Grant overheat thermostat trip Fault Code (Vortex Pro External)

Safety disclaimer

Fault code summary

Manufacturer

Grant

Fault code

overheat thermostat trip

Fault type

Overheating, Safety lockout

Severity

high

Reset

The manual identifies a manual overheat-thermostat reset; a recurring trip requires a qualified engineer and should not be repeatedly reset.

Applicable models

Vortex Pro External 15-26, Vortex Pro External 26-46, Vortex Pro External 46-70

Quick answer

The safety overheat thermostat automatically switches the boiler off if the heat exchanger exceeds 110°C ± 3°C.

What does this fault code mean?

The safety overheat thermostat automatically switches the boiler off if the heat exchanger exceeds 110°C ± 3°C.

Common causes

• Control malfunction causing overheating

Symptoms

• Boiler automatically switches off

What can the homeowner safely check?

• Allow the appliance to cool and do not remove the casing or reset internal safety devices.

Boiler reset information

The manual identifies a manual overheat-thermostat reset; a recurring trip requires a qualified engineer and should not be repeatedly reset.

When should I call an engineer?

Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.

Engineer diagnosis

• A qualified engineer should investigate overheating, circulation, thermostat operation and the oil burner.

Applicable boiler models

• Vortex Pro External 15-26
• Vortex Pro External 26-46
• Vortex Pro External 46-70

Related fault codes

• burner lock-out — Vortex Pro External

  The Grant Vortex Pro External control panel provides a burner lock-out reset button; this is an oil-burner indication rather than a numeric boiler code.

  Read fault code
• pump Run/Fault LED: red — Vortex Pro External

  The Wilo-PARA circulating-pump table identifies a constant red Run/Fault LED as the pump being stopped.

  Read fault code

Manufacturer documentation

The boiler is fitted with an overheat thermostat which will automatically switch off the boiler if the heat exchanger exceeds a pre-set temperature of 110°C ± 3°C; the control panel includes the manual reset button for the overheat thermostat.

Last verified

2026-09-12

Frequently asked questions