E027 Moderate Easy DIY

Navien Tankless Water Heater E027 — Gas Type Setting Error

Navien Tankless Water Heater · Error code E027

What E027 Means

The dip-switch gas-type setting does not match the connected fuel, or the unit detects combustion characteristics inconsistent with the configured fuel.

Symptoms

  • E027 on display
  • Unit will not fire
  • Yellow flame or sooting if it does fire briefly

Common Causes

1
NG/LP dip switch set incorrectly

Common after a PCB swap or fuel conversion.

2
Conversion kit not installed correctly

Wrong orifice or regulator for the fuel in use.

How to Fix It

  1. Confirm what fuel is actually supplied to the unit (NG or LP).
  2. Power off and check the gas-type dip switch on the PCB against the manual.
  3. If converting fuels, install the correct Navien conversion kit per the conversion instructions.
  4. Restore power; verify firing and combustion are normal.

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 E030 E030 — Fan / Combustion Blower Fault E046 E046 — Mixing Valve Error

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.