Quick Answer
EM heat stands for emergency heat, a mode that bypasses the standard heating system to provide immediate warmth. This setting applies to homes with heat pumps or multi-stage furnaces when the primary system cannot meet the temperature demand. Check your thermostat display for a flashing light or an EM alert to confirm the status.
In this guide, Green Writer walks through how to identify what is em heat on a thermostat and how to manage it. A thermostat acts as the control hub for your home climate, but emergency mode creates a high-cost surge in energy consumption because it uses inefficient electric resistance coils instead of a standard heat pump.
A heat pump is a cooling and heating system that moves heat from one place to another. While most people assume emergency heat is a permanent fix for a cold house, you can control your home temperature to avoid using it regularly and increasing your monthly utility bill.
Emergency heat uses your backup heating system
Emergency heat is a backup heating mode that bypasses your primary heat pump. It activates your home's secondary heating source, such as electric heat strips, to provide warmth. Knowing this helps you understand why your electricity bill might increase when this mode is active.
Defining EM heat on a thermostat
EM heat on a thermostat stands for emergency heat. This setting tells the system to bypass the heat pump and use electric resistance strips to generate warmth. You should use this mode only when the heat pump fails or when outdoor temperatures drop below the system’s functional limit.
Role of the reversing valve
Users often find an emergency heat thermostat option when their equipment cannot move heat efficiently. A heat pump relies on a reversing valve to switch the flow of refrigerant between heating and cooling cycles. A reversing valve is a component in a heat pump that switches the direction of the refrigerant flow.
If this reversing valve fails or if the outdoor unit freezes, the system cannot produce heat normally. In these cases, the emergency heat setting on thermostat controls provides a backup.
Verifying setup with wiring
To confirm your situation, check if your heat pump is running but the house remains cold. A sensi smart thermostat emergency heat setup or a sensi thermostat emergency heat configuration will engage the backup strips. You can verify your specific setup by checking the wiring for a dedicated heat wire.
What does EM heat actually mean?
EM heat means the system ignores the heat pump compressor and uses electric coils. These coils act like a toaster to heat the air. This mode consumes more electricity than standard heat pump operation.
When should I switch to emergency heat?
You switch to emergency heat when a heat pump fails to maintain the desired temperature during extreme cold. This setting activates the auxiliary heat to provide warmth. Auxiliary heat uses electric resistance strips or gas to generate heat when the primary system cannot keep up.
Monitor the indoor temperature to determine if the system requires a manual change. You can identify systems that use a 2 wire thermostat and use the device on emergency heat during severe weather events or when the heat pump shuts down to prevent coil icing.
Nest thermostat navigation steps
- Open the Nest app or use the thermostat interface to access the settings menu.
- Select the heating options to locate the heat pump configuration.
- Toggle the auxiliary heat setting to the active position.
- Verify that the system shows a status change to the secondary heat source.
- Check the thermostat on emergency heat to confirm the unit is running.
Finding the emergency heat setting on a Nest thermostat
Navigate to the Settings menu on the device. Select the Heating menu to find the heat pump settings. Choose the auxiliary heat option to activate the backup system.
System behavior during emergency heat
When you turn on emergency heat, the system bypasses the heat pump and uses electric heat strips to warm the home. This mode keeps the reversing valve in the cooling position to prevent the compressor from freezing. The thermostat with emergency heat functions as a backup during extreme cold.
Activation of electric heat strips
The reversing valve directs the flow of refrigerant. In emergency mode, the system stops using the outdoor unit for heat. Instead, the indoor unit activates electric heat strips to build warmth quickly. This setup relies on the electrical wiring to power the heating elements directly.
How to enable emergency heat on a Sensi smart thermostat?
To activate this setting on a sensi smart thermostat, open the Sensi app and navigate to the device settings. Select the heat source options and toggle the emergency heat switch to the on position. The system will then prioritize the heat strips over the standard heat pump cycle.
How does emergency heat differ from regular heat pump operation?
Emergency heat differs from regular heat pump operation because it bypasses the heat pump cycle to use electric resistance coils. A heat pump moves heat from outdoors to indoors. Emergency heat generates heat directly through electricity. This mode works when outdoor temperatures drop too low to see how a smart thermostat works efficiently.
Difference between internal and outdoor heating
The reversing valve directs the flow of refrigerant within a heat pump. During regular operation, this valve allows the system to move heat. Emergency heat ignores the reversing valve and the outdoor unit entirely. It relies on internal heating elements to maintain the set temperature.
WIFI thermostat troubleshooting steps
| Operation Mode | Heat Source | Power Source |
|---|---|---|
| Heat Pump Mode | Outdoor unit heat | Compressor electricity |
| Emergency Heat | Internal electric coils | Resistance electricity |
| Backup Heating | Auxiliary heat source | Secondary power |
Why is my WIFI thermostat stuck on emergency heat
A wifi thermostat stays on emergency heat if the outdoor temperature falls below the system’s threshold. The thermostat detects this drop and switches the system to electric resistance. The unit remains in this state until the outdoor temperature rises enough for the heat pump to resume operation.
Risks of leaving the smart thermostat on EM heat
You should not leave a thermostat on emergency heat indefinitely. This mode uses auxiliary heat to provide warmth when the primary system fails. Before installing, compare in-slab and room air probes as auxiliary heat systems often rely on electric resistance coils which consume significant power to generate heat quickly.
Risks of frequent system cycling
A thermostat with emergency heat setting activates these backup components to maintain indoor temperatures. Users should only toggle this setting during a mechanical failure of the furnace or heat pump. Constant use of this mode can cause the system to cycle frequently. Frequent cycling may wear down electrical components or trip circuit breakers in the home.
Electricity costs of running emergency heat
Running emergency heat generates high electricity costs because electric resistance heat is less efficient than gas or oil. The electricity usage grows rapidly when the thermostat stays in this mode for extended periods. Users should reset the thermostat to its standard heating mode once the primary system functions again.
Manage your thermostat settings and emergency heat usage
Deciding whether to activate emergency heat depends on your current home temperature and the specific functionality of your heating system.
Thermostat configuration checklist
- Locate your thermostat's manual or installation guide. Find the physical booklet or a digital copy provided by the manufacturer. Confirm it contains a section on EM heat or emergency mode.
- Verify the current indoor temperature. Check the reading on your thermostat display. Note if the temperature is significantly lower than your desired comfort level.
- Identify your primary heating source status. Check if your main furnace or boiler is running. If the main system is off but the house is cold, proceed to the next step.
- Consult a heating technician about your specific model. Call a professional to ask if your unit supports EM heat. They will confirm if your hardware is compatible with this specific setting.
- Toggle the EM heat setting on your thermostat. Switch the mode to EM heat if your primary system is failing. Confirm the heat kicks on immediately to provide temporary warmth.
Frequently asked questions
- Why is my wifi thermostat stuck on emergency heat?
- Wifi thermostats stay on emergency heat when outdoor temperatures drop below the system’s threshold. The unit detects this drop and switches to electric resistance to maintain warmth. The system stays in this state until the outdoor temperature rises enough for the heat pump to resume.
- What does em heat actually mean?
- EM heat means the system ignores the heat pump compressor and uses electric coils. These coils act like a toaster to heat the air. This mode consumes more electricity than standard heat pump operation.
- How does emergency heat differ from regular heat pump operation?
- Emergency heat in thermostat settings bypasses the heat pump cycle to use electric resistance coils. A heat pump moves heat from outdoors to indoors. This backup mode generates heat directly through electricity instead of moving it.
- What are the electricity costs of running emergency heat?
- Running emergency heat generates high electricity costs because electric resistance heat is less efficient than gas or oil. Electricity usage grows rapidly when the thermostat stays in this mode for extended periods. Reset the thermostat to standard heating mode once the primary system functions.