Grant Short Cycling

Boiler frequently cycles on and off, providing inconsistent heating and hot water temperatures.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Oversized boiler for system, Incorrect control settings, Faulty room thermostat or cylinder stat, Blocked or undersized bypass

Safety: No immediate hazard, but short cycling reduces efficiency and lifespan.

User checks:

Ensure room thermostat is located away from direct heat sources and set to a stable temperature.
Check that TRVs are not all closed, leaving no open circuit.

Engineer actions:

Review boiler output settings and reduce if the Grant model allows modulation.
Check operation and location of room and cylinder thermostats.
Verify presence and correct setting of an automatic bypass valve to maintain minimum flow.

Medium 3/5

Automatic bypass valve

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