Can I fix Navien code E773 myself?

Start with these safe checks: Turn the heater off. Gas type settings must be checked by a qualified gas technician.

When should I call a technician for code E773?

Gas type settings must be checked by a qualified gas technician. Smell gas? Leave right away, don't touch light switches or phones inside, and call your gas utility or 911 from outside. Never open a gas valve, burner, gas line, vent or flue connection, or bypass a safety switch. Repeated lockouts, scorching, soot, or a CO alarm mean shut it off and call a licensed gas technician.

Navien Tankless Water Heater Error Code E773 / E788: Wrong gas /…

What E773 means

The heater is using the wrong gas (E773), or the gas type set on the panel and DIP switch don't match (E788).

Also shown as: E788, depending on the model.

Likely causes

Gas type set wrong
Wrong gas supplied

Safe first checks

Turn the heater off.

When to stop

Gas type settings must be checked by a qualified gas technician.

Checked against: Navien NPE-2 user's information manual: understanding error codes. Codes can differ by model and year, so confirm with your owner's manual.