Thermocouple function
The latest gas patio heaters use multifunctional controls incorporating a thermocouple linked to an electromagnetic valve . A thermo-electric gas valve used in patio heaters operate via a solenoid valve, instead of electric operation it is heated via a thermocouple.
Thermocouple output is sufficient to hold the valve open when operating normally. To lift the valve from its seating a manual valve is required. By turning the patio heater gas control valve the gas will enter the pilot to allow the piezo ignitor spark to light the pilot. The pilot light will energise the electro-magnetic unit to open the patio heater gas control valve. The voltage can be measured in millivolt range via a multimeter set.
A patio heater that fails to open the gas chamber or extinguishes the pilot when the gas control knob is turned to full could be caused by a worn thermocouple. It is worth checking the electromagnetic valve when replacing a thermocouple on the patio heater.
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