talking about coils running at 32 degrees or below.

If your evaporator is freezing you either have a restricted air flow or a refrigerant leak.

Ron