What is emergency heat - why use it?

It is the electric strip heaters that are contained in the indoor air handler. When the heat pump will no longer function due to low outside temperature the emergency heat takes over. Actually emergency heat and the second stage of heat are the same thing on most units. The emergency heat will also come on sometimes when the outdoor heat pump goes into defrost.

Letmetellu

Correct but usually the secondary heat is electric especially if there is a emergency heat switch on the thermostat. Dual fuel units gas,oil type furnaces do not use the old style thermostats with emergency heat switch because those old style thermostats are not designed for the special settings needed by a gas or oil furnace.

But anything is possible.

It could also be the clothes dryer that you disconnect the vent from and run until you get the furnace repaired...

Or the range burners and oven