Thermo Electric FSD – Flashcards
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| Thermo Electric Valves KEYWORDS |
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| Electrically operated valve. coil creates magnetic field that holds gas valve in open position No electrical supply will cause a spring to close the valve |
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| Thermo Electric Valves Where Found ? |
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| C/H Boilers ,W.A.U as part of composite valve Water Heaters, fires and cookers |
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| Thermo Electric Valves TESTS |
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| Should fail safe within 60sec (audible click) |
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| Thermoelectric Valves FAULTS |
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| Fails to shut off within time period. Fails to hold open (also Thermocouple could be at fault) |
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| Thermoelectric Valves WITH INTERRUPTER |
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| Thermocouple to the valve will be interrupted by a safety device such as TTB or overheat This breaks the voltage circuit to the valve from thermocouple when a fault occurs Shuting the appliance down. |
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| Thermoelectric valve F.S.D Alternative names: thermocouple |
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| T he thermocouple tip, when heated by a flame, creates a small electric current which flows al the wire to an electromagnetic coil inside the valve. The coil generates a magnetic field which hold open the gas valve. If the flame is extinguished the thermocouple tip cools, the current and magnetic field disappear the valve springs shut, stopping gas flow. |
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| Testing a Thermoelectric valve |
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| Run the appliance until it reaches normal operating temperature. Achieve flame failure by turning off the gas supply at a suitable upstream isolation valve. Ensure the valve clicks out within the acceptable time limit. Ensure gas flow has been stopped (e.g. with a manometer downstream of the thermoelectric valve). For many appliances the maximum cut out time specified by British Standards is 60 seconds, but the appliance manufacturer may specify a different time. If click-out takes longer, or if gas continues to flow afterwards, the valve is faulty. If a valve takes less than ten seconds to click out then the thermocouple may be close to failure. Inspect the tip, wire and connections carefully for signs of burn-out, corrosion or damage. |
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| Interrupted thermoelectric valve Flame supervision device with secondary shut off Alternative name: interrupter (spelt “interruptor” by some suppliers) |
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| This device works in the same way as a thermoelectric valve with the addition of an electrical connection in series to an overheat thermostat or other safety device. If the safety device activates it opens the circuit, stopping current to the thermoelectric valve and shutting down the appliance. Test: as for thermoelectric valve. There is no means of simulating overheat conditions outside a specialist testing facility. |
