Heatpump vs propane furnace cycling

[blangen]

Has anyone run into radically different temperature results when running "HEAT" (utilizing the heat pump until it gets too cold and then the furnace kicks in) as opposed to "FURN" (which, presumably, bypasses the heat pump but still uses the controls at the heat pump location)? I'm guessing, even though the remote control uses the electronics at the heat pump location, the furnace (only when in "FURN" mode) uses a different temperature sensor to control the cycling. Right?

Maybe I should begin at the beginning. Carrier V Heat Pump/AC and separate propane furnace. When on "HEAT", the heat pump runs until it gets too cold outside then, without any input from me, the heat pump turns off and the furnace kicks in. Then the furnace burner, cycling 3 or 4 minutes on and about 50 seconds off (the furnace fan stays on), runs the actual temperature in the coach up well beyond the 63 on the remote control. When I'd had enough cooking, I changed it to "FURN" and, although still a few degrees above the remote setting, the furnace is cycling reasonably. It heats, blower turns off, fan turns off after half a minute or so.

So... the question is... why is the furnace not cycling properly when on "HEAT" mode?

Thanks in advance for any help.

[dougrainer]

There are NO 2 sensors, Never has been. As to why, I do not know. As I stated, Carrier was not in the RV business long enough for Technicians to get a handle on the various problems with Carrier, especially the Remote control system units. Doug

[blangen]

dougrainer wrote:

blangen wrote:

dougrainer wrote:
When you have ONE tstat that controls both roof AC/HP and the furnace, there are NO separate tstats for the Furnace and the roof AC/HP. They utilize the same tstat sensor.
Since Carrier was not in the RV business that long, I have little experience with them. Is it possible that unlike other brand systems, you have to set the Furnace Temp separate from the HP temp on the remote? Even tho you are going to the default when it gets too cold? Doug

The tstat is a wireless remote and, yes, it controls everything. There are separate settings for each "MODE" setting. When in "FURN" mode, one can set the desired temp. When in "HEAT" mode, one can set a different temp (or the same). It is in "HEAT" mode that the heat pump runs until it gets too cold then the furnace kicks in... and that's when the temperature in the coach just runs up. In "FURN" mode, it cycles properly. What's interesting is that all of the controls are in the heat pump/AC unit on the roof because, even in just "FURN" mode, the remote needs to be pointed toward the roof unit to work and that's where the relays are heard.

What I think is happening is there are two temp sensors, one in the roof unit and one in the location of the furnace (under the kitchen cabinet). When in "HEAT" mode, even when it switches to the furnace, it uses the sensor in the roof unit (where it is colder). When in "FURN" mode, it uses the sensor located in the furnace on the floor. I don't KNOW this to be true but it seems like the reasonable answer. Also, rgatijnet1 (above) said he had two sensors. My original question was is there a way to fix this... so I didn't have to get up in the middle of the night to change from heat pump to furnace. Frankly, I don't really mind but I'd like to avoid the dirty looks from my wife when we wake up cooking. (Mostly kidding about the dirty looks) 🙂 Anyway... unless someone pipes up with a mechanical fix, I guess we'll just have to call this a design flaw. I'd love for someone to say there's a set screw to adjust something but that's just wishful thinking, I guess. Heck, if we're wishing, maybe I should just wish for a new coach with aqua-hot! lol

Sorry, NO, there is no separate tstat sensor other than the one for the roof AC. NO RV furnace would ever have the inside temp measured AT the furnace area. They are always mounted on either midway on the wall or in the roof in the center line by the roof duct work. There are some older RV's that have a separate wall tstat for the roof AC and another wall tstat just for the furnace. But, if you have a wall mounted electronic type tstat(or remote), the same sensor controls both the roof and furnace. From the Carrier Service manual.
14. Q) -- The remote control set temperature seems
to be off by 3 or 4 degrees from the ceiling unit.
Why is this?
A) The temperature is sensed at the ceiling unit,
not at the remote control. The temperature offset can
be even more with RV’s with higher ceilings. This is
more common in heat mode, as warm air rises. Doug

Interesting. So I'm entirely baffled as to why the furnace running through he heap pump in "HEAT" mode runs away in temp... to beyond 80 degrees but, in "FURN" mode, cycles properly just a few degrees above the tstat setting. Keep in mind that, in both modes, the tstat is set as low as it will go... 63 degrees. If not two different temp sensors, what could account for the difference?

