Navien NPE-2 Code E517
DIP switch setting fault. The DIP switches inside the unit — the physical switches that tell the board what model it is and how it was installed — are in a combination the heater does not accept. Navien's instruction is to contact technical support.
Call a proThe verdict
Call a licensed plumber
This is a configuration fault, not a broken part, which usually makes it cheap — but the switches are inside the cabinet on a gas appliance, and setting them wrong has consequences the code will not catch. If the unit was recently installed or serviced, call that installer back rather than paying for a new diagnosis.
Typical cost: $0–$300
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
- If the unit was installed, serviced, or had a board replaced recently, contact whoever did that work — this code points at it.
- Do not open the unit to change switches yourself.
Frequently asked questions
What do the DIP switches control?
Model and capacity, gas type, and installation options. They are how the same board serves several models — which is also why a board swapped in without the switches being set correctly will not run.
Code E517 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:
Don't confuse this with
One other Navien NPE-2 code points at a switch too. They are different components in different places, and ordering a part against the wrong one is the most common way this fault gets expensive: