Navien NPE-A / NPE-S Code E615
Input and memory fault. The board's stored configuration or its inputs are not reading back correctly. Navien's instruction is to contact technical support; there is no owner-side remedy.
Call a proThe verdict
Call a licensed plumber
A board-level fault. Ask what is actually being replaced before agreeing — this can end at reprogramming or at a new board, and the difference is most of the bill.
Typical cost: $200–$1,100
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 the unit's age. On a first-generation NPE a board replacement is a large fraction of a new heater, and that comparison is worth making.
- Book a licensed professional.
Code E615 on other Navien series
Other Navien series report code E615 under the same fault name, but each manual is transcribed separately and they do not read alike: