Gas and Oil Home Heating Furnaces - Furnace Operation

My furnace is a heat pump, Janitrol Mod A42-20. From my first post and investigating causes, i discovered it has a relay for the "Emergency" back up. How does this operate? is it sensitive to the outside temp? I have never seen it light the light on the thermostat unless i switch it to Emergency at the thermostat. Should i doo that or just let it do its thing??

Thanks Again for the fix on my first post, great bunch of people here!!

Randyh

If your HP compressor craps out,or your outdoor fan motor quits,if your out door unit has 6 inches of frost on it you have a backup.The relay is energized by your tstat to provide you with heat until repairs can be made.Your emergency heat brings on electrical heat.What else does this relay do?When your outdoor unit senses frost buildup,it has to remove it.Your unit switches to A/C to remove the frost!!!Going to get cold in your house with A/C running?Nope this relay also brings on electric to to temper the air!!!!Your most efficient means (cost less too) is the HP compressor.If your compressor or other component quits a degree or 2 coolder the tstat will bring on your emergency heat.Thereare a lot of varities about outside air controls.Basically they sense the outside air and bring on your emergency or backup heat at a desired temp..Usually when the heat pump can no longer extract heat efficiently from the outside air.Hope I have shed some light on the every mystical HP operation!!!!!PDF

Assuming you have a janitrol heat pump t'stat... The blue light will only come on when you physically switch to emergancy heat. It senses no outdoor temperatures. It switches off your heat pump and heats with only your resistive/aux/2nd stage heat. If you are not having problems with your heat pump keeping temperature leave it off.

Is there a magic temperature that would be better to turn it to Emergency??

Thanks,
Randy

If you set your tstat to 72 and the HP can't keep up,room temp drops to 70 ,the emergency heat will assist the heat pump.However if you see that the outdoor unit is frozen and won't defrost you should switch to "E" heat.York and CARRIER HP's have an outdoor sensor that will keep electric heat off for more efficient operation.PDF