One of the most common questions we get about heat pumps (and geo-thermal systems) is related to one setting on the thermostat. Many homeowners ask “when do I use Emergency on my heat pump?”
The answer is almost never, and this article will help you understand why.
A common misconception is that heat pumps don’t work in cold weather, so the Emergency Heat setting is put on there to use anytime it is really cold outside. The recent Arctic cold blast we had provided an opportunity for people to try out the emergency setting, and many homeowners did. We spoke to people who tried it and then didn’t understand why the temperature in their house continued to slide down, and why that setting didn’t solve their problem.
Some homeowners have learned from past mistakes and don’t want themselves or others to continue to make them. On the image above, you can see that this older homeowner even added a sticky-tape sign to his thermostat as a memory aid to avoid using that setting.
How a Heat Pump works
A heat pump is a mechanical system that extracts heat from one place and transfers it to another place that is colder, which raises the temperature there. In the winter, it brings heat into the house, and in the summer it takes heat out of the house, but it uses the same process. A heat pump can transfer 3 to 4 times as much heat as what would have been produced by the amount of electricity it consumes, so they are often described as being 300%-400% efficient.
A furnace or boiler burns fuel or uses electricity to produce heat, and an air conditioner uses refrigerant to remove heat, so an HVAC system uses two different processes. Many high-efficiency furnaces are in the 90-98% range, so heat pumps produce much better performance for the cost.
Heat Pumps that are located in regions where snow and ice normally occur need some kind of supplemental heat system to boost their heat output during very cold periods of time. For electric heat pump systems, electric resistance heating normally does the output boosting. For non-electric heat pump systems, natural gas, fuel oil, or a boiler normally provide the supplemental heat.
Remember this important point: you do not need to turn on the supplemental heat. The heat pump will turn it on automatically when it can’t keep up with heat demand by itself. As long as the switch is set to the “HEAT” position, the heating system will use both sources of heat to meet the set point you have put into your thermostat. You don’t have to do anything on a cold day, just leave the setting where it normally is.
What does the Emergency Setting Do?
When you change the thermostat to “Emergency Heat”, the heat pump will be prevented from functioning normally, and only the supplemental system will run. Since that part of the system is not sized to heat the whole house by itself, the supplemental heat will probably not bring the house to the desired temperature. On a cold day, the supplemental system will continue to run and it will consume a lot of electricity or fuel, but your home will get colder and colder because you have lost the main source of heat, along with the 300-400% efficiency you were getting.
When do I use Emergency?
Almost never – most homeowners will never use it. It was designed to be used when a mechanical problem occurs with the the heat pump and repairs are needed. For example, if a large tree limb fell and damaged your external heat pump, or if a mechanical problem caused the pump to freeze itself solid, you could use the Emergency Heat to give you some warmth for a little while. If it occurred on a mild day and you had an electric system, that source of heat might be enough to help for a few hours until a repair person could get there. Remember – unless you have a situation like one of these examples, do not use the Emergency Heat setting.
If this explanation wasn’t complete enough, or if you still have questions about your heat pump, give us a call or send in a contact form to Ask the Experts. We’ll be glad to talk to you and help you understand your system.
Be Wiser — Call Kaiser!