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Navien · Tankless water heater

E030 Exhaust overheating

High severity Navien NPE-2

What the control is telling you

Flue temperature went above 149 F (65 C) and the unit shut down.

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

  • Clogged cold water inlet filter
  • Scaled heat exchanger
  • High return water temperature in recirculation/combi systems

Test and repair steps

  1. Clean the cold water inlet filter.
  2. Flush the heat exchanger.
  3. When this system normally sees return water over 140 F (60 C), you may turn off the exhaust limit: open Installer Menu, then 2. Parameter Settings, then item 6. Exhaust Limit Control, and set Disable. Do this only with CPVC, PP or stainless steel venting, never PVC.
  4. Warning: with PVC exhaust, leave Exhaust Limit Control enabled (factory default).
  5. Check Status Information > 9. Exhaust Temp while firing.
  6. Reset once with the Back button on the front panel and note whether the code returns.
  7. Code back after a reset? Stay at the unit and 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.