Edit added: Does it matter that both the roof HP/AC and the floor furnace are ducted? It seems to make sense that a sensor could be at the air intake for the furnace.

[dougrainer]

blangen wrote:

dougrainer wrote:
When you have ONE tstat that controls both roof AC/HP and the furnace, there are NO separate tstats for the Furnace and the roof AC/HP. They utilize the same tstat sensor.
Since Carrier was not in the RV business that long, I have little experience with them. Is it possible that unlike other brand systems, you have to set the Furnace Temp separate from the HP temp on the remote? Even tho you are going to the default when it gets too cold? Doug

The tstat is a wireless remote and, yes, it controls everything. There are separate settings for each "MODE" setting. When in "FURN" mode, one can set the desired temp. When in "HEAT" mode, one can set a different temp (or the same). It is in "HEAT" mode that the heat pump runs until it gets too cold then the furnace kicks in... and that's when the temperature in the coach just runs up. In "FURN" mode, it cycles properly. What's interesting is that all of the controls are in the heat pump/AC unit on the roof because, even in just "FURN" mode, the remote needs to be pointed toward the roof unit to work and that's where the relays are heard.

What I think is happening is there are two temp sensors, one in the roof unit and one in the location of the furnace (under the kitchen cabinet). When in "HEAT" mode, even when it switches to the furnace, it uses the sensor in the roof unit (where it is colder). When in "FURN" mode, it uses the sensor located in the furnace on the floor. I don't KNOW this to be true but it seems like the reasonable answer. Also, rgatijnet1 (above) said he had two sensors. My original question was is there a way to fix this... so I didn't have to get up in the middle of the night to change from heat pump to furnace. Frankly, I don't really mind but I'd like to avoid the dirty looks from my wife when we wake up cooking. (Mostly kidding about the dirty looks) 🙂 Anyway... unless someone pipes up with a mechanical fix, I guess we'll just have to call this a design flaw. I'd love for someone to say there's a set screw to adjust something but that's just wishful thinking, I guess. Heck, if we're wishing, maybe I should just wish for a new coach with aqua-hot! lol

Sorry, NO, there is no separate tstat sensor other than the one for the roof AC. NO RV furnace would ever have the inside temp measured AT the furnace area. They are always mounted on either midway on the wall or in the roof in the center line by the roof duct work. There are some older RV's that have a separate wall tstat for the roof AC and another wall tstat just for the furnace. But, if you have a wall mounted electronic type tstat(or remote), the same sensor controls both the roof and furnace. From the Carrier Service manual.
14. Q) -- The remote control set temperature seems
to be off by 3 or 4 degrees from the ceiling unit.
Why is this?
A) The temperature is sensed at the ceiling unit,
not at the remote control. The temperature offset can
be even more with RV’s with higher ceilings. This is
more common in heat mode, as warm air rises. Doug

[redguard]

blangen wrote:

dougrainer wrote:
When you have ONE tstat that controls both roof AC/HP and the furnace, there are NO separate tstats for the Furnace and the roof AC/HP. They utilize the same tstat sensor.
Since Carrier was not in the RV business that long, I have little experience with them. Is it possible that unlike other brand systems, you have to set the Furnace Temp separate from the HP temp on the remote? Even tho you are going to the default when it gets too cold? Doug

The tstat is a wireless remote and, yes, it controls everything. There are separate settings for each "MODE" setting. When in "FURN" mode, one can set the desired temp. When in "HEAT" mode, one can set a different temp (or the same). It is in "HEAT" mode that the heat pump runs until it gets too cold then the furnace kicks in... and that's when the temperature in the coach just runs up. In "FURN" mode, it cycles properly. What's interesting is that all of the controls are in the heat pump/AC unit on the roof because, even in just "FURN" mode, the remote needs to be pointed toward the roof unit to work and that's where the relays are heard.

