It can, depending on what type of t-stat is being used.Most heat pump stats that I know of, will have a w1 and a w2, which represents 1st stage heat, and 2nd stage heat. Many times, there is 1-3 degrees difference between 1st and second. If the house temp is say 66, and the stat was set at 68, the t-stat will say "we're not keeping up", and bring on 2nd stage heat.Many times, the back up source is electric elements, and can be configured to run both the compressor, and elements. But in this case, with propane back-up,the gas fired possibly cannot run, with the compressor, if the "a-coil" is downstream from the furnace. The high freon pressures(created from the "furnace" running) could damage the system.
Hey Rob, I'm going to assume that since you know the outside temp., that you possibly have a Honeywell touchscreen t-stat, or a White Rodgers touch screen? If you have a touchscreen stat that shows the outside temp,there's a good possibility that your t-stat will shut the heat pump off at a given outside temp. Let me know if you are using this type of stat, and I will walk you through this feature. It may seem confusing at first, but will come crystal clear.
