E515 Serious Hard — consider a tech

Navien Tankless Water Heater E515 — PCB / Control Board Abnormal

Navien Tankless Water Heater · Error code E515

What E515 Means

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

Symptoms

  • E515 on display
  • Unit unresponsive
  • Random shutdowns
  • Display glitches

Common Causes

1
PCB failure

Internal control board fault.

2
Power surge

Lightning or surge damaged board components.

3
Moisture intrusion

Condensate or leak reached the control compartment.

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.

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.

Common replacement Navien PCB / control board View on Amazon→

More Navien Tankless Water Heater Codes

E003 E003 — Ignition Failure E003C E003C — Cascade Ignition Failure E012 E012 — False Flame / Flame Loss E016 E016 — Overheat / High-Limit Trip E027 E027 — Gas Type Setting Error E030 E030 — Fan / Combustion Blower Fault

All Navien codes → All tankless water heater codes →

Verified against manufacturer documentation: navieninc.com

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.