A bypass valve is activated as Thermostatic Radiator Valves (TRVs) close, sensing that selected room temperatures have been reached.
Here's a more detailed explanation:
When a central heating system is running, the boiler pumps hot water through the radiators. Each radiator often has a TRV, which allows the user to set a desired temperature for that room.
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Normal Operation: When the room temperature is below the TRV setting, the valve is open, allowing hot water to flow through the radiator and heat the room.
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Reaching Temperature: As the room reaches the set temperature, the TRV gradually closes, restricting the flow of hot water into the radiator.
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Bypass Valve Activation: If many or all of the TRVs in the system close, the boiler pump would be pushing water against a closed system, which could damage the pump or the boiler. This is where the bypass valve comes in. As the TRVs close, the pressure in the system increases. This pressure increase is what causes the bypass valve to open. The bypass valve provides an alternative path for the water to flow, diverting it back to the boiler's return line. This maintains a minimum flow rate through the boiler, preventing damage and ensuring efficient operation.
In essence, the bypass valve is activated by the back pressure created when TRVs close, ensuring a continuous flow of water through the boiler and pump circuit.
