Error Codes¶
This document lists error codes for the NWP500 heat pump water heater.
Warning
This document describes the underlying protocol details. Most users should use the Python client library (Data Models) which handles error parsing automatically. When an error occurs, the front panel display flashes red and shows the error code. For Level 1 errors, operation continues while displaying the error.
Error Code Reference¶
Error Code |
Sub Code |
Reason |
Self-diagnostic/Action |
|---|---|---|---|
E096 |
00 |
Abnormal upper electric heater operation |
1. Check the resistance of the heating element.
2. Check the wiring of the heating element.
3. Replace the control board.
4. Replace the heating element.
5. Replace the relay.
6. Contact technical support at 1-800-519-8794.
|
E097 |
00 |
Abnormal lower electric heater operation |
1. Check the resistance of the heating element.
2. Check the wiring of the heating element.
3. Replace the control board.
4. Replace the heating element.
5. Replace the relay.
6. Contact technical support at 1-800-519-8794.
|
E326 |
00 |
Dry fire |
Refill water until all air is expelled from the outlet and water flows. |
E407 |
01 |
Abnormal hot water temperature sensor operation for lower limit |
1. Check and reconnect the wiring.
2. Check for disconnection in Service Mode.
3. If there is no wiring issue, replace the temperature sensor.
• If the tank temperature sensor is faulty, operate in a reduced capacity using the opposite heating element.
|
E407 |
02 |
Abnormal hot water temperature sensor operation for upper limit |
1. Check and reconnect the wiring.
2. Check for disconnection in Service Mode.
3. If there is no wiring issue, replace the temperature sensor.
• If the tank temperature sensor is faulty, operate in a reduced capacity using the opposite heating element.
|
E445 |
01 |
Abnormal mixing valve open |
1. Replace the mixing valve.
2. Contact technical support at 1-800-519-8794.
|
E445 |
02 |
Abnormal mixing valve close |
1. Replace the mixing valve.
2. Contact technical support at 1-800-519-8794.
|
E480 |
01 |
Abnormal tank upper temperature sensor operation for lower limit |
1. Check and reconnect the wiring.
2. Check for disconnection in Service Mode.
3. If there is no wiring issue, replace the temperature sensor.
• If the tank temperature sensor is faulty, operate in a reduced capacity using the opposite heating element.
|
E480 |
02 |
Abnormal tank upper temperature sensor operation for upper limit |
1. Check and reconnect the wiring.
2. Check for disconnection in Service Mode.
3. If there is no wiring issue, replace the temperature sensor.
• If the tank temperature sensor is faulty, operate in a reduced capacity using the opposite heating element.
|
E481 |
01 |
Abnormal tank lower temperature sensor operation for lower limit |
1. Check and reconnect the wiring.
2. Check for disconnection in Service Mode.
3. If there is no wiring issue, replace the temperature sensor.
• If the tank temperature sensor is faulty, operate in a reduced capacity using the opposite heating element.
|
E481 |
02 |
Abnormal tank lower temperature sensor operation for upper limit |
1. Check and reconnect the wiring.
2. Check for disconnection in Service Mode.
3. If there is no wiring issue, replace the temperature sensor.
• If the tank temperature sensor is faulty, operate in a reduced capacity using the opposite heating element.
|
E515 |
25 |
Upper electric heater relay fault |
1. Check and reconnect the wiring.
2. Replace the relay.
|
E515 |
26 |
Lower electric heater relay fault |
1. Check and reconnect the wiring.
2. Replace the relay.
|
E515 |
27 |
Compressor relay fault |
1. Check and reconnect the wiring.
2. Replace the relay.
|
E517 |
00 |
Abnormal DIP switch settings |
Check and reset the DIP switch configuration. |
E593 |
00 |
Abnormal panel key |
Contact technical support at 1-800-519-8794. |
E594 |
00 |
Abnormal EEPROM operation |
Contact technical support at 1-800-519-8794. |
E595 |
00 |
Abnormal power meter |
1. Check and reconnect the wiring.
2. Replace the power meter.
|
E596 |
00 |
Abnormal Wi-Fi connection |
Contact technical support at 1-800-519-8794. |
E598 |
00 |
Abnormal RTC (Real-Time Clock) |
Contact technical support at 1-800-519-8794. |
E615 |
04 |
Abnormal ADC reference voltage |
1. Check the heating element.
2. Check the thermistor.
3. Replace the control board.
|
E615 |
27 |
Abnormal ECO feedback |
1. Check the heating element.
2. Check the thermistor.
3. Replace the control board.
|
E615 |
28 |
Abnormal compressor feedback |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E615 |