What I think is happening is there are two temp sensors, one in the roof unit and one in the location of the furnace (under the kitchen cabinet). When in "HEAT" mode, even when it switches to the furnace, it uses the sensor in the roof unit (where it is colder). When in "FURN" mode, it uses the sensor located in the furnace on the floor. I don't KNOW this to be true but it seems like the reasonable answer. Also, rgatijnet1 (above) said he had two sensors. My original question was is there a way to fix this... so I didn't have to get up in the middle of the night to change from heat pump to furnace. Frankly, I don't really mind but I'd like to avoid the dirty looks from my wife when we wake up cooking. (Mostly kidding about the dirty looks) 🙂 Anyway... unless someone pipes up with a mechanical fix, I guess we'll just have to call this a design flaw. I'd love for someone to say there's a set screw to adjust something but that's just wishful thinking, I guess. Heck, if we're wishing, maybe I should just wish for a new coach with aqua-hot! lol

I would have to agree its a design flaw.If it works exactly as you describe the only deal I can see is switch the Stat each day before bed time

[blangen]

dougrainer wrote:
When you have ONE tstat that controls both roof AC/HP and the furnace, there are NO separate tstats for the Furnace and the roof AC/HP. They utilize the same tstat sensor.
Since Carrier was not in the RV business that long, I have little experience with them. Is it possible that unlike other brand systems, you have to set the Furnace Temp separate from the HP temp on the remote? Even tho you are going to the default when it gets too cold? Doug

The tstat is a wireless remote and, yes, it controls everything. There are separate settings for each "MODE" setting. When in "FURN" mode, one can set the desired temp. When in "HEAT" mode, one can set a different temp (or the same). It is in "HEAT" mode that the heat pump runs until it gets too cold then the furnace kicks in... and that's when the temperature in the coach just runs up. In "FURN" mode, it cycles properly. What's interesting is that all of the controls are in the heat pump/AC unit on the roof because, even in just "FURN" mode, the remote needs to be pointed toward the roof unit to work and that's where the relays are heard.

What I think is happening is there are two temp sensors, one in the roof unit and one in the location of the furnace (under the kitchen cabinet). When in "HEAT" mode, even when it switches to the furnace, it uses the sensor in the roof unit (where it is colder). When in "FURN" mode, it uses the sensor located in the furnace on the floor. I don't KNOW this to be true but it seems like the reasonable answer. Also, rgatijnet1 (above) said he had two sensors. My original question was is there a way to fix this... so I didn't have to get up in the middle of the night to change from heat pump to furnace. Frankly, I don't really mind but I'd like to avoid the dirty looks from my wife when we wake up cooking. (Mostly kidding about the dirty looks) 🙂 Anyway... unless someone pipes up with a mechanical fix, I guess we'll just have to call this a design flaw. I'd love for someone to say there's a set screw to adjust something but that's just wishful thinking, I guess. Heck, if we're wishing, maybe I should just wish for a new coach with aqua-hot! lol

[dougrainer]

When you have ONE tstat that controls both roof AC/HP and the furnace, there are NO separate tstats for the Furnace and the roof AC/HP. They utilize the same tstat sensor.
Since Carrier was not in the RV business that long, I have little experience with them. Is it possible that unlike other brand systems, you have to set the Furnace Temp separate from the HP temp on the remote? Even tho you are going to the default when it gets too cold? Doug

[George_H]

Our Carrier does the same, temp unit is in the A/C opening in the ceiling. The heat pump circulates through the ceiling A/C ducts and does not do a good job of heating floor. Rather than use noisy heat pump during low temps. we just switch to furnace.

[rgatijnet1]

In my coach, I had two temperature sensors. One in the front near the driver's window and one in the middle of the coach, closer to the bedroom area. When I disconnected the front temperature sensor, the different systems, either heat pump or furnace, kept the temperature closer to what I really wanted and what was set on the main thermostat. .