Heat Pump/Furnace Operation Solitude 380-FL

[Hackers 380-FL]

I have a Solitude 380-FL with a heat pump and wall thermostat. When I first turn on the thermostat to "Electric Heat" (heat pump) after travel and the temperature in the coach is low, the thermostat reads gas/electric. When the temperature reaches a normal temperature, gas turns off.
I am currently in central Virginia with overnight temperatures that have been reaching below 32 degrees. I know the heat pump is supposed to automatically shut down (per operating instructions) when temps reach near or below freezing.
1. Should the heater automatically change over to the gas furnace or
2. Should I manually switch to the gas furnace when temps reach the mid 30's to avoid the heat pump from shutting off?

Note: Moved thread from "Ask Grand Design" channel to "HVAC" channel as the members here have answered the question. -Moderator Howard

[drifterranch]

The manufacture suggest not using the heat pump below 45 degrees and run the furnace. The heat pump becomes less effective a lower temps. There is a much longer explanation as to how the heat pump works, and will eventually lock itself out for 1:45 minutes if it cannot sustain the set temperature. I hope this helps.

[boyscout]

I have a Solitude 380-FL with a heat pump and wall thermostat. When I first turn on the thermostat to "Electric Heat" (heat pump) after travel and the temperature in the coach is low, the thermostat reads gas/electric. When the temperature reaches a normal temperature, gas turns off. I am currently in central Virginia with overnight temperatures that have been reaching below 32 degrees. I know the heat pump is supposed to automatically shut down (per operating instructions) when temps reach near or below freezing. 1. Should the heater automatically change over to the gas furnace or 2. Should I manually switch to the gas furnace when temps reach the mid 30's to avoid the heat pump from shutting off?

drifterranch has advised you of the manufacturer's recommendation but it's more than that. The thermostat WON'T trigger the heat pump when the ambient temp is in the low 40s. Wouldn't do you much good if it did as drifterranch said, but the reason it's not trying for you is because that's the way it's designed.

Your thermostat may differ from ours - we have the Airxcel 96XX - since I've never seen it say "gas/electric". On ours, if set to Heat ELEC when the temp is too low for the heat pump it just ignores the instruction and the gas furnace starts up even though the t-stat continues to show the Heat ELEC setting.

[Hackers 380-FL]

Thanks to both of you. I kind of figured that setting the thermostat manually to gas furnace was the way to go but the owner's manual stated mid 30's (yes, I am one that reads owner's manuals... LOL). I have been noticing that anything above 40 degrees it works real good. But when the outdoor temps go below 40, that is when it starts to blow out cool air. I do not plan to be in these colder climates much longer. We wanted to spend some time through Christmas with the family in Eastern Pennsylvania, so here we are, using a bunch of propane and the Solitude is keeping us warm anyway. Furnace it will be when the outdoor temps hit >40 <45!

[LDJohnson]

We have a similar situation, however I can’t get the gas pump to kick on when I select Gas. We keep the RV in a Fully enclosed shop so the temperatures are around 55 and we like to keep it around 60. I can get the heat pump on with the electric setting. However I cannot get the Gas Furnace to come on at all.

[howson]

We have a similar situation, however I can’t get the gas pump to kick on when I select Gas. We keep the RV in a Fully enclosed shop so the temperatures are around 55 and we like to keep it around 60. I can get the heat pump on with the electric setting. However I cannot get the Gas Furnace to come on at all.

What furnace model? When the post states, "...select Gas..." I assume that means Heat is selected on the thermostat or perhaps your thermostat is different than what I'm familiar with (what model thermostat)?

When the furnace is expected to come on, what temperature is the thermostat set at? Is there any reaction from the furnace or thermostat?

[pengle]

Hackers 380-FL
The interaction between the thermostat and heat pump and your furnace is way more complicated. I pulled this off of an RV Products website a few years ago. It IS detailed, but it may help you figure out "why is it doing that!"

The Heat Pump is an electric source for heat. It will supply and maintain heat assuming the
outside (ambient) temperature is above 40 degrees. This number of course can be slightly higher
or lower depending on the humidity. Higher humidity can cause a heat pump to lose efficiency at a
slightly higher ambient temperature, while lower humidity can cause a heat pump to lose efficiency
at a lower ambient temperature.

Since no one wants to wake up to find that the outside temperature dropped below forty degrees and
it is now 50 degrees inside the coach, the Heat Pump thermostats are programmed internally to
recognize when the temperature drops five degrees or more from the set temperature to the actual
inside room temperature. When the temperature exceeds five degrees or more between the two, the
thermostat will default to the next available heat
source.

The thermostat, upon sensing a temperature split of five degrees or more in the electric heat
mode will bring the gas heat on to assist the electric heat. This is the first strike. A strike
is created by the thermostat having to change modes (or run dual modes to sustain a temperature
split). The electric heat and the gas heat will continue to run together until the thermostat
reaches the set temperature and satisfies. When the electric heat comes back on, it will be in
electric heat only at that point. If the temperature again drops five degrees or more from the set
point, the thermostat will again bring the gas heat on to assist. This is strike two. The system
will then go through the above stated procedures. If the temp should drop five degrees from set
point for a third time, the thermostat will give up on the electric heat, lock the electric heat
out for two hours (showing either DIFF on the display or FLASHING GAS HEAT on the display) and
default to Gas heat only. You WILL NOT be able to run any Electric heat
during this two hour lockout.

This is the normal operation for these thermostats. We can also cause the thermostat to lock
out in a few ways. If we set the Electric heat set point five degrees or more higher than the
room temperature the thermostat will default the same as it would if the temperature dropped five
degrees or more. IF at any time the differential between the set temperature and actual
temperature is five degrees or more, the thermostat will go into a strike point regardless of
whether it is caused by raising the temperature too far, or the temperature falling inside the
coach.

The other way the thermostat will receive a strike is if the system runs for twenty minutes and
cannot reach the set temperature (satisfy). Again the thermostat senses that something is wrong
with the system and defaults to the next available heat source to assist. These strikes are the
same as the strikes mentioned above and any combination of three strikes will result in a two hour
lockout.

Once the system comes out of lockout, it will only require 1 strike to go back into lockout. So
keep in mind, if you are coming out of a two hour lockout, be careful to keep the set and room
temperature within four degrees otherwise you will lock the system out again.

To summarize:
1). There is no outside ambient sensor to shut down the heat pump. The heat pump will shut
down only if the system is locked out. Ambient temperature does affect the performance of
the electric heat.
2). If the thermostat set point and actual room temperature are FIVE degrees or greater the
system will default to the next heat source for assistance and obtain a strike. Three consecutive
strikes and the electric heat will be locked out for two hours.
3). If the electric heat runs for twenty minutes and cannot satisfy and shut the compressor off,
the system will also default to the next heat source for assistance and obtain a strike. Three
consecutive strikes and the electric heat will be locked out for two hours.
4). Once the thermostat is locked out, it is a hard lockout. There is no reset that will bypass
the lockout. Pulling the fuse will not reset the thermostat lockout.