Navien E438 Error Code: Circulation pump abnormal operation
Updated October 2026 · Sourced from Navien documentation
🧭 Check a few things first
The circulation pump (in a setup with an installed air handler unit) is not operating normally. The manual says to check that it is operating properly.
Is it safe to keep running? Check the steps below first. If the pump is running and the code stays, call a licensed technician.
E438 at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| E438 Error code shown on the front panel display | Circulation pump abnormal operation | NPE-180A2, NPE-210A2, NPE-240A2, NPE-180S2, NPE-210S2, NPE-240S2 condensing tankless water heaters |
Check this first
Only steps a homeowner can do safely. Do not open electrical panels or the burner area.
- Check that the circulation pump has power and is running.
- Turn the unit off with the Power button, wait a minute, then turn it back on to see if the code clears.
🛑 Stop and call a licensed pro if
- If the pump is running and the code stays, call a licensed technician.
- You smell gas. Leave the house, do not touch switches, and call your gas utility from outside.
- Codes for flame failure, overheating, venting or the control board that return after one reset.
- Water leaking from the heater, the relief valve discharging, or scorching around the burner area.
- A carbon monoxide alarm sounds. Get everyone outside and call 911 or the fire department.
Safe first steps for any Navien code
- Write down the exact code shown on the controller or the number of status light flashes.
- Turn the water heater power off and back on (or press the reset button the manual describes) once. If the code comes back, stop resetting.
- Make sure the gas supply valve to the heater is open and other gas appliances in the home are working.
- Make sure the cold water supply valve is fully open and hot water taps are not partly closed.
- Look at the outside vent terminal for snow, ice, leaves or anything blocking it (look only).
Source: Navien NPE Condensing Water Heaters User's Information Manual (NPE-2, rev 201202), 5.2 Understanding Error Codes, p.17. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
Ryan Giles · Red Seal Certified Plumber · Ask a plumber · Ask an HVAC technician
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