Heat Pump Issue - Montana Owners Club

wprantera · 11-07-2018, 02:00 PM

Has anyone had an issue with their rear heat pump? During a Halloween camping weekend weather was chilly but not below freezing, so I decided to just you the rear AC heat pump. My issue is that it was all ice up when I went up to the roof tut o check for debris on the slides. See attached pictures. Do I have a problem?

CarWin · 11-07-2018, 06:16 PM

Quote:

Originally Posted by wprantera

Has anyone had an issue with their rear heat pump? During a Halloween camping weekend weather was chilly but not below freezing, so I decided to just you the rear AC heat pump. My issue is that it was all ice up when I went up to the roof tut o check for debris on the slides. See attached pictures. Do I have a problem?

YES you have a problem.............There is NO pictures attached for us to see.

jimcol · 11-08-2018, 06:04 AM

If your heat pump was iced up there is a problem. I'm confident of that even without a picture.

wprantera · 11-08-2018, 01:31 PM

How do you post pictures?

wprantera · 11-08-2018, 01:41 PM

http://www.montanaowners.com/forums/...hp?albumid=161

wprantera · 11-09-2018, 04:31 AM

I think I did it with a little help. Thank you

wprantera · 11-09-2018, 04:31 AM

Does anyone have any ideas on how to fix or what's wrong?

CarWin · 11-09-2018, 11:43 AM

I`m NOT an ac/heatpump mechanic, but anytime Ive had frozen coils like this its either been low freon or excessively dirty coils causing it.

Others may have a better idea.

jstadler · 11-14-2018, 04:14 PM

There is a sensor under the foam insulation that detects a frozen coil. It may not be positioned properly or is defective. You can talk to the MFG and they will provide you trouble shooting ideas. A frozen coil is a result of the other posts and the sensor. A simple system, I would be concerned if it did not exchange cold air for heat.

John

TAKPAK · 11-14-2018, 04:52 PM

You may or may not have a problem. The heat pumps/AC systems on these RV's use a small coil, compared to a residential unit. It's basically the same coil they use for strictly cooling units on RV's, but now also use it for extracting heat as well. Because of that, the heat pump doesn't really "heat" very good at anything below 45 degrees outside air temp. Any OSA temp below that, and there just isn't enough "heat" in the air to work well. Getting down around 32 degrees and the coil may very well "freeze up" due to being "overworked" and not enough surface area. I did a test on ours, and pretty much anything below 45 degrees OSA and the pump couldn't really keep up. When OSA dropped to 40 degrees it was a losing battle. Then it's time to bring on the furnace and get the temps back up. Anything above 45 OSA, and the heat pump part works really well.

CarWin · 11-14-2018, 05:00 PM

TAKPAK, thats good info to have in the memory bank,Thanks for posting it!!

Dave Sinclair · 11-14-2018, 06:25 PM

What he said. Anythign below 45 and there is NO heat to extract, so no work and you get freeze up.

cwestl · 11-14-2018, 06:42 PM

I can see we don't have any AC Guys in the forum. Any heat pump will ice up the outside coil while heating. Same with you home unit if you have a heat pump. Sensors will sense this condition and put it in a defrost mode to melt the ice off the coil. Then it should go back to heating. Of course Home heat pumps will work below 32 Deg. Of course the units on Travel Trailers have a lot smaller coils and are not as good collecting heat from outside air.

TAKPAK · 11-20-2018, 09:33 AM

Quote:

Originally Posted by cwestl

I can see we don't have any AC Guys in the forum. Any heat pump will ice up the outside coil while heating. Same with you home unit if you have a heat pump. Sensors will sense this condition and put it in a defrost mode to melt the ice off the coil. Then it should go back to heating. Of course Home heat pumps will work below 32 Deg. Of course the units on Travel Trailers have a lot smaller coils and are not as good collecting heat from outside air.

Well cwestl, I'll have to beg to differ about AC guys. I was in the industry for 32 years. You are correct that a heat pump will ice up, under the right conditions, and if it IS low on charge, it will ice up sooner. We could get into enthalpy, latent heat, dew point and all that, but for this forum it's not needed. I have not checked personally, and there may be a "defrost mode" on the RV heat pump but not observed it in operation yet. My observation on when the heat pump ceases to be practical was based on taking measurements of the return air and the discharge air temps, and observing the outside air temp. What I found was at around 45 degrees OSA, the insided return temp and the discharge temp were virtually the same, therefore for the work the heat pump was trying to do, there was no gain. No sense in "working it to death." And the RV heat pumps to my knowledge don't have an electric (or supplimental) backup heat source, like the home units do. I guess you could always turn on the electric fireplace or heater inside, but that kind of defeats the purpose, and possibly could blow the breaker! Live and learn, eh?

Mikendebbie · 11-20-2018, 12:00 PM

Heat pump on the bedroom unit?
Specs say heat pump occurs on "main air conditioner" - same as the living room unit...

For what it's worth - we were in Houston last week when a cold front blew through and dropped nighttime temps to 30*. I tried our heat pump for the first time to see how it would do. Set the living room T-stat on heat pump+low fan speed and set temp to 67*. We like the "white noise" generated by the AC fans at night. Bedroom unit was off. I had to get up around 2 am to turn the setting down because it was getting too stuffy for us, but we like to sleep cold. I backed it down to 60*. The thing seemed to take the chill out of the air, so I suppose it did its job.

I suppose next time I might try the heat pump+auto setting to see how well it works...but I don't like the sounds/lack of sound of AC or furnace cycling on and off. I prefer constant white noise of a fan.

jetskier · 11-20-2018, 12:45 PM

Quote:

Originally Posted by Mikendebbie

Heat pump on the bedroom unit?
Specs say heat pump occurs on "main air conditioner" - same as the living room unit...

For what it's worth - we were in Houston last week when a cold front blew through and dropped nighttime temps to 30*. I tried our heat pump for the first time to see how it would do. Set the living room T-stat on heat pump+low fan speed and set temp to 67*. We like the "white noise" generated by the AC fans at night. Bedroom unit was off. I had to get up around 2 am to turn the setting down because it was getting too stuffy for us, but we like to sleep cold. I backed it down to 60*. The thing seemed to take the chill out of the air, so I suppose it did its job.

I installed the 3rd AC last month and I ordered the new unit with the heat pump to match the rear main unit. I put it in the bedroom so I could run both in the heat pump setting in the ducted system. The original front when to the kitchen for cooling only. The system worked well even down to 35°. It didn't do too well at or below freezing. I did try it too! I had to kick on the furnace for a bit when it dropped into the teens. I ran the fan in auto because it was blowing cold air when the unit was not heating on low.

Bkuhn · 10-13-2022, 10:16 PM

Thank you. I brand new, not familar with heat pumps. Its about 37 out now, and heat pump puts out heat, then just runs... no heat, then kicks in heat. I was not sure if ok to leave run. But with your explanation I will not run under 40 or 45
Thank u
You

Daryles · 10-13-2022, 11:12 PM

Lots of good info here. Thanks for sharing your knowledge.
The only thing I can add is sometimes they don't install the AC units correctly and omit placing the freeze sensor on the coils.

Cat320 · 10-15-2022, 11:29 AM

I solved my heat pump issue...I don't use it.

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