Emergency Heat for heat pump systems

• Heat pumps are typically located outside of the home and look like an air conditioner.
• Contrary to their name, heat pumps can provide both heating and cooling.
• If you don’t know if you have a heat pump, follow these instructions.
• Some heat pump systems include a feature called emergency heat that can be manually turned on if the primary heating system isn’t working or keeping your home warm enough.
• You shouldn’t need to use emergency heat often, typically only in very cold weather. But if you need to run it regularly, your system may need servicing from a qualified HVAC technician.
• Emergency heat and Auxiliary Heat are different types of backup heating and operate differently. Emergency heat must be turned on manually while Nest thermostats can use Auxiliary Heat automatically as needed.

• You can manually switch your heat pump’s emergency heat on or off with your Nest thermostat. You'll only find this option if your system has emergency heat.
• Running emergency heat is usually expensive and inefficient. If you find that you need to use it often, your heat pump may not be working as well as it should. Have a local HVAC technician test your system to diagnose and fix possible problems.

Emergency heat switching instructions depend on the thermostat model you have. Select your thermostat below.

Nest Thermostat and Nest Learning Thermostat (4th gen)

Home app

1. Open the Home app.
2. Touch and hold your device's tile.
3. At the top right, tap Settings Thermostat Emergency Heat.
4. Tap the switch to turn it on or off.

On your thermostat

1. Go to Settings Emergency Heat.
2. Select Continue Yesto turn it on. If Emergency Heat is already running, select Turn offor Leave on.

Nest Learning Thermostat and Thermostat E

Turn emergency heat on

1. Press the thermostat ring to bring up the Quick View menu.
2. Go to Settings Equipment.
3. Select Continuewhen the wire diagram appears.
4. Select Continuea second time when you find a summary of your system.
5. Select Emer. Heat.
6. Select Emer. Heatagain (Nest Learning Thermostat)or Turn On (Nest Thermostat E)to confirm that you’d like to turn emergency heat on.

Your Nest thermostat will use Emergency Heat to reach your set temperature as needed until you manually turn it off.

Turn Emergency Heat off

If your heat pump's emergency heat feature isn't working after you’ve finished installation, or there's no Emergency Heatoption for your Nest thermostat:

• Your system doesn’t have Emergency Heat. Go to the first section of this article for steps on how to check.
• The thermostat’s wires aren’t in the right terminal. Double check your wiring diagram and that the wires are in the correct terminal on your Nest thermostat.
• Your Nest thermostat isn’t set up right. The correct settings depend on your Nest thermostat model:
  
  Select the thermostat you have:

  Nest Learning Thermostat

  (4th gen)

  

  Nest Thermostat

  

  Nest Thermostat E

  

  Nest Learning Thermostat

  (3rd gen or earlier)

  
  

  How to tell which thermostat you have

  Nest Thermostat and Nest Learning Thermostat (4th gen)

  1. Pull off your thermostat’s display to check if there’s a wire in the StarOB terminal.
  2. Next, open the Home app.
  3. Touch and hold your device's tile.
  4. At the top right, tap Settings Thermostat.
  5. Emergency Heatshould be listed under Equipment. If it is, it will say Off or On. There should also be Emergency heat typeand Emergency heat sourcelisted under "System details."
  6. If Emergency Heatdoesn't appear ,tap on Wiring.The StarOB terminal should say Heat pumpnext to it. If it doesn’t, either you don’t have a heat pump, your thermostat is wired incorrectly, or the wires weren’t configured properly during setup.

  Nest Learning Thermostat (3rd gen or earlier)

  1. Go to Settings Equipmentfor a diagram of the wires that are connected to your thermostat. You’ll also find which function they control.
  2. If there's a wire in the Star terminal, make sure it says Emergency Heatin the thermostat’s Equipment menu.
  3. If there are no wires in the Star  terminal or O/B terminal, you either don’t have a heat pump system or your thermostat is wired incorrectly. Both of these wires are needed for emergency heat.
  4. If there are wires in the Starterminal and O/B terminal, pull of your thermostat display and make sure the wires aren't corroded, fully inserted into the terminal, and that the terminal button stays down.
  5. If the Star terminal is not set as Emergency Heat, and you’re not sure if you should have Emergency Heat, contact a local professional  for help.

  If you’re sure your system has emergency heat, double check the Star terminal's setting.

  1. Choose  Settings  from the main menu.
  2. Turn to  Equipment.
  3. Select  Continue when the wire diagram appears.
  4. Select  Continue a second time when you find a summary of your system.
  5. Choose  Wire Type.
  6. Select  E: Emergency.
  7. The  Emer. Heat option will now be available in the  Equipment menu.

  If there's no option for E: Emergency, the Nest thermostat does not detect an O/B wire. Emergency heat is only compatible with Heat Pump systems. Check to make sure that your O/B wire is fully inserted.

  Nest Thermostat E

  Check in  Settings  Equipment. You’ll find a picture of which wires are connected to your Nest thermostat and which function they control.

  • If there are no wires in the O/B terminal or W1 terminal, make sure they haven’t come unplugged. Both of these wires are needed for Emergency Heat.
  • If there's a wire in the W1 terminal, make sure it says  AUX heat.

  Note: If  Alt heat (not AUX heat) appears , your Nest Thermostat E is configured to work with a dual fuel system. You won’t find an option to use Emergency Heat, but your thermostat will automatically use alternate heat when needed.

  • If there's a wire in the O/B terminal, make sure it says  Heat Pump.