Thermostats often come with an emergency heat setting, which can confuse homeowners. This setting is usually activated during emergencies, like when the heat pump breaks down or if the outside temperature is extremely cold for the heat pump to handle.
This blog will explain how emergency heat works on heat pumps and the necessity of this setting.
What is a Heat Pump?
A heat pump is an electric-powered unit that extracts warmth from the outside air during the winter months. The hot air that gets circulated inside the house helps in keeping it warm. Although the warm air is extracted from the outdoors, there is still a need for auxiliary sources if the weather gets too cold outside.
This indicates that the heat pump will be insufficient for heating, and it may need the support of electric heat coils or a fossil fuel furnace. This is the reason why heat pumps are available in two parts. One unit inside the home pulls heat from a furnace or electric coil, and another unit outside draws heat from the air outside.
What is Emergency Heat on a Heat Pump?
Since a heat pump cannot extract enough warmth from outside air during extreme cold weather, it is important to have a secondary heating source like emergency heat.
This setting is often used to give the heat pump a break and prevent system damage. It also effectively keeps the home warm when the temperature is below freezing.
The “em heat” setting on the thermostat shows that the emergency heat has been turned on, and it will keep functioning until turned off manually.
How Does Emergency Heat Work?
When emergency heat is activated, the compressor and heat pump turn off. The backup system then takes over, and this process keeps the house warm without putting stress on the outdoor heat pump.
Although emergency heat is mostly electric, it can also run on natural gas or oil. If the emergency heat is manually set on the thermostat, the system skips the heat pump. This makes it draw heat directly from either the electric heat strip or the gas or oil furnace. For electric systems, the air handler works as an electric furnace.
Sometimes outdoor temperatures reach 40 degrees or higher, and the home still cannot stay warm without emergency heat. In this case, it is better to contact an HVAC service provider, because the heat pump may have frozen or need repair.
When to Use Em Heat?
Below are the situations when one should turn on the setting manually:
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If the outside temperature drops very low, it makes it difficult for the heat pump to warm your home.
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If the heat pump turns off due to severe cold or an ice storm.
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Debris or a fallen branch has damaged the heat pump.
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If a homeowner is waiting for an HVAC service provider to arrive and repair the unit.
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The unit is in the process of thawing out.
Why Should Em Heat Be Only Used During Emergencies?
Emergency Heat can get less efficient because it bypasses the primary heat pump and relies solely on the auxiliary or secondary heating system. This means that the em heat does not use both systems together when the temperature is below 35°F.
If the heat pump stops working, then there is always a chance that homeowners turn em heat on to circulate heat in the house. This process is not cost-effective and can increase the cost of heating, thereby straining the heating and cooling system. It is best to contact a licensed HVAC company right away to fix the issue.
If required, the heat pump will always activate the secondary heating. Therefore, it is recommended for homeowners to keep the em heat switched off. Make sure to turn it off if switched on accidentally.
Is Em Heat the Same as Auxiliary Heat?
Thermostats also have the option called “aux heat”. This function is automatic and turns on if the temperature falls below a certain level and the indoor temperature drops 2℉ to 3℉ below the thermostat setting.
This setting operates supplemental heating for hours through an electric heat strip. However, this will not work if there is a frozen heat pump.
Is Em Heat Costly?
One popular misconception is that emergency heat quickly heats the home. However, the home in fact heats up at a much slower rate due to its constant reliance on gas or electricity.
This setting typically consumes 2 to 3 times more gas or electricity than a standard heating and cooling system. As a result, bills tend to be 2 to 3 times higher.
Conclusion
Understanding how emergency heat works often helps homeowners make better decisions about when and how to use it. The best approach is to allow the heat pump to operate normally and save the emergency heat for real emergencies. This way, heating bills remain reasonable, and the equipment lasts longer.
