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Navien · Combi boiler

E030 Exhaust overheat (abnormal exhaust temperature)

High severity Navien NCB-HNavien NFC-H

What the control is telling you

Flue gas temperature went above the control limit (the boiler limits exhaust to about 149°F (65°C) when PVC venting is selected). NFC-H manual lists the reset type as: Manual reset / Alarm.

Applies to: Navien fire-tube combi boilers, NFC-H series (NFC-250/200H, NFC-250/175H) and NCB-H combi boilers (NCB-250/150H, NCB-240/130H, NCB-240/110H, NCB-190/080H, NCB-190/060H)

Likely causes

  • High return water temperature with exhaust temperature control enabled
  • Scaled heat exchanger / poor heat transfer
  • Faulty exhaust temperature sensor

Test and repair steps

  1. Check Status Information > 24. Exhaust Temp and return temperature.
  2. If the system needs return water hotter than 140°F (60°C), DIP SW2 #8 must be set ON - and then the exhaust must be CPVC, polypropylene or stainless steel, not PVC.
  3. Warning: never set DIP SW2 #8 ON with PVC exhaust venting.
  4. Check the heat exchanger for scale and flush if needed.
  5. Code keeps returning? Phone Navien Technical Support, 1-800-519-8794.

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Source: Navien NCB-H Installation & Operation Manual, 11.7 Understanding Error Codes, p.129-130; Navien NFC-H Installation Manual, 11.7 Understanding Error Codes, p.127-128. 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.