Product troubleshooting

Navien NWP500 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 NWP500 Series

Search error codes

Code	Meaning	System area	Safe first step	Action
E096	Abnormal upper electric heater operation	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
E097	Abnormal lower electric heater operation	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
E326	Dry fire condition	Water flow / hydronics	Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service.	View details
E407	Hot water outlet temperature sensor issue	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
E445	Abnormal mixing valve operation	Water flow / hydronics	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
E480	Tank temperature sensor issue	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
E481	Lower tank temperature sensor issue	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
E515	Abnormal operation: PCB	Controls / communication	Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service.	View details
E517	Abnormal operation: DIP switch setting	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
E593	Abnormal operation: front panel key	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
E594	Abnormal operation: EEPROM	Controls / communication	Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service.	View details
E595	Abnormal operation: communication or memory	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
E596	Abnormal operation: communication or memory	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
E598	Abnormal operation: communication or memory	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
E615	Abnormal operation: input and memory	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
E743	Abnormal temperature sensor or system control operation	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
E766	Abnormal safety device or water heater control operation	Water flow / hydronics	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
E781	Abnormal communication or control operation	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
E798	Abnormal appliance control operation	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
E799	Abnormal appliance control operation	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
E901	Abnormal sensor or control operation	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
E907	Abnormal sensor or control operation	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
E908	Abnormal sensor or control operation	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
E909	Abnormal sensor or control operation	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
E910	Abnormal sensor or control operation	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
E911	Abnormal sensor or control operation	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
E912	Abnormal sensor or control operation	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
E913	Abnormal sensor or control operation	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
E914	Abnormal sensor or control operation	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
E915	Abnormal sensor or control operation	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
E916	Abnormal sensor or control operation	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
E920	Abnormal sensor or control operation	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
E940	Abnormal sensor or control operation	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
E990	Abnormal safety or control operation	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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Michele Z.

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

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always available, easy to get a hold of, as a property manager I get lots no heat emergency, usually get to it same day or next day

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Anna F.

They showed up within an hour of me making the call on a Sunday. They fixed our system and taught us how to replace the fuse in the future. We would definitely call again.

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