Emergency Heat switch on a Heat Pump thermostat confuses many people. The
fact of the matter is that most people don't seem to understand exactly what
Emergency Heat is and when they need to use it. Many people think that Heat
Pumps don't work in cold weather and they are supposed to use the emergency
heat whenever it gets really cold... Wrong!
Simply put, all Heat Pumps in northern climates [below 35 degrees]
need a supplemental heating source. Usually it is in the form of electric
resistance heating. This is an all-electric Heat Pump. It can be a gas, oil,
or hot-water back-up system as well. The supplemental heat is also referred
to as "second-stage" or "back-up" heating, "first-stage" being the Heat Pump
only. The supplemental heat is also what is used as the Emergency Heat.
Different systems have different ways of
determining when the second-stage comes on to assist the heat pump but it is
always done automatically. So the two stages will work together in the
colder months and it is not necessary to switch your thermostat to Emergency
Heat. Now we know what supplemental heat is and that it is also used for
So when do
I actually use the Emergency Heat?
As the name implies, it is only used in emergency situations. It is
used when there is something wrong with first-stage heating [the Heat Pump
itself]. In other words, if you notice your house is cold and it isn't
heating properly and you went outside and noticed that a tree fell and
crushed your heat pump, that would be a good time to switch to Emergency
Or if you look at the picture below; this Heat
Pump turned into a block of ice due to a malfunction. At this point, it
isn't capable of providing any heat. Simply turn the thermostat to Emergency
Heat and call for service.
happens when I switch to Emergency Heat?
When switching to Emergency Heat, the red indicator light will go on. And it
will stay on until you stop using the Emergency Heat. This just lets you
know you are in emergency mode. On a call for heat, no signal will be sent
to the outdoor Heat Pump. Only the indoor unit and the back-up heat will
run. On all-electric systems, this will provide enough heat to keep you
going until the Heat Pump can be fixed. Gas/Oil/Hot-water system should
provide plenty of heat.