Question for Ozz or whoever - Montana Owners Club

Alwims · 06-21-2011, 11:12 AM

What would cause my main roof air conditioner to frost over so bad that the fan can not blow through it? It doesn't happen all the time, but just enough that we are scared to leave it running when we go somewhere. Sometimes it'll go for 2 or 3 days and not do it and sometimes it'll do it 2 or 3 times a day. I seems to work fine and blows cold when it is working right.

Ozz · 06-21-2011, 11:27 AM

Generally it is not enough air blowing through the evap coil, the ducting in these trailers is minimum anyway. There is a freeze-stat bulb (a switch with a sensing bulb coming from it) this sensing bulb is clipped on the evaporator, it is a fail-safe control designed to switch off the compressor when it senses a freeze condition, then cycle it back on when not freezing. Yours may be: not there at all, clipped in the wrong place, off the face of the coil (un-clipped) or ??
The way you can leave with knowing it will not freeze over, if you can't find the bulb is to open the 'Dump' damper about 1/2 way, this will allow enough air out to stop the freezing.
Also, always run the fan on high. Mine has high med and low. It will not freeze as readily on high.

Trailer Trash 2 · 06-21-2011, 12:04 PM

Thats what happened to my air conditioner, I was lucky it was under warintee, the dealer had to replace that sensor Ozz is talking about on my coil, you can see it if you take the filter out and look up on the coil it a funny looking thing that is cliped to the coil with two wires comming out of it.

Im still leary about leaving the dog in the Monty for that one reason it freezing up and the dog suffers untill I got back.

Lambchop · 06-21-2011, 12:31 PM

Quote:

quote:Originally posted by Trailer Trash 2

Thats what happened to my air conditioner, I was lucky it was under warintee, the dealer had to replace that sensor Ozz is talking about on my coil, you can see it if you take the filter out and look up on the coil it a funny looking thing that is cliped to the coil with two wires comming out of it.

Im still leary about leaving the dog in the Monty for that one reason it freezing up and the dog suffers untill I got back.

Same thing here with the dogs. We set our Fantastic Fan on auto with temperature set for 80. If the A/C fails & we are gone..the Fantastic Fan kicks in for security. Also tell your neighbors to check on them too................

Roy

Ozz · 06-21-2011, 12:41 PM

Leave the dump damper open, it should never freeze then. I think....

Alwims · 06-21-2011, 01:41 PM

Thanks everybody. I'll do some checking tonight and get back to you.

Trailer Trash 2 · 06-21-2011, 02:15 PM

Quote:

quote:Originally posted by Ozz

Leave the dump damper open, it should never freeze then. I think....

what is a dump damper Ozz?

noneck · 06-21-2011, 02:23 PM

Dump damper is the one that sends the bulk of the flow right out of the unit verses going through the roof ducting...this is a design problem where there is too much static pressure limiting flow leaving coil temp to frost over if there is high humidity.
Ozz posted a potential help where he notes the louvers have excessive collar length and would help to shave them down so they do not protrude into the duct generating a flow obstacle which in turn impedes flow...
I too have experienced the freeze up and found Hi fan does help reduce the issue BUT I can't hear my TV!!! What a dilemma...watch TV at a civil volume or be cool...argh I want BOTH.

Ozz · 06-21-2011, 02:44 PM

I am going to post a thread for the Keystone folks addressing this A/C noise problem.

mhs4771 · 06-21-2011, 03:43 PM

That's part of the advantage of dual ACs. You can run the Bedroom AC and keep the bulk of the noise there, letting you watch the Tele without the vol at max. When we go to bed we reverse the process putting the noise in the LR not the BR. They sure are noisey devils, open the Kwik Kool vents and even more noise.

pineranch · 06-21-2011, 04:34 PM

Can't say much about the AC but Bose headsets sure take care of any noise while watching TV and makes the DW happy since my 30 year helicopter ears need volume.
Mike

Alwims · 06-21-2011, 04:43 PM

I learned a long time ago to run any roof air conditioner on high, if for nothing else, to keep it from dripping on the carpet or bed. OK, I opened the "Dump Damper" and am going to run it that way for a couple of days to see if that works. If it does work, I'm going to try closing it a little at a time till I find where it works best. Thanks everyone.

HOOK · 06-21-2011, 05:00 PM

I wanted the bedroom to be cooler one night when one of sons stayed over , so I opened the dump damper , turned the fan on low , the thing froze solid. Next night I turned fan switches on both A/Cs on high, set temp. cooler in bedroom and no further problems. Get as much airflow as possible to prevent freezing is my suggestion.

Ozz · 06-21-2011, 05:28 PM

The airflow is maximum through the evap coil with the dump damper open, it by-passes the resistance of the ducting. Trick is to not turn the fan on low, during evenings the pressures drop without any head pressure control, the propensity for it to freeze is greatest. That is where the freeze control comes in, that bulb on the evap surface.
You are correct on the fan speed.
The A/C makers know this happens, that is why the freeze control accessory is added. (on these RV units.)

Alwims · 06-21-2011, 05:55 PM

Sure is noisy with that thing open, but I guess we can get used to anything.

Ozz · 06-22-2011, 01:54 AM

Quote:

quote:Originally posted by Alwims

Sure is noisy with that thing open, but I guess we can get used to anything.

With the freeze control, you should be able to run it through the ducting. Try and see if the little control is on the face of the evaporator. You can look up there after taking a couple of screws off and removing the plastic cowling.

RickW · 06-22-2011, 04:43 AM

In our SOB we had the same thing happen. So we would only run the fan on High as well as have the fan setting to "on" instead of "auto". In the Monty we still only use High but we do allow the air to go down the ducts. We only use the dump when we first setup and are trying to cool the trailer off quickly.

SlickWillie · 06-22-2011, 06:23 AM

Might want to check the evaporator coils and be sure they are clean. Ours froze up solid recently. Cleaned the evaporator and she works just fine.

Alwims · 06-22-2011, 07:08 AM

Weeelll, I may be my own worst enemy. I'll explain, we have a rear kitchen so our Monty is divided into 3 sections. Kitchen, living area, & bath/bedroom. We have 2 air conditioners, one in the kitchen ducted and one in the bedroom, non ducted. Carol works nights and sleeps days so we close off the slider door from the living room when she sleeps. There are two vents from the kitchen air ducted into the bath and bedroom.

I decided, when we first bought this 5th wheel, since we had a bedroom air conditioner we didn't need the two vents in the bed/bath room so I blocked them off leaving only the two vents in the living room and the one in the kitchen. Shortly after that, we started having the freezing up problems, Duh. I guess I'm going to have to leave the dump about half way open to solve my problem. The noise in bearable with it half way open so if that solves our problem, we'll be happy campers. I'll keep ya'll informed.

Ozz · 06-22-2011, 08:58 AM

We all make a bo-bo occasionally, glad you caught it and have it stright now.

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