Heat pump issue

[Kentuckyguy]

Ok really stumped here. I have talked to a couple different RV techs and they are stumped as well. We own a 2016 376th with 3 rooftop units. Zone 1 is bedroom(ac only). Zone 2 is kitchen (ac/heatpump). Zone 3 is ac only. With the ccc2 thermostat in zone 2 (fan on auto) room temp 72 degree and heat pump set on 70 degree the unit comes on and blows cold air ( like AC cold). To get the heatpump to blow warm air, I have to set the thermostat 6 degrees above what the room temperature is. So if it’s 68 degrees in the room, I have to set the thermostat to at least 74 degree to get the unit to blow warm air. Now. Here another kicker. Once the room air comes up 1 degree then the unit starts blowing very cold air. As soon as that 1 degree difference goes back to 6 degrees then it will start blowing warm air again. It’s like it’s set on some kind of climate control. I have tried resetting the Tstate, a new thermostat, control board and even a new rooftop unit. All dip switches are set correctly. The unit is the 15k dometic brisk air 2. Thanks in advance for any help.

[FT4NOW]

Not sure if this applies to the heat pump portion, but there is a temp sensor that sits inside the intake side if I recall and it should be between the fins of the condenser. I wonder if that sensor fell out of place; again, not sure if this applies when heat pump is operating, just a thought.

On a different note, has the heat pump ever worked properly?

Other thought , if it's never worked properly, maybe the thermostat needs to be relocated. There have been cases of furnace discharge being too close to the thermostat causing weird operations. I know this is the heat pump, but same thought process.

Sent from my SM-G950U using Tapatalk

[Kentuckyguy]

Not sure if this applies to the heat pump portion, but there is a temp sensor that sits inside the intake side if I recall and it should be between the fins of the condenser. I wonder if that sensor fell out of place; again, not sure if this applies when heat pump is operating, just a thought.

On a different note, has the heat pump ever worked properly?

Other thought , if it's never worked properly, maybe the thermostat needs to be relocated. There have been cases of furnace discharge being too close to the thermostat causing weird operations. I know this is the heat pump, but same thought process.

Sent from my SM-G950U using Tapatalk

Relocating the thermostat wont change that the heatpump comes on when the room temp is higher than what the Tstat is set at.. Also when the temp in the room is higher that what the tstat is set at it shouldnt come on period or at least until the room temp get lower that what the tstat is set....

[dragonfly]

Ok really stumped here. I have talked to a couple different RV techs and they are stumped as well. We own a 2016 376th with 3 rooftop units. Zone 1 is bedroom(ac only). Zone 2 is kitchen (ac/heatpump). Zone 3 is ac only. With the ccc2 thermostat in zone 2 (fan on auto) room temp 72 degree and heat pump set on 70 degree the unit comes on and blows cold air ( like AC cold). To get the heatpump to blow warm air, I have to set the thermostat 6 degrees above what the room temperature is. So if it’s 68 degrees in the room, I have to set the thermostat to at least 74 degree to get the unit to blow warm air. Now. Here another kicker. Once the room air comes up 1 degree then the unit starts blowing very cold air. As soon as that 1 degree difference goes back to 6 degrees then it will start blowing warm air again. It’s like it’s set on some kind of climate control. I have tried resetting the Tstate, a new thermostat, control board and even a new rooftop unit. All dip switches are set correctly. The unit is the 15k dometic brisk air 2. Thanks in advance for any help.

Did you say you replaced the “rooftop unit”, I assume you replaced the heat pump on your roof?

[dragonfly]

Sounds like from your description, you are getting colder air than room air when your thermostat is calling for heat pump. This seems to indicate you are either in the heat pump mode that is in the defrost sequence thus cold a/c temperature air or you have something causing the switch over valve to switch to the wrong position(eg.air conditioning). If you replaced appropriate circuit board and thermostat you likely have a short in your thermostat wiring between the cooling and the first stage(heat pump circuit). This is just a guess without actually being there.
I hope it helps!

[Kentuckyguy]

Sounds like from your description, you are getting colder air than room air when your thermostat is calling for heat pump. This seems to indicate you are either in the heat pump mode that is in the defrost sequence thus cold a/c temperature air or you have something causing the switch over valve to switch to the wrong position(eg.air conditioning). If you replaced appropriate circuit board and thermostat you likely have a short in your thermostat wiring between the cooling and the first stage(heat pump circuit). This is just a guess without actually being there.
I hope it helps!

I am to the conclusion that I think it is in the wiring

[Kentuckyguy]

Sounds like from your description, you are getting colder air than room air when your thermostat is calling for heat pump. This seems to indicate you are either in the heat pump mode that is in the defrost sequence thus cold a/c temperature air or you have something causing the switch over valve to switch to the wrong position(eg.air conditioning). If you replaced appropriate circuit board and thermostat you likely have a short in your thermostat wiring between the cooling and the first stage(heat pump circuit). This is just a guess without actually being there.
I hope it helps!

Would it be possible that the defrost sensor that is pushed into the condenser is in the wrong area?

[Kentuckyguy]

Did you say you replaced the “rooftop unit”, I assume you replaced the heat pump on your roof?

Yes I did. We bought the camper in January of 2021. Never could get the heat pump to work. I have a tech come out and he tested the ambient air temperature sensor and said it was bad. He didn’t have one and couldn’t get one. I finally was able to get one and that didn’t fix the problem. That’s why we bout a new unit. We thought maybe the reversing valve was stuck. Then the new one was doing the same thing.

[JM0397]

Are there heat strips in the heatpump units?

In my residential heatpump, it works by slight degrees of temp change. When it's on and only working at a degree or two, then it's only the heatpump working and the air coming out feels cool, but if you measure it's a few degrees warmer. This is how the heatpumps work. The offset of 6 degrees usually means the aux heat (furnace or electric heat strips) also kicks on, hence the warmer air. A heatpump is highly efficient and can keep running and running, making it sound like nothing is happening but it is working as its supposed to.
Also note, heatpumps, at least residential, stop working around freezing. They work best in the high 30s-50s, and pretty much stop working into the 20s and down, hence why you don't see heatpumps in colder climates.

[Kentuckyguy]

Are there heat strips in the heatpump units?

In my residential heatpump, it works by slight degrees of temp change. When it's on and only working at a degree or two, then it's only the heatpump working and the air coming out feels cool, but if you measure it's a few degrees warmer. This is how the heatpumps work. The offset of 6 degrees usually means the aux heat (furnace or electric heat strips) also kicks on, hence the warmer air. A heatpump is highly efficient and can keep running and running, making it sound like nothing is happening but it is working as its supposed to.
Also note, heatpumps, at least residential, stop working around freezing. They work best in the high 30s-50s, and pretty much stop working into the 20s and down, hence why you don't see heatpumps in colder climates.

No heat strips. Themes have been in the mid to upper 40’s. We had a heat pump in our other camper and it worked just like our house heat pump. This one is working totally different.