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Glow Brand · Boiler troubleshooting

No DHW - with storage tank (sensor or aquastat)

Glow Combi C95 & C140

What is going on

Boiler does not heat the storage tank. Checks differ for sensor and aquastat setups.

Likely causes

  • Tank sensor or aquastat miswired
  • DHW mode set for the wrong tank type
  • DHW priority time expired
  • DHW circulator not running
  • Plumbing not per the piping figures

Check in this order

  1. Storage tank with sensor set DHW Mode to 1 (Installer Menu 2.035) and confirm the tank sensor is wired per Figure 11.12.
  2. Storage tank with sensor read tank temperature in Information Menu 1.002. Compare DHW temperature (User Menu 0.048) with the tank setpoint (Installer Menu 2.115). Demand starts when the tank falls 9°F below setpoint. The default tank setpoint is 140°F.
  3. Storage tank with aquastat set DHW Mode to 2 (Installer Menu 2.035), unless the alternate connection method is used. Confirm the dry-contact aquastat is wired per Figure 11.12.
  4. Storage tank with aquastat confirm the aquastat is calling. The faucet symbol flashes on demand. The maximum tank setpoint with an aquastat is 135°F.
  5. If the radiator symbol flashes, the DHW priority time may have expired. Cycle power and consider raising the DHW priority time (Installer Menu 2.043) and/or the tank setpoint (Installer Menu 2.115).
  6. If the faucet symbol flashes, confirm the DHW circulator runs. It should be wired to terminals 9 and 10 (Figure 9.1).
  7. Confirm plumbing matches Figure 6.3 or Figure 6.5.

Applies to: C95 & C140 Glow Combi boilers with DHW 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.