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Navien · Tankless water heater

E046 Limit control abnormal

High severity Navien NPE-2

What the control is telling you

The water temperature high-limit control reported a fault.

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

  • Water overheated
  • High limit switch or wiring fault

Test and repair steps

  1. Check for low water flow or scale (clean inlet filter, flush heat exchanger if needed).
  2. Check the high limit switch connector and wiring.
  3. Reset once with the Back button on the front panel and note whether the code returns.
  4. 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.