E14
Google Nest Thermostat
Severity: ModerateWhat Does This Error Mean?
Nest error E14 means the auxiliary heat (backup heat) did not respond when the Nest requested it. Auxiliary heat is the backup electric resistance heating in heat pump systems that kicks in when the outdoor temperature is too cold for the heat pump to work efficiently. If this backup system does not respond, your home may not reach the set temperature on cold days. A blown fuse, a tripped breaker, a failed heating element, or a wiring issue are the typical causes.
Affected Models
- Nest Learning Thermostat (1st, 2nd, 3rd gen)
- Nest Thermostat E
- Google Nest Thermostat (2020)
Common Causes
- The electric air handler has a blown fuse for the heating element circuit
- A circuit breaker for the auxiliary heat strip has tripped
- The W2 or AUX wire from the Nest to the air handler is disconnected or not configured in Nest settings
- One of the electric heating elements inside the air handler has burned out
- The sequencer relay that controls the heating elements has failed
How to Fix It
-
Check the circuit breakers for the air handler. Electric auxiliary heat often has its own dedicated breaker (sometimes two breakers) separate from the main air handler breaker. Look for breakers labeled 'Heat Strip', 'AUX Heat', or 'Air Handler 2'. Reset any tripped breakers.
Electric heat strips draw very high amperage (30-60 amps per strip). Their breakers trip more easily than most household breakers.
-
Check the Nest equipment settings. Go to Nest Settings > Equipment and verify that auxiliary or emergency heat is configured and that the W2 or AUX/E terminal is set up correctly. If the Nest does not know you have auxiliary heat, it may not be sending the right signal.
If you recently replaced a thermostat and the installer did not configure the Nest correctly for your system type, E14 can appear because the auxiliary heat was never properly set up.
-
Check the W2 or AUX wire at both the Nest and the air handler. This wire carries the auxiliary heat command. Turn off the HVAC breaker, then verify the wire is firmly connected at both ends.
On some systems, the AUX wire goes into the same terminal as W1 through a jumper. Check your original wiring photo (if you took one) against the current configuration.
-
Test auxiliary heat manually. Put the Nest into Emergency Heat mode (go to Nest Settings > Equipment > Emergency Heat and turn it on). This bypasses the heat pump and runs only the auxiliary electric heat. If the house warms up, the auxiliary heat works but is not triggering automatically. If it does not warm up, there is a hardware problem.
Emergency Heat mode should be used only for testing or genuine heat pump failures. Running on emergency heat continuously is very expensive — electric resistance heat uses 2-3 times more electricity than a heat pump.
-
If emergency heat mode does not produce warmth, call an HVAC technician to inspect the heating elements inside the air handler. One or more elements may have burned out, or the sequencer relay that controls them may have failed.
Air handlers commonly have 2-4 heating elements wired in stages. Partial failures — where one element works but another does not — are common and reduce heating capacity without eliminating it entirely.
When to Call a Professional
Electric heating elements inside an air handler operate at 240V and high amperage. Inspection and replacement of heating elements requires a licensed HVAC technician. Do not open the air handler and touch heating element components without proper training.
Frequently Asked Questions
What is the difference between auxiliary heat and emergency heat?
Auxiliary heat turns on automatically when the heat pump alone cannot maintain the set temperature — typically when it is below 30-35°F outside. The heat pump and auxiliary heat run together to warm the home more quickly. Emergency heat bypasses the heat pump entirely and runs only the electric backup heat. Emergency heat is meant for situations where the heat pump itself is broken. Running in emergency heat mode unnecessarily is much more expensive since electric resistance heating is far less efficient than heat pump heating.
My house is cold but neither E12 nor E14 show up. What is happening?
If the house is not reaching temperature but no error codes appear, the heating system is running but not keeping up with demand. This is different from a non-responding system. Possible causes include an undersized heat pump for the climate, very cold outdoor temperatures exceeding the heat pump's design range, poor insulation in the home, or the auxiliary heat elements partially failing without a complete failure. In cold climates below 0°F, even a correctly sized system can struggle. Check that both the heat pump and auxiliary heat are running during a cold day by listening to the air handler and outdoor unit.
How do I know if I have a heat pump or a regular furnace?
The easiest way to check is to look at your outdoor unit. If you have both an outdoor unit AND the system also heats in winter, you have a heat pump. Furnaces heat using gas or oil and do not have a functional outdoor compressor unit for heating. You can also check your Nest settings — go to Equipment and see if it lists 'Heat Pump'. Heat pumps are common in mild climates (southern US, Pacific Northwest) because they are very efficient until temperatures drop below freezing.