29 |
Abnormal upper heating element feedback |
1. Check and reconnect the wiring.
2. Replace the heating element.
|
E615 |
30 |
Abnormal lower heating element feedback |
1. Check and reconnect the wiring.
2. Replace the heating element.
|
E781 |
00 |
Abnormal CTA-2045 communication |
1. Check and reconnect the wiring.
2. Replace the module.
|
E798 |
00 |
Abnormal shut-off valve |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E799 |
00 |
Water leak detected |
1. Check for piping leaks.
2. If there is a tank leak, replace the entire tank assembly.
|
E901 |
00 |
Abnormal ECO operation |
1. Check the heating element.
2. Check the thermistor.
3. Replace the control board.
|
E907 |
00 |
Abnormal compressor power line connection |
Check and reconnect the wiring of the compressor. |
E908 |
00 |
Abnormal compressor operation |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E909 |
01 |
Abnormal evaporator fan operation |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E910 |
01 |
Abnormal compressor’s discharge temperature sensor operation for lower limit |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E910 |
02 |
Abnormal compressor’s discharge temperature sensor operation for upper limit |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E911 |
00 |
Abnormally high compressor’s discharge temperature |
Contact technical support at 1-800-519-8794. |
E912 |
01 |
Abnormal compressor’s suction temperature sensor operation for lower limit |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E912 |
02 |
Abnormal compressor’s suction temperature sensor operation for upper limit |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E913 |
00 |
Abnormally low compressor’s suction temperature |
Contact technical support at 1-800-519-8794. |
E914 |
01 |
Abnormal evaporator temperature sensor operation for lower limit |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E914 |
02 |
Abnormal evaporator temperature sensor operation for upper limit |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E915 |
00 |
Abnormal difference of (compressor’s discharge temperature) - (compressor’s suction temperature) |
Contact technical support at 1-800-519-8794. |
E916 |
00 |
Abnormal evaporator temperature |
Contact technical support at 1-800-519-8794. |
E920 |
01 |
Abnormal ambient air temperature sensor operation for lower limit |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E920 |
02 |
Abnormal ambient air temperature sensor operation for upper limit |
1. Check and reconnect the wiring.
2. Contact technical support at 1-800-519-8794.
|
E940 |
00 |
Refrigerant line blockage |
1. Check the electronic expansion valve (EEV) operation status for seizing.
2. Contact technical support at 1-800-519-8794.
|
E990 |
00 |
Condensate overflow detected |
Check for and remove any foreign objects from the condensate tubing. |
Error Severity Levels¶
Level 1 Errors:
Level 1 errors allow the water heater to continue operating while displaying the error condition. The front panel flashes red and shows the error icon. Users can:
Press the OK button to enter error display mode
View error details in the Error History menu
Clear the error by resolving the underlying issue
Level 1 errors are automatically cleared once the problem is resolved. The system continues minimal operations to maintain safety and prevent damage.
Viewing Error History¶
The water heater stores the 10 most recent errors, with the most recent displayed at the top. To view error history:
Press and hold the Menu button for more than 5 seconds
Select “Error History”
Use Up/Down buttons to navigate the error list
Press OK to view detailed information about a specific error
Each error record includes:
Error code and sub code
Date and time of occurrence
Operating conditions when error occurred
Troubleshooting Tips¶
Temperature Sensor Errors (E407, E480, E481, E910, E912, E914, E920):
Verify sensor wiring connections are secure
Check for damaged or pinched wires
Use Service Mode to test sensor readings
Sensors operate within -4°F to 149°F (-20°C to 65°C)
System can operate with reduced capacity using opposite heating element if one tank sensor fails
Heating Element Errors (E096, E097, E615):
Verify power supply: 208-240V AC, 60Hz, 1 Phase
Check element resistance with multimeter
Inspect wiring for loose connections or damage
Element specifications: 3,755W @ 208V or 5,000W @ 240V
Verify circuit breaker is 30A rated
Compressor/Heat Pump Errors (E907, E908, E911, E913, E915, E916, E940):
Check compressor power connections
Verify proper voltage supply
Listen for unusual compressor sounds
Check refrigerant pressures (requires certified technician)
Verify evaporator fan operation
Check EEV operation and step position
Ensure adequate airflow through air intake/exhaust (Ø8”)
Communication Errors (E596, E781):
Verify WiFi signal strength (check wifiRssi in status)
For CTA-2045: Check module connection and wiring
Restart device if communication error persists
Check front panel settings menu for communication enable/disable
Water System Errors (E326, E799, E990):
E326 (Dry fire): Ensure tank is filled before operation
E799 (Water leak): Inspect all plumbing connections and tank for leaks
E990 (Condensate overflow): Clear condensate drain tubing of obstructions
When to Contact Technical Support:
Contact technical support at 1-800-519-8794 when:
Multiple errors occur simultaneously
Error persists after following diagnostic steps
Control board or complex components need replacement
Refrigerant system work is required (certified technician only)
Safety concerns exist
See Also¶
Device Status Fields - Status field descriptions
MQTT Protocol - Error reporting via MQTT
Installation Manual - Complete technical specifications