Seneca cabin heat.

[Mwade]

I own a 2015 Seneca. I have a question as to how the heater systems work. The Seneca has two roof air conditioners with heat pumps that are good to about high 30's. when the temp reaches below the high 30's, the heat pumps shut down, and the regular propane heat system takes over. This is all good, but I have some questions. Which wall regulator operates the propane heater? As far as I can figure out the front regulator operates the propane furnace. So I guess the rear regulator should be left off, and only operate the front air conditioner when using the propane heat. Last night I was using only the rear air conditioner for heat. Hot air would circulate from the rear bedroom to the front of the coach via the roof air vents, all is good. Then the temperature got cold enough that the heat pump shut down, and would blow cold air. I shut the rear unit down, and started the front unit. The propane heat finally fired up, and hot air was coming from the floor vents. But cold air was still coming out the roof air conditioner. I gave it several minutes, and finally hot air was flowing through the roof vents, and the front air conditioner. Is this how the units are supposed to work?

[Robbbyr]

The front thermostat does indeed control the gas furnace as well as the front A/C - Heat Pump.

When the front thermostat is set to gas heat the furnace will cycle as necessary to maintain the desired set point. As you probably have seen, first the furnace's fan starts - then the burner kicks on to generate heat - then when the thermostat is satisfied the burner shuts down. Then shortly thereafter the furnace fan shuts down. It runs for awhile to cool off the furnace's heat exchanger

I do not run the A/C fan when I am using gas heat, since as you state it just seems to blow cold air overhead. So I leave the front A/C fan control in "Auto" which keeps the overhead A/C fan from running. So the only fan that runs is the furnace one as it cycles. There is no way (as configured) to continuously run the furnace fan, it cycles with the burner when the front thermostat calls for heat.

In weather that requires the furnace I do leave the rear A/C control off.

As you may have noticed when you do use the "Elec Heat" setting on the front A/C - Heat Pump - if it is too cold the gas furnace will kick on. That is by design, if the room temperature is a certain amount (or more) below what you have the thermostat set for the gas furnace will light to bring the temperature up more quickly.

As far as warm air from the overhead vents - If the heat pump is able to run (outside air temp high enough) it will warm up in a few minutes. If it is too cold for the compressor to run it will stay cold until you warm the coach enough with the furnace so that it is circulating that warm air. There is no "connection" that takes furnace-warmed air and puts it directly into the A/C vent system, only what rises up from the floor vents.

[RyRoRyan]

As Rob said, the front thermostat controls the gas heat. If you read the thermostat manual if it cant maintain the heat using the heat pump, (if in heat pump mode) it will automatically switch over to gas heat and run that for a lockout period before trying elec heat again. The rear stat technically is the same setup except that it just does not have the wires hooked up to the gas so it will basically just turn off the heat pump if it cant maintain the temp. Since the overhead registers run the entire length of the coach, both systems will supply all the vents as long as the registers are closed at the actual units. I have found that I normally dont need both heat pumps running to keep the unit warm. And if it goes down in the mid 30's if one pump stops working then the other one is going to stop real soon after. What I have noticed is that if the front stat switches to gas before the rear stat turns off the pump, then the gas system will keep the coach warm and the rear stat will never see the drop in heat to turn the heat pump off. When this happens, the heat pumps fan will come on, but blow cold air and the front stat will turn the gas on and the systems will in a way fight with each other. It will maintain heat, but you will use way more gas with it trying to fight with the cold air coming in from the heat pump. To prevent this, I just leave the rear unit off if I know that it is going to get really cold out that night. It also helps with noise while sleeping, as the rear unit is just over the bed will not run.

[Mwade]

Thanks guys, good info!