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Back to Navien NAZ Series

Navien NAZ Series troubleshooting and error codes

Use this table to identify what the visible code may mean and what information to share when scheduling service. Keep checks simple and visible; do not open electrical, refrigerant, gas, or sealed equipment compartments.

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Error-code table

Search codes for NAZ Series

Code Meaning System area Safe first step Action
F0 Indoor ambient temperature sensor error Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
F4 Outdoor ambient temperature sensor error Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
F5 Outdoor heat exchanger temperature sensor error Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
F6 Outdoor heat exchanger outlet temperature sensor error Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
F7 Compressor discharge temperature sensor error Temperature / sensor Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
F8 Outdoor pressure sensor error Temperature / sensor Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
F9 Inverter module heat sink temperature sensor error Temperature / sensor Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
FA Suction temperature sensor error Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
FB DC fan motor temperature sensor error Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
FC Economizer inlet temperature sensor error Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
FD Economizer outlet temperature sensor error Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
FE Module temperature sensor error Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
FF Indoor/outdoor communication or sensor error Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
P1 High pressure protection Water flow / hydronics Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
P2 Low pressure protection Water flow / hydronics Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
P3 Compressor current protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
P4 Compressor discharge temperature protection Temperature / sensor Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
P5 Compressor drive protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
P6 Communication protection Controls / communication Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
P8 Module high temperature protection Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
P9 DC fan motor protection Airflow / fan Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
PC Outdoor compressor drive current protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
PD Outdoor compressor drive or refrigerant-system protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
H0 Indoor fan motor malfunction Airflow / fan Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
H1 Outdoor fan motor malfunction Airflow / fan Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
H2 Compressor desynchronization protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
H3 Compressor overload protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
H4 System abnormal protection Equipment control Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
H5 IPM module protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
H6 DC fan motor error Airflow / fan Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
H7 Compressor drive error Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
H8 PFC protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
HC PFC module protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
HE Compressor demagnetization protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
L0 Indoor control board EEPROM error Controls / communication Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
L1 Outdoor control board EEPROM error Controls / communication Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
LA Indoor/outdoor model or communication mismatch Controls / communication Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
LB Model matching or setup error Equipment control Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
LC Compressor startup failure Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
LD Compressor phase or drive protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
LE Compressor stalling protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
LF Compressor speed or drive protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
d0 System control status code Equipment control Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
df Defrost operation status Equipment control Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
dC System control status code Equipment control Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
ATL Low ambient temperature protection/status Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
PRH Preheating status Equipment control Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details

Safety note

What is safe to check before service

These pages are meant to help document the issue, not replace diagnosis. GreenFlow should handle pressure-switch, electrical, refrigerant, lockout, recurring, and warranty-related conditions.

Safe visible checks

  • Thermostat display and settings
  • Filter condition and return-air path
  • Visible outdoor-unit obstruction
  • Photos of the code, unit, and nameplate

Stop and call

  • Repeated lockouts or recurring faults
  • Pressure-switch or sensor faults
  • Electrical odor, unusual noise, or ice buildup
  • Any sealed cabinet, refrigerant, gas, or warranty issue

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Jahangir R.

They were very organized to communicate and be on time to come to look at my air condition to fix it.

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Just had a service call because my tankless water heater stopped working with E110 code. Andrey located the root cause real quick and fixed the issue within half an hour, also gave reasonable recommendations for further maintenance.

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Andrey was professional, prompt, smart, thorough and exceedingly pleasant. We are likely switching our current HVAC company to Green Flow.

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I had a breakdown of my cooling system and Hanna at Green Flow responded to my request right away. They scheduled me same day. The team at Green Flow was easy to communicate with over phone and text. They kept me updated on delays on arrival of the...

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