EM Heat On Honeywell Thermostat: How And When To Use?

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I have been using a Honeywell Thermostat in my house for quite some time. It keeps my house warm on moderately cold days.

To make the most out of my thermostat, I’ve been researching all its niche features, like EM Heat. I’ve gone through countless articles online to find out the best time and the best way to use it.

EM heat on the Honeywell Thermostat stands for Emergency heat, which switches the thermostat from primary mode to auxiliary mode. It utilizes a backup electric heat strip or gas furnace to heat up the room.

Modes of Your Heat Pump

There are three modes in which a heat pump works. Depending on the climate, the heat pump will switch to different modes automatically.

Primary heat pump

This is the normal mode of operation for a heat pump. In this mode, the heat pump sucks in air from the house’s exterior and uses it to heat the interior.

This operation is similar to that of an ordinary air conditioner.

Similarly, the heat pump sucks out the hot air inside a room and expels it outside to cool the room. This mode of operation is ideal for climates when the outside air is sufficiently warm.

Auxiliary heating

If the temperature outside your room is too cold, your heat pump won’t be able to pull in enough hot air to warm the room. In this case, the heat pump switches to auxiliary heating mode.

The heat pump consists of an electric heat strip, which heats up when electricity is passed. This heat is used to warm the room. In auxiliary mode, the heat strip is turned on to provide additional heating.

Operation in this mode will increase the electricity bill considerably. So you should limit the use of the thermostat in this mode as much as possible.

Backup furnace

This mode is an alternative for auxiliary heating using electricity. A gas furnace is utilized to provide the required heating to the room. The heat generated by burning gas is distributed in the room.

This mode of operation is preferred to electric mode since gas is cheaper and, at the same time, quite effective in heating the room.

What is EM Heat?

EM heat stands for Emergency heat. When the EM Heat is switched on in a Honeywell Thermostat, the heat pump switches its operation from primary mode to auxiliary mode completely.

This means that instead of the conventional method of pulling warm air from outside your house, the thermostat turns to a backup electric heat strip or a gas furnace for heating the room.

Simply put, EM Heat indicates operating solely in the auxiliary mode. You must ensure that the EM Heat should be switched on only when the outside temperature falls too low.

Otherwise, the cost of operation, particularly in the case of the electric heat strip, will rise significantly. EM Heat enables your thermostat to moderate the temperature of your house all year round in any climate.

Warning Against Switching to EM Heat Manually

Heat pumps automatically switch between different modes depending on the climate outside the house. So if the temperature drops too much, you don’t have to lift a finger.

Your heat pump will take care of the extra heating on its own. Similarly, if the temperature becomes moderate, your heat pump will switch back to primary mode.

Manual switching to EM Heat is not recommended. If you manually switch on EM Heat, the heat pump will switch to auxiliary mode completely.

It won’t go back to primary mode even if the temperature becomes normal until you manually switch it back.

If you forget to switch off EM Heat mode, the heat pump will simply waste your money by continuing in auxiliary mode, even during a moderate climate.

So it is best to leave the switching to your Honeywell thermostat.

When to Use EM Heat

The need for EM Heat usually arises in the winter, when the outside temperature may fall too low. In such extreme conditions, your heat pump will switch to auxiliary mode to provide extra heating.

You may use electric heat strips or gas furnaces to provide this extra heat. Using electric heat strips will be quite expensive, so preferably you should use gas furnaces.

Once the outside temperature rises, EM heat will be switched off by the heat pump automatically.

Features of EM Heat

The efficiency of EM Heat mode exceeds the normal heat pump mode by miles. EM Heat mode can heat the air to very high temperatures and can operate even in very cold temperatures.

The cost of using a thermostat in EM Heat mode for prolonged periods is very high. Therefore, you should limit its use to situations where the cold is unbearable and for short durations.

In cases when the heat pump becomes damaged or faulty, you can switch to EM Heat mode.

But, it would be best if you repaired the heat pump as soon as possible since EM Heat mode operation is pricey.

In Case of Emergency

The name itself suggests that you should use EM Heat only in case of emergencies.

In days of extreme cold, the primary mode of operation of heat pumps won’t be adequate to keep the interiors of your house warm. In such cases, EM Heat is your only option to heat your house.

Other examples of emergencies are when the heat pump is damaged and needs repair or when the heat pump has been frozen due to the extreme cold.

These situations leave you with no other option but to rely on the auxiliary sources of heat, namely electric heat coils and gas furnaces.

So you can run the heat pump in this mode till the repairs have been made.

Cost

Use of EM Heat comes at a hefty price. Since an ordinary Honeywell Thermostat simply sucks in warm air from outside to heat your house, its operation doesn’t cost much.

But when EM Heat is switched on, you rely solely on external energy sources such as electricity, gas, oil, etc.

These energy sources cost too much, especially electricity. This is the reason why you should use EM Heat only in emergency cases.

How to Know if EM Heat is Active

If EM Heat is switched on in your Honeywell Thermostat, It will be indicated by a red light indicator on the heat pump.

So if your heat pump is operating in auxiliary mode when you don’t need it, you can recognize it with this red light and switch it off immediately.

If the EM Heat mode is switched on by accident, this light will let you know and thus, help save a lot of money.

Final Thoughts

And with that, you have learnt everything you need to know about using a thermostat in EM Heat mode.

You now know what it is, what it does, how to use it, and how to know when it’s in use.

If you decide to set up a Honeywell thermostat in your home, make sure you opt for a gas furnace as your auxiliary heat source.

Do not forget to check the indicator light from time to time to ensure that the EM Heat mode is not switched on by mistake.

You can perform routine servicing of the thermostat to avoid malfunctions and ensure proper operation in both normal mode and EM Heat mode. And that settles it!

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Frequently Asked Questions

When should I put my thermostat on in emergency heat?

The thermostat automatically switches on emergency heat when the outside air becomes too cold for the heat pump in the thermostat cannot pump adequate amounts of hot air into the house.

Once the outside air becomes warmer, the thermostat automatically switches off emergency heat.

What’s the difference between heat and EM heat on my thermostat?

In any thermostat, heat refers to the normal mode of operation where warm air is sucked from outside and distributed inside a house for heating.

EM heat refers to the second or auxiliary mode of operation where the thermostat produces heat using an electric heat coil or gas furnace to heat air and circulate it in the house.

This mode is used when the outside air is too cold for the thermostat to heat the house.

Does auxiliary heat come on automatically?

Depending on the temperature outside your house, the thermostat automatically switches on the EM Heat.

When the temperature becomes normal in the same fashion, you will switch off the EM Heat automatically.