Navien · Tankless Water Heater Serious

E515 — PCB / Control Board Abnormal

Self-diagnostic detected an internal PCB malfunction — corrupted memory, watchdog reset, or relay feedback error.

Keep using it?
Limited use only
DIY difficulty
Hard
Verified against
navieninc.com ↗

How to fix it

  1. Power off at the breaker for 5 minutes, then restore — confirm code returns.
  2. Inspect the control compartment for moisture or burn marks; address any leak first.
  3. If code persists with no obvious external cause, replace the PCB.
  4. Install a whole-house or point-of-use surge protector after replacement.

Why it happens

Typical signs: E515 on display · Unit unresponsive · Random shutdowns · Display glitches

  • PCB failure Internal control board fault.
  • Power surge Lightning or surge damaged board components.
  • Moisture intrusion Condensate or leak reached the control compartment.

Parts you may need

If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.

  • Navien PCB / control board Common replacement
    Amazon →

More Navien tankless water heater codes

E003 E003 — Ignition Failure E012 E012 — Flame Loss E016 E016 — Overheat / High-Limit Trip E027 Tankless E027 — Sensor Abnormality E030 E030 — Abnormal Exhaust Temperature (Flue Overheat) E046 E046 — Abnormality in Limit Control (Heat-Exchanger High-Limit)

All Navien codes → All tankless water heater codes →

Frequently asked questions

What does the E515 code mean on a Navien tankless water heater?

Self-diagnostic detected an internal PCB malfunction — corrupted memory, watchdog reset, or relay feedback error.

What causes the E515 code on a Navien tankless water heater?

PCB failure: Internal control board fault. Power surge: Lightning or surge damaged board components. Moisture intrusion: Condensate or leak reached the control compartment.

Is it safe to keep using a Navien tankless water heater with a E515 error?

Limited use only. This is rated a serious-severity fault.

How do I fix E515 on a Navien tankless water heater?

Power off at the breaker for 5 minutes, then restore — confirm code returns. Inspect the control compartment for moisture or burn marks; address any leak first. If code persists with no obvious external cause, replace the PCB.

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: navieninc.com.