Navien NPE-2 Code E615
Input and memory fault. The board is reporting a fault between what it is being told and what it has stored. Navien groups it with the other board-level faults and gives no owner-level step: contact technical support.
Call a proThe verdict
Call a licensed plumber
Board-level, with no owner action listed. It is worth checking the warranty position before booking, because the likely outcome is a control board.
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-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
- Note any recent service or power event.
- Check whether the unit is still within its parts warranty.
- Contact your installer or Navien technical support.
Frequently asked questions
Is E615 the same as E594?
They are neighbours, not twins. E594 is the stored memory itself failing to read back; E615 is a mismatch between inputs and memory. Both are board-level and both are diagnosed the same way.
Code E615 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: