EM Heat: What is It and When to Use It?
EM Heat means Emergency Heat. On a heat-pump thermostat, Emergency Heat is a manual backup mode that turns off the heat-pump compressor and heats the home using the backup heat source instead. That backup may be electric resistance heat or, on a dual-fuel system, a furnace. This is different from Aux Heat, which a compatible thermostat can bring on automatically to help the heat pump when extra heating capacity is needed.
That’s why we’ve created this guide to help educate you on the EM heat setting and the appropriate way to use it in your home. Remember, it’s always important to understand your home appliance settings before making any changes or adjustments.
What is Emergency Heat and What is “EM Heat” on a Thermostat Setting?
“EM heat” stands for emergency heat and it’s a setting on your thermostat that controls your home’s backup heating system. If you have this setting, you probably have a heat pump and a secondary heating source, like gas, oil, electric, or hot-water.
Typically, your heat pump is the primary heating source. Depending on the thermostat, equipment and installer settings, auxiliary heat can come on automatically when the system needs help meeting the heating demand. There is no single outdoor temperature at which every heat-pump system switches to backup heat.
However, if you manually switch to EM heat, your home will only be heated by the secondary system. This can be less efficient and result in higher energy bills. Therefore, it’s important to only use this setting in emergency situations, not just for extra warmth.
EM Heat: How Does It Work?
If you own a home with a heat pump, then you likely have a two-part heating system. The primary part is the heat pump, which is usually located outside of your house, while the secondary part is the auxiliary heating source, located inside. This secondary source is designed to provide additional heat when the outside temperature is too low for the heat pump to extract heat efficiently.
Different thermostats have different methods for determining when to activate the auxiliary heating source, but it’s usually triggered automatically when temperatures fall below a certain threshold or when the heat pump needs to defrost.
Most of the time, you don’t need to manually switch to the “EM heat” setting, as your thermostat will automatically activate the secondary source as needed. However, if you do manually switch to EM heat, you’re telling your heating system to stop using the heat pump and rely solely on the auxiliary heating source. It’s important to understand how this system works so you can use it effectively and avoid unnecessary heating bills.
Should I Turn on my Emergency Heat? When Should I Use EM Heat?
Using emergency heat should only be done in emergency situations when your primary heating system has failed or is unable to provide adequate heat. It’s not meant to be used as an additional source of heat on extra cold days, as this can result in increased energy costs and a higher heating bill.
If you suspect that there may be a problem with your primary heat pump, such as it’s not working properly or it’s frozen, you can turn on your EM heat as a temporary solution until you can get it fixed. This setting is meant to serve as a backup in case of failure and should only be used in cases where your primary heating system has failed or is unable to provide heat.
In case of an emergency, it’s important to reach out to a qualified TEK Climate HVAC service technician to get your primary heating system fixed as soon as possible. Using EM heat for extended periods of time can result in inefficiencies and increased energy costs, so it’s best to use it only when necessary and for short durations.
Accidentally Turned on Emergency Heat? What Now?
If you selected EM Heat accidentally and the heat pump is working normally, return the thermostat to its normal Heat mode using the instructions for your model. If you selected EM Heat because of a fault, have a qualified TEK Climate technician assess the system.
It’s important to remember that emergency heat is meant for emergency use only and should only be used in the event that your primary heating system is not working properly. Using emergency heat as a primary source of heat can lead to increased energy bills and reduced efficiency. If you are having trouble with your heating system, it is always best to contact a qualified TEK Climate service technician to help you diagnose and fix the problem.
Heat Pump Emergency Heat: When Does a Heat Pump Switch to Emergency Heat?
A heat pump operates in its normal mode by extracting heat from the outdoor air. In normal Heat mode, the controls may call for auxiliary heat when additional capacity is needed. Emergency Heat is a manually selected backup mode; it does not automatically activate at one fixed outdoor temperature.
However, if your system frequently uses auxiliary heat even during mild weather, it may indicate a malfunction and it is advisable to call a TEK Climate technician to inspect the system. On the other hand, if you manually switch to the emergency heat mode, the system will bypass the primary heat pump and rely solely on the backup heat source for warmth. This source of emergency heat could be a gas furnace, electric heat strip, oil, or hot-water system.
It is important to note that if the emergency heat source is electric, the cost of running the system will be much higher compared to using the primary heat pump. Use EM Heat as temporary backup when the heat pump has malfunctioned, following your equipment instructions, and arrange an assessment with a qualified TEK Climate technician.
How Much More Expensive is Emergency Heat?
The cost of running emergency heat depends on the source of the emergency heat. If the emergency heat source is electric, it can be significantly more expensive than using the primary heat pump. This is because electric heating systems typically have a higher operating cost compared to other sources of heat such as gas or oil.
The exact cost difference between using the primary heat pump and emergency heat will depend on several factors such as local energy prices, the efficiency of the emergency heat source, and the amount of time that the system is in use. To get a more accurate estimate of the cost difference, it is best to consult your energy bill or speak with a TEK Climate advisor.
EM Heat vs Heat: What is the Difference?
Thermostats with EM Heat or Aux Heat settings typically use a heat pump as the main source of heating for the home. A heat pump works by taking in heat from the outside air and bringing it inside to warm the home. However, when temperatures drop too low, this method of heating becomes less effective. At that point, the secondary heating source, such as a gas furnace or electric heat strip, is triggered to provide warmth to the home.
Aux Heat may activate automatically during recovery from a larger thermostat adjustment, depending on the equipment and control settings. There is no universal three-degree trigger. EM Heat is selected manually and disables the heat-pump compressor.
Electric auxiliary heat may supplement the heat pump. In a dual-fuel system, the controls generally switch between the heat pump and the furnace. Their operation depends on the installed equipment and settings.
When the EM Heat mode is activated, however, the heat pump is no longer in use. This means that only the secondary heating system is available to provide heat to the home, which can result in higher energy bills and less efficient heating. This is because, instead of using both the primary and secondary heating systems, you are now solely relying on the secondary system.
Will Emergency Heat Defrost Heat Pump?
No, emergency heat does not defrost a heat pump. Emergency Heat runs the configured backup heat source while the heat-pump compressor is off. The defrost cycle of a heat pump is managed by a defrost control board, which operates on a timer and has a temperature sensor on the outdoor coil.
When a defrost cycle is required, the system temporarily switches to normal cool mode by changing the position of the reversing valve, which heats the outdoor coil. During this time, the electric heat strips inside will turn on to prevent cold air from being released through the vents. Once the defrost cycle is complete, the reversing valve is returned to the heating position and the strip heat is turned off.
Honeywell EM Heat: It’s Easy To Use
On a compatible Honeywell Home thermostat configured for a heat pump with backup heat, EM Heat is selected through the system-mode controls. Follow your model’s user guide; controls and available modes vary.
EM Heat mode disables the heat-pump compressor and uses the configured backup heat source. In normal heating operation, an air-source heat pump transfers heat from outdoor air into the home; it does not heat the home by bringing outdoor air inside.
The backup source may be electric resistance heat or a furnace, depending on the system. Use EM Heat temporarily for a heat-pump malfunction, rather than selecting it just to warm the house faster.
What Does EM Heat Mean: Conclusion
In conclusion, EM Heat is a manually selected backup mode on compatible heat-pump systems. It disables the heat-pump compressor and uses the backup heat source while a heat-pump malfunction is addressed.
In Emergency Heat mode, the thermostat will regulate the temperature using a secondary heating source, such as an electric heat strip, to provide heat in an emergency situation. It’s important to note that relying solely on emergency heat can result in higher heating bills and less efficient heating, so it should only be used in an emergency and as a backup to the primary heating system.
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