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Glow Brand · Boiler troubleshooting

Boiler shows FILL and will not fire

Glow Combi

What is going on

Display shows FILL, burner will not fire. Low water pressure is the lock.

Likely causes

  • Water pressure below 4 PSI at the boiler inlet
  • Water pressure below 10 PSI, which the pressure sensor uses to inhibit firing
  • Slow leak, failed expansion tank or fill valve that is not holding pressure

Check in this order

  1. Read the pressure on the boiler gauge or display, with the system cold.
  2. Refill the system to at least 10 PSI.
  3. Find and repair leaks, because pressure that keeps dropping means water is going somewhere.
  4. Check the expansion tank charge and the fill valve.
  5. Confirm the burner fires after pressure is restored.

Applies to: C95 & C140

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Source: Glow Brand C95 & C140 installation & operation manual, pp. 33-34. Written in our own words; check the manual for your exact model.

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.