Boiler Fault Finder

Diverter valves

Diverter valves Reasons a diverter valve will fail to move: Wax capsule faulty Bobbin assembly faulty Faulty motorised valve head Seized push rod Contaminated system water / blockages (magnetite) Faulty pump Faulty primary flow switch and / or microswitch Faulty printed circuit board These devices, depending on the demand, controls the path of heated primary water either to the secondary heat exchanger (plate exchanger) or through to the central heating circuit. Diverter valves normally rest in central heating mode so it can dump excess heat on the central heating circuit. To test a diverter valve: 240 V LIVE TEST   Central heating on: Check for correct voltage at end of wiring harness on motorised valve head (printed circuit board end – ensure correct colour wires are tested) Hot water on: Check for correct voltage at end of wiring harness on motorised valve head (printed circuit board end – ensure correct colour wires are tested) Note: Should correct voltages be present at respective connections, but still not functioning correctly on a hot water or central heating demand, then the diverter valve may need replacing. Common faults: On a central heating demand with the boiler firing but reaching up to temperature rapidly and shutting down with the pump running on, the diverter valve will be stuck in the hot water mode and needs replacing. On a hot water demand with the hot water temperature remaining cold but a temperature rise through the central heating flow pipe, the diverter valve will be stuck in the central heating mode. On a hot water demand with the hot water temperature remaining warm not hot, with a temperature rise through the central heating flow pipe, the diverter valve will be letting by….

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