Navien tankless water heater code E782
Main panel communication fault. Code E782 means the same thing on all 2 Navien series documented here — but the fix, and what it costs, is still worth reading for your exact unit.
What code E782 means on each Navien series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| NPE-2 | Main panel communication fault | Call a pro | $150–$900 |
| NPE-A / NPE-S | Main panel communication fault | Call a pro | $150–$900 |
Each row opens the full page for that generation. We hold manuals for NPE-2 and NPE-A / NPE-S, and each one gets its own reading of code E782 — what Navien documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 2 series in four columns, which is enough to route you and not enough to explain anything. This is the Navien wording behind each row, one entry per manual, so you can see where the 2 readings of code E782 agree and where they part company.
NPE-2 — Main panel communication fault
The front panel and the control board have lost reliable communication. Navien's instruction is to contact technical support.
NPE-A / NPE-S — Main panel communication fault
The unit has lost communication with its main panel. Navien's instruction is to contact technical support.
Does it matter which Navien you have?
NPE-2 and NPE-A / NPE-S all route code E782 the same way: a professional, at $150–$900. That makes it one of the Navien numbers you can act on before working out which unit you own.
Which Navien do you have?
On the 2 series that report code E782, the model number on the rating label starts NPE — match yours against the 13 listed below. You can also use the full model-number decoder.
Where this comes from
Source: Navien NPE-2 User's Information Manual (p. 18), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Source: Navien NPE Operation Manual (NPE-A / NPE-S) (p. 16), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Parts, guides and symptoms behind code E782
Code E782 on these 2 Navien series points at 2 parts and 1 symptom, each named by the manufacturer's own procedure for this code.