Furnace Operation Question

[Jerald Cate]

I have a question I've been meaning to ask but keep forgetting before I get to the computer.  Are the roof (heat pump) units supposed to keep running when you have the thermostats set to furnace?  I only use my furnace setting when it gets below 40 degrees, which it has been here in Texas for a few days, and the heat pumps become ineffective.  Everything is working fine it's just the heat pumps keep running blowing essentially cold air.  It seems to me if they were shut down the furnace would be more effective.  I do set the thermostat fan speed on the low setting so the air from the overhead registers does not give a chilling effect.  The furnace registers blow a nice warm air.  The only purpose I can see in the heat pumps running is to help circulate the warm air from the furnace.  Is this correct or is my thermostats mis-wired?

[David T. Richelderfer]

Our thermostats do not work the way you describe yours to be working.  We have the 5-button Duo-Therm thermostats.  On the thermostats, the MODE button will rotate the LED screen vertically descending through MODE OFF, FAN ONLY, COOL, HEAT PUMP and FURNACE.  What ever operation we read on the screen is the only related device that will operate.  If we change the Mode from HEAT PUMP to FURNACE, for example, then the roof heat pump/fan will immediately shut down and the furnace/s will immediately turn on (assuming the air temperature and thermostat temperature setting is such that it/they should turn on).

[Steve Huber Co-Admin]

Bruce,
The HPs lose their effectiveness below 40F. Turn them off and use furnace setting (Aqua Hot) instead.
Steve

[Jerald Cate]

Thanks for the explanation David, I suspected I had an issue, I couldn't see any good reason for the heat pumps to continue running when the thermostats were set to furnace.  I had both air conditioner units replaced with the Dometic Penguin II units and Comfort Air Thermostats a couple of years ago and I've always suspected he didn't hook my thermostat wiring up correctly.  Maybe since my thermostats are different than yours I need to do as Steve said and just turn the thermostats off.  I'm so used to cycling through the modes, with the thermostat on, I hadn't thought of switching the thermostat off.  I'll try that tomorrow.  Thanks David and Steve.

[George Harwell]

Since you have replaced the a/c units I would suspect the dip switches in the unit on the roof are not set properly. That happens frequently when changing to a newer model. I have seen this several times in the past.

[Jerry Emert]

I have a question I've been meaning to ask but keep forgetting before I get to the computer.  Are the roof (heat pump) units supposed to keep running when you have the thermostats set to furnace?  I only use my furnace setting when it gets below 40 degrees, which it has been here in Texas for a few days, and the heat pumps become ineffective.  Everything is working fine it's just the heat pumps keep running blowing essentially cold air.  It seems to me if they were shut down the furnace would be more effective.  I do set the thermostat fan speed on the low setting so the air from the overhead registers does not give a chilling effect.  The furnace registers blow a nice warm air.  The only purpose I can see in the heat pumps running is to help circulate the warm air from the furnace.  Is this correct or is my thermostats mis-wired?

FYI same coach and mine do not work that way either.  It's either hot pump or furnace.
Jerry

[Paul Meehan]

Bruce, I believe when Steve suggested "turn them of," he was saying turn off the heat pumps not the thermostat.  The thermostat must remain on in the "Furnace" mode to signal the furnace to turn on.

[Mike Shumack]

Jerry are you running the furnace now while parked at your place? If so, what temp do you have it at?

It's supposed to be cold tonight but I don't think it's going to drop below 32 for long.

I just turned mine on and set the thermostat to 40 and the burner fired up. Maybe I should try to set it lower, like 35 degrees (I don't know how low the setting goes) - since I'm staying in the house.

[Jerald Cate]

Bruce, I believe when Steve suggested "turn them of," he was saying turn off the heat pumps not the thermostat.

Paul, I see your point but the only way my heat pumps will shut off is either power off the thermostats or shut off their panel circuit breaker.  I need to check the dip switch settings George mentioned but it's too cold to be out messing with that right now.  It's supposed to warm up this weekend I'll give it a look then.

[Jerry Emert]

Jerry are you running the furnace now while parked at your place? If so, what temp do you have it at?

It's supposed to be cold tonight but I don't think it's going to drop below 32 for long.

I just turned mine on and set the thermostat to 40 and the burner fired up. Maybe I should try to set it lower, like 35 degrees (I don't know how low the setting goes) - since I'm staying in the house.

Yes I have the furnace on to keep it from freezing more than the tanks.  I'm paranoid about the hydrohot.  I agree that it shouldn't be cold enough for long enough but a little bit of diesel will keep things warm.  50!
Jerry