Plumbing diagram for wood burning boiler and a thermal relief valve.
The purpose of the thermal relief is to, in the event of boiler overheating, release hot water from within the boiler and replace same volume with cold water coming from the mains therefore drastically reducing boiler temperature. This stops the water from changing physical state and causing a possible boiler failure. This is not a device to be used as regular solution but one for emergency.
In conjunction with a TRV, diagram is also showing a leak off radiator.
If no buffer tank is fitted, leak off radiator is first line of defence against temperature build up in a solid fuel boiler central heating system.
The leak off heat sink or a radiator is allows hot water through an actuating valve which is linked and controlled by a temperature sensor, so that once the water inside the boiler reaches pre-set value of say 80 or 85 degree Celsius, valve opens allowing hot water to lose temperature through convection.
This is a basic diagram with some parts of central heating system being omitted for simplification purposes.
