Navien E773
Navien E773: wrong gas type detected
Short answer
Navien E773 means the water heater is using the wrong gas: the gas supplied does not match the gas type the unit is set up for, such as propane supplied to a natural gas setting. It is listed for NPE-2 models. Wrong gas causes abnormal combustion, so Navien's manual says to contact technical support.
In this guide
Natural gas and propane burn differently, and a heater must be configured for the one it receives. E773 means the heater has detected a mismatch.
The meaning and recommended action below come from Navien's User's Information Manual for NPE-2 condensing water heaters (NPE-180A2, NPE-210A2, NPE-240A2 and the S2 models). Navien technical support: 1-800-519-8794.
This code is listed for the current NPE-2 generation. The original NPE-A and NPE-S models do not have it.
If you smell gas, do not reset the unit or touch switches. Leave the building and call your gas utility from outside.
When it happens
- A new installation connected to the wrong gas supply
- A gas conversion that was not completed correctly
- A settings error after service
What to do
Turn the heater off and call your installer or Navien technical support. Conversions must use Navien's official conversion parts and procedure. Navien's warranty excludes improper conversions and operation on a gas type not specified for the heater.
For related setup problems, see Navien E788, a mismatch between gas settings on the control board and the front panel.
Before you call
Have the model number and serial number from the rating plate on the side of the unit ready, along with the date it was installed and the exact code. Navien asks for this information when you contact technical support, and your installer should be your first call for warranty service.
See every code on our Navien error codes page.
Common questions
What is the difference between Navien E773 and E788?
E773 means the gas supplied does not match the heater's setting. E788 means the gas settings on the board and the front panel do not match each other.
Was this article helpful?
Sorry about that. What was missing?
Please do not include personal information. Links are not accepted.
Thanks for your feedback. It helps us improve our guides.
Other Navien codes
| Code | Meaning |
|---|---|
| E003 | Ignition failure |
| E004 | False flame detection |
| E012 | Flame loss |
| E016 | Heat exchanger overheat |
| E030 | Abnormal exhaust temperature |
| E031 | Burner overheating |
| E046 | Limit control (high limit switch) abnormal |
| E047 | Exhaust temperature sensor (thermistor) open or short |
| E060 | Dual venturi abnormal operation |
| E109 | Fan motor abnormal operation |
| E110 | Exhaust blockage (condensate blockage) |
| E407 | Hot water outlet temperature sensor open or short |
| E421 | Cold water inlet temperature sensor open or short |
| E432 | Cold water inlet 2 sensor open or short |
| E434 | Water adjustment valve fault |
| E438 | Circulation pump fault |
| E439 | Flow sensor fault |
| E441 | Second hot water temperature sensor open or short |
| E445 | Bypass mixing valve fault |
| E515 | Control board (PCB) abnormal operation |
| E517 | DIP switch setting fault |
| E593 | Front panel key fault |
| E594 | EEPROM (memory) fault |
| E615 | Input and memory fault |
| E736 | Cascade communication fault |
| E740 | Outdoor temperature sensor fault |
| E760 | Flushing or service alarm |
| E762 | Vent pipe not properly inserted |
| E773 | Using the wrong gas |
| E782 | Main panel communication fault |
| E785 | Flow switch or flow sensor fault (with AHU) |
| E788 | Gas type mismatch between board DIP switch and front panel |