Navien Error Code E777: System Error Code

Severity
Warning
Type
digital display
Where to look
front panel
Estimated repair cost: $100 — $350 (parts + labor)
Warning: Your Navien boiler has encountered a system error. It's safe to operate, but needs professional attention.

How to Fix Navien Code E777

  1. Check if the remote control is properly paired with the boiler. Try removing and re-adding it.
  2. Ensure there are no other electronic devices nearby that could be causing interference.
  3. If the issue persists, contact a professional HVAC technician for repair.

How to Reset Navien Code E777

  1. Turn off the unit using the power button on the front panel.
  2. Turn off the gas supply valve.
  3. Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
  4. Restore power at the breaker, then open the gas valve.
  5. Turn the unit back on. If the error returns, the underlying issue needs repair.

What does E777 mean?

The Navien E777 error code indicates a communication issue between your boiler's main board and the remote control. This isn't an immediate safety concern, but it will prevent you from using the remote to control your boiler. The boiler will continue to function normally using the local controls.

Affected Models

Source Documentation

ManualPageReasonAction
NFB-H Installation & Operation Manual 116 Low Water Cutoff Activated Check supply water.
Navien NCB-H Installation & Operation Manual 130 Low Water Cutoff Activated ● Check the LWCO wiring connection. ● Ensure that the system water level is appropriate. ● Add make-up water to the system if necessary.
Navien NFB-H Installation & Operation Manual 116 Low Water Cutoff Activated Check supply water.
Navien NFC-H Installation & Operation Manual 128 Abnormal operation: LWCO limit (external device) Auto RESET
Navien NHB-H Installation & Operation Manual 119 Low Water Cutoff Activated Check supply water.

Replacement Parts

PartOEM NumberEst. Cost
Main Board
Remote Control

Related Codes on Same Models

CodeDescriptionSeverity
E001 Ignition Failure Warning
E003 Abnormal Ignition Warning
E004 False Flame Detection Warning
E012 Flame Loss Warning
E016 Overheating Warning
E030 Exhaust Overheat Sensor Warning
E031 Inlet Thermistor Open/Short Warning
E046 Outlet Thermistor Open/Short Warning
E047 DHW Thermistor Open/Short Warning
E060 Fan Motor Abnormality Warning