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Glow Brand · Boiler troubleshooting

No DHW - no storage tank

Glow Combi C95 & C140

What is going on

Boiler runs but hot tap water is not produced, direct-fired DHW with no tank.

Likely causes

  • DHW mode not set correctly
  • Insufficient DHW flow
  • Blocked cold water inlet filter screen
  • Faulty or miswired flow sensor
  • DHW setpoint too low

Check in this order

  1. Confirm DHW Mode is set to 5 (Installer Menu 2.035).
  2. Check DHW flow rate (User Menu 1.062). The boiler goes into DHW mode when flow exceeds 0.5 gpm (1.9 l/m).
  3. If flow is low, check the water supply and DHW piping, and clean the filter screen on the domestic cold water inlet.
  4. Check the wiring to the flow sensor and replace the sensor if needed.
  5. Compare DHW setpoint (User Menu 0.048) with DHW temperature (Information Menu 1.002). The burner fires when DHW temperature falls below setpoint and flow exceeds 0.5 gpm.
  6. If needed, raise the DHW setpoint (Installer Menu 2.048). A setpoint of 125°F (52°C) is recommended.
  7. If the radiator symbol flashes and DHW priority time is enabled, the priority time may have expired. Cycle power and consider raising the DHW priority time (Installer Menu 2.043).

Applies to: C95 & C140 Glow Combi boilers without storage tank

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Source: C-300 C95-C140 Installation & Operation Manual, p. 73. 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.