Navien NPE-2 Code E515
PCB fault. The control board has failed its own checks. Navien's owner-level instruction is worth noting: make sure the electrical cord is properly grounded. Board faults on this unit are often reported alongside grounding problems, so that is checked before the board is condemned.
Call a proThe verdict
Call a licensed plumber
Check the outlet and its ground first — Navien's own instruction, and far cheaper than the alternative. If the board really has failed, it is the most expensive electronic part in the heater and the replacement includes setting the unit's configuration again.
Typical cost: $150–$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-2 — not averaged across the brand.
Source: Navien NPE-2 User's Information Manual (p. 17), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Check the heater is plugged into a properly grounded outlet, on its own circuit, with nothing added recently — Navien's listed step.
- Check whether the unit is still within its parts warranty before booking.
- Contact your installer or Navien technical support.
Frequently asked questions
Why does grounding come up so often in Navien's codes?
Because several of the unit's sensing circuits reference ground, flame detection above all. A poor or reversed ground produces readings the board cannot make sense of, and those surface as faults in whatever circuit noticed first.
Code E515 on other Navien series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: