Navien tankless descaling kit
Useful for E006 and E016 overheating faults caused by scale and restricted flow.
$60-$180
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Navien Error Codes — Quick Reference
Navien tankless water heaters (NPE-A, NPE-S, NPE-2, NHB, NCB series) display fault codes on the front panel LED display. Codes appear as “E” followed by three numbers. Navien also uses a NaviLink or Navien Connect app on WiFi-enabled models for remote diagnostics.
| Code | Meaning | Quick Fix |
|---|---|---|
| E001 | Abnormal ignition | Check gas supply and igniter |
| E002 | Flame failure after ignition | Gas pressure or flame sensor |
| E003 | Ignition failure (all retries) | Gas valve, igniter, or gas supply |
| E004 | False flame detection | Flame sensor or gas valve |
| E006 | Over-temperature at heat exchanger | Flush scale; check flow |
| E007 | Flow sensor fault | Check flow sensor or filter |
| E009 | Fan motor fault | Check fan motor and wiring |
| E010 | Gas pressure sensor fault | Check gas pressure sensor |
| E012 | Flame rod circuit fault | Check flame sensor wiring |
| E013 | Rollout switch | Inspect venting; check switch |
| E016 | Overheating | Water scale; check flow rate |
| E030 | Exhaust thermistor fault | Check exhaust thermistor |
| E302 | Abnormal water temperature | Flow issue or thermistor fault |
Need Replacement Parts?
Before ordering, match the water-heating part to the model number, electrical rating, and confirmed E-code. Check Navien descaling kits, flow sensors, flame rods, fan motors, thermistors, and service-valve parts on Amazon - prices and availability change frequently.
Most Common Codes
E001 / E003: Ignition Failure
The unit attempted to ignite and failed. Start by verifying the gas supply valve is fully open and that there’s no outage on your gas meter. Check gas pressure — Navien requires a minimum of 4” WC for natural gas at the unit inlet under fire conditions. If pressure is adequate, the igniter or gas valve may be failing.
Also verify the condensate drain is clear — a blocked condensate drain on an NPE model can prevent the inducer from starting and cause E001.
E002: Flame Loss After Ignition
The unit lit but the flame went out during operation. Common causes: fluctuating gas pressure, a partially clogged gas valve strainer, or a dirty or faulty flame sensor rod. Navien flame sensors are accessible by removing the burner access cover on the front of the unit.
E006 / E016: Overheating / Heat Exchanger Scale
On Navien NPE units installed in hard water areas, scale builds up inside the stainless steel heat exchanger and restricts flow, causing overheating faults. Navien recommends annual descaling flush with white vinegar (or commercial descaler) using hose bib connections on the cold inlet and hot outlet.
Descaling procedure:
- Connect a submersible pump to the cold inlet hose bib.
- Connect the hot outlet hose bib to a bucket of white vinegar.
- Circulate vinegar through the heat exchanger for 45–60 minutes.
- Flush with clean water for 5 minutes.
E007: Flow Sensor Fault
The cold water inlet flow sensor is not registering flow correctly. Remove and clean the flow sensor (unscrew the cold inlet fitting cap) — the turbine sensor inside collects debris from the water supply. Clean the plastic turbine paddle with water and reinstall.
E009: Fan Motor Fault
The combustion air fan has failed or is not reaching speed. Check that nothing is blocking the air intake or exhaust vents. If the fan runs but is noisy (bearing noise), it should be replaced. If the fan doesn’t run at all, check the fan motor harness connection on the control board.
E013: Rollout Switch
Hot gases rolled back into the combustion chamber and tripped the manual-reset rollout switch. This is a venting problem — check for: blocked vent pipe, disconnected vent joint, recirculating combustion air (intake too close to exhaust), or downdraft conditions. Fix the venting root cause before resetting the switch.
When to Call a Pro
E013 (rollout) and E004 (false flame detection) require investigation of the gas valve and combustion circuit that goes beyond homeowner scope. Navien NPE units use a complex gas/air proportional valve — adjustment and replacement require factory training.