Trane XR-13 with a XR402 Dual Fuel Thermostat

[gremel]

I was wandering if any of you know what is a good setting.. (comfort-wise).. to have the gas furnace come on and what would be the other setting point to have it switch back to heat-pump for heating purposes.

I believe the installer set the gas furnace temp point to come on at 35deg and the heat-pump setting to activate at 44 deg. thereby shuting off the gas furnace and using the heat-pump once again for heating purposes.

Anybody have any ideas?

Regards & thanks if you do..

jack

[wyounger]

It varies from house to house. We can't really tell you what the number will be. Typically it's between 25 and 40, but there are some exceptional cases.

There's no harm in bumping it down a few degrees at a time until you don't like the results, then backing off a bit. If you go too far, you may see one or more of the following symptoms:
1. The system will take forever to gain temperature after a setback period (though you shouldn't be doing much of that on a dual fuel or heat pump system) or when you increase the setpoint manually
2. When outdoor temp is just above your current balance point temperature and the system is running the heat pump, the system can't quite maintain your thermostat setting.
3. When outdoor temp is just above your current balance point temperature and the system is running the heat pump, the airflow out of the system may not be hot enough to avoid feeling uncomfortably drafty.

In your area, the economics of the two energy sources say you should try to get everything out of the heat pump you can and minimize use of the furnace. So basically the answer is to do that as best you can without sacrificing comfort.

[BobbyBJr]

Hey Gremel,
I see you are in Spartanburg, SC which is where I am located also. We do alot of dual fuel and I generally set the switchover point of the system a couple of degrees above the balance point. Most of the houses I have figured lately have had a balance point around 30 degrees and I have been setting the switchover point 30 to 35. Mine in my own house is set to switchover at 32 degrees and it works very well, but like wyounger said, it does vary somewhat from house to house and it don't hurt to experiment with it a little.

Bobby