Illustration of a small water flow sensor with a visible paddle wheel, disconnected on a workbench.

Navien Error Code E515 (PCB Error)

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Navien error code E515 points to a fault on the unit’s control board (PCB), and is frequently tied to grounding problems or a power surge. One source’s entire fix for this code is simply “confirm proper grounding” — which is a real starting point, but not the whole story if the board itself has failed.

Illustration of a small water flow sensor with a visible paddle wheel, disconnected on a workbench.
Illustration of a small water flow sensor with a visible paddle wheel, disconnected on a workbench.

Likely Causes, Ranked

  1. Poor or missing equipment grounding
    The single most commonly cited cause for this code.
  2. Power surge or voltage spike
    Can damage sensitive board components even without a visible fault elsewhere.
  3. Failed control board
    If grounding checks out and the code persists, the board itself may need replacing.

Step-by-Step Diagnosis

  1. DIY WITH CAUTION
    Verify the unit’s electrical ground

    Check the ground wire connection at the unit and at the panel — this alone resolves E515 for some owners.
  2. DIY SAFE
    Check for recent power events

    A storm, outage, or nearby electrical work around the time the code first appeared is a useful clue.
  3. PRO ONLY
    If grounding is confirmed solid and the code persists

    The control board itself needs professional diagnosis and likely replacement.

FAQ

Is E515 dangerous?

Not in the sense of a gas or fire hazard — it’s an electronics fault. But don’t keep resetting it repeatedly without checking the ground; that’s the documented fix most often cited.

Written by HotWater Decoded — water heater repair specialists. Technically reviewed by a licensed technician on our team.

Sources

  • waterheaterhub.com troubleshooting entry

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