HVAC in Emergency Heat
Table of Contents
Overview
Occasionally, a thermostat may display “Emergency Heat” or “Auxiliary Heat.” When customers see this, they may believe something is wrong with their HVAC system. In many cases, this is normal behavior—especially for heat pump systems—but it can also indicate a configuration issue at the thermostat.
- The unit will switch to Auxiliary Heat providing supplementary heat to work along with the heat pump.
- The unit will switch to Emergency Heat providing supplementary heat to work instead of the heat pump.
What Is Emergency Heat?
In heat pump systems, Emergency Heat refers to supplemental heating that activates when the system needs help reaching the desired temperature.
This supplemental heat may come from:
- Electric heat strips
- Auxiliary heat, gas or electric
This does not necessarily mean the primary heat source has failed. Some units automatically disable the heat pump at very low temperatures. The heat pump may enter a defrost cycle where the pump is unavailable to provide heat during this cycle. The unit is choosing this mode to continue the heating process.
The customer also may choose to configure the HVAC mode to emergency heating during winter months. Follow the setpoint policies when temporarily or permanently editing the HVAC mode.
If a heat pump enters Emergency Heat, it can also mean that something is wrong with the HVAC unit itself and will need further diagnostics by an HVAC technician. Possible issues with the unit:
- The heat pump can’t keep up
- The compressor failed
- The system is locked out
Common Customer Complaint
A customer may report:
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The thermostat display shows “Emergency Heat.”
- This status may come after a local or remote override.
- The heating stage continues running even though cooling is needed, or the system appears to be heating unexpectedly.
In some cases, this can occur when the thermostat is configured for a heat pump when the unit is a standard system.
How to Identify Emergency Heat
Use the following indicators to determine if a system is operating in Emergency Heat mode.
Thermostat Display
Check the thermostat screen.
If it displays:
- Emergency Heat
- Auxiliary Heat
The system may be operating in a supplemental heating mode.
HVAC System Status
In the HVAC status section of EMS platform:
- Verify whether the system is calling for heating.
- Emergency heat mode may activate when the primary heating source is unable to quickly meet the heating demand.
- There may be health alerts on the units.
Temperature Readings
Monitor the supply air temperature.
- Emergency heat sources can produce very hot air.
- Supply air temperatures above ~150°F may indicate electric heat strips or other supplemental heat sources are active.
Override Status
Some systems allow manual overrides.
Check whether:
- The system has been manually set to Emergency Heat.
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Check the configuration to see if it has been configured to Emergency Heat.
- Configuration Module/ Schedule/ HVAC/ HVAC Mode
Platform Verification
If using GridPoint’s GEM platform, you can review:
- Real-time HVAC mode
- Heating calls
- Temperature data
This information can help confirm whether the system is actively using supplemental heating.
Possible Explanation: Thermostat Configuration
Our thermostats include dip switches that define the HVAC equipment type.
If the Heat Pump setting is enabled, the thermostat may attempt to control auxiliary or emergency heat stages.
Solution
Check the thermostat’s dip switch configuration:
- Locate the Heat Pump configuration section on the thermostat.
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If the connected HVAC equipment is not a heat pump, switch the setting to Standard Unit.
- Confirm dipswitches in Commissioning Paperwork
- After adjusting the configuration, verify the system operation.
**Did you know you can ask Knowledge Base AI to decode dipswitches? Try it out!
Best Practices for Troubleshooting
Scenario where the unit should be heating because the zone is cold but the unit is in emergency heat mode.
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Check whether the thermostat is configured as a heat pump or standard unit.
- Check commissioning paperwork to determine the correct dipswitch settings.
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Confirm HVAC configurations to ensure emergency heat was not set intentionally.
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If configurations are set to emergency heat, be sure to follow the site’s set point policy when making changes.
- If changes are made, run heat test to ensure unit behaves as intended.
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If configurations are set to emergency heat, be sure to follow the site’s set point policy when making changes.
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Review HVAC status and temperature readings.
- Historical data regarding temperature behaviors could be viewed in the Graph data.
- We can explain what the unit is trying to do with the emergency heat but suggest that they have the unit serviced by an HVAC technician.
Scenario where the unit should not be heating and is in emergency heat mode.
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Review HVAC status and temperature readings.
- Historical data regarding temperature behaviors could be viewed in the Graph data.
- Is the zone temperature accurately represented? If not, the thermostat or ZSM may need further troubleshooting and possibly replaced.
- Verify that no manual override is active.
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Check whether the system is configured as a heat pump or standard unit.
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Check commissioning paperwork to determine the correct settings.
- It is possible the dipswitches are reconfigured seasonally
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Check commissioning paperwork to determine the correct settings.
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Verify GEM configurations of unit settings.
- Be sure to follow the site’s set point policy when temporarily or permanently updating the configurations.
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A temporary resolution could be updating the configuration of the HVAC setting to be cool only.
- Note that this is only a temporary resolution to get the unit to stop reverting to heating. This should be clearly noted for future troubleshooting to be adjusted back when HVAC issue is resolved.
- If it is a warm weather scenario where it should not be heating at all, we may need to update the Fan mode to ‘Off’ to stop it from circulating hot air.
If additional assistance is needed, consult the HVAC Health Guide or contact the response operations team.