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Navien · Tankless water heater

E445 Bypass mixing valve abnormal

Medium severity Navien NPE-2

What the control is telling you

The bypass mixing valve is not moving or reporting correctly.

Applies to: Navien NPE-A2 (built-in recirculation) and NPE-S2 condensing tankless water heaters: NPE-150S2, NPE-180A2/S2, NPE-210A2/S2, NPE-240A2/S2

Likely causes

  • Mixing valve motor or wiring fault
  • Valve stuck

Test and repair steps

  1. On S2 models run Service menu > 3. Test Mode > 5. Mixing Valve: valve drives fully open then closed over about 10 s and shows 0-56%; check the feedback.
  2. Check Status Information > 11. Mixing Valve.
  3. Check the valve connector and wiring.
  4. Reset once with the Back button on the front panel and note whether the code returns.
  5. Fix given phone Navien Technical Support, 1-800-519-8794.

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Source: Navien NPE-A2/S2 User's Information Manual (20049624A), 5.2 Understanding Error Codes, p.17. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.