Why does my PTHP. shut off and switch to electric resistance heat?
im guessing its there way of defrosting the coils , as with this type (small) its tough to defrost the coils in an efficient way , hp runs normal to within one or two degrees of setpoint , hp shuts off or reverses in low speed , back up heat comes on to complete the room heat and to generate the heat needed to defrost the coils , entire unit shuts off when set point is reached , reversing valves set for heat and wait till next cycle
now mine does something slightly different : it runs for fifteen minutes and if set point is not reached it switches to back up and reverses the coils ,leaves compressor on (low speed) , this heats the coils up and defrosts the outdoor unit , and if it runs long enough twenty minutes total time , it goes back to normal and aux heat shuts off . this drives me insane thinking how much im spending on heating the outside !! but im sure its needed to prevent ice build up on outdoor coils ,and I sure don't want that cracking with ice formations
on Jan 30, 2016