Seeing AUX Heat or EM Heat on the thermostat during a cool Brevard County morning can look like a warning, but the two labels don’t signal the same condition. AUX Heat is often part of normal heat pump operation. Emergency Heat is a manual setting for a heat pump that is damaged or unable to provide heat normally.
If your home has no heat, the heat pump is damaged, or its exterior coil is encased in ice, use Emergency Heat only as a temporary measure while the system remains off and service is arranged. During ordinary cool nights, let the heat pump and thermostat manage the temperature rather than switching modes.
Emergency Heat & AUX Heat Serve Different Roles
Both modes use a secondary heat source, but they serve different purposes. The thermostat display tells you whether that source is assisting the heat pump or replacing it.
Auxiliary Heat
AUX Heat activates automatically when the thermostat needs additional power to raise the indoor temperature. Electric resistance heat strips run while the heat pump continues operating. A brief AUX Heat display during a cold spell doesn’t, by itself, mean the system has failed.
Emergency Heat
EM Heat turns the heat pump off and relies solely on the secondary heat source, commonly electric resistance heat strips. This setting is useful when the heat pump shouldn’t run, but it isn’t a routine cold-weather mode.
Thermostat controls vary by system, so displays and settings differ among homes. The operating distinction remains the same: AUX Heat assists a working heat pump, while Emergency Heat temporarily replaces it.
When Emergency Heat Is the Right Temporary Choice
Emergency Heat is appropriate when the heat pump can’t operate safely or a technician directs you to use it while a repair is pending. In Brevard County, a system fault is generally a more relevant reason to select this mode than a normal cool night.
Consider selecting Emergency Heat temporarily in these situations:
- A technician has instructed you to use it while waiting for service or a required part.
- The heat pump has failed completely and can’t heat the home.
- The exterior equipment is frozen solid, visibly damaged, or obstructed by debris and shouldn’t run until inspected.
Once the thermostat is set to Emergency Heat, the heat pump should remain off. If you’re unsure whether the equipment is safe to operate, don’t repeatedly switch between modes. Leave it in the temporary setting until the cause is diagnosed.
Don’t Use Emergency Heat During Normal Defrosting
A heat pump often develops a light layer of frost during heating operation, especially when the air is cool and damp. Its defrost cycle periodically clears the frost so the exterior coil continues transferring heat.
During a defrost cycle, you might hear the system’s sound change or notice steam around the exterior equipment. Those signs alone don’t call for Emergency Heat. Let the cycle finish, then check whether the frost has cleared.
Thick ice that remains after normal defrosting is different. A heat pump covered in ice that won’t clear presents a heat pump repair concern. A refrigerant charge issue or failed defrost component could be responsible. In that situation, switch to Emergency Heat temporarily and leave the system off until it is inspected.
Why Emergency Heat Raises Electricity Use
A heat pump normally moves heat from the outside air into your home. Electric resistance heat strips create heat directly, so running them alone uses more electricity than normal heat pump operation.
Manually selecting Emergency Heat while the system is working raises energy use without improving comfort. Prolonged reliance also increases wear on the heat strips, including the risk of element burnout.
There is no universal outdoor temperature or set number of hours that makes Emergency Heat appropriate. Equipment, thermostat setup, insulation, and the source of the problem all matter. Use the setting only as a bridge until normal heat pump operation is restored, not throughout the season.
Signs Your Heat Pump Needs Repair
An occasional AUX Heat display isn’t a diagnosis. Persistent changes in heating performance or system behavior deserve attention during Brevard County’s heating season.
Watch for these signs:
- Weak or sporadic heat from the vents.
- Unusual noises from the indoor or exterior equipment.
- Frequent starting and stopping, known as short-cycling.
- Thick ice that remains on the exterior coil.
- Utility bills that keep rising without a clear change in household energy use.
Routine heat pump maintenance twice a year gives a technician an opportunity to inspect airflow, controls, refrigerant handling, and defrost operation before minor problems become disruptive.
The practical rule is simple: Emergency Heat is a temporary setting for a disabled or unsafe heat pump, not a substitute for normal operation.
For ongoing care, our Complete Comfort Club includes yearly tune-ups, priority service, and repair discounts, while our NATE-certified HVAC technicians repair all makes and models in Brevard County. If unresolved heating, icing, noise, short-cycling, or rising bills continue, reach Dial Duron Service Co. at (321) 341-3625 for 24/7 heating service.