Navien E788
Navien E788: gas type setting mismatch
Short answer
Navien E788 means the gas type set with the DIP switches on the control board does not match the gas type set on the front panel. Navien's manual says to check the supplied gas type and make the setting on the panel DIP switch and the panel match. It usually appears after installation, a board replacement or a conversion.
Navien NPE-2 heaters store the gas type in two places: DIP switches on the control board and a setting in the front panel. E788 means they disagree.
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.
What Navien recommends
- Confirm which gas the heater is actually connected to: natural gas or propane. The front panel shows a gas indicator when the unit is configured for propane.
- Match the gas type setting on the control board DIP switches and on the front panel to that gas.
Changing DIP switches means opening the unit, so this is a job for the installer or a qualified technician, with the power off.
If you smell gas, do not reset the unit or touch switches. Leave the building and call your gas utility from outside.
Related codes
If the heater detects that the gas supplied does not match its settings, it shows E773 instead. For settings errors in general, see E517.
How to reset it
Navien says you can try resetting the water heater by pressing the Back button on the front panel. If the code returns, the cause is still there and the unit needs service.
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
Can I fix Navien E788 from the front panel?
The board DIP switches must match too, and those are inside the unit. Have a qualified technician make both settings agree.
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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 |