Navien NPE-A / NPE-S Code E782
Main panel communication fault. The unit has lost communication with its main panel. Navien's instruction is to contact technical support.
Call a proThe verdict
Call a licensed plumber
A communication fault between the control board and the panel — cabling, connector, or one of the two boards. Diagnosis is inside the cabinet.
Typical cost: $150–$900
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the NPE-A / NPE-S — not averaged across the brand.
Source: Navien NPE Operation Manual (NPE-A / NPE-S) (p. 16), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Note whether the display is blank, frozen, or showing the code — that distinction narrows it before anyone arrives.
- Book a licensed professional.
Code E782 on other Navien series
Other Navien series report code E782 under the same fault name, but each manual is transcribed separately and they do not read alike:
Don't confuse this with
One other Navien NPE-A / NPE-S code points at a link between two boards too. They are the same symptom reported from a different place in the unit, so which one the display shows is what tells you where to look: