A gas shut off valve can be found in most modern gas appliances.
Furnace gas shut off valve.
A 24 vac transformer or the thermopile powers the main valve.
In order to ensure safety when working on other parts of the furnace the shut off valve stops the flow of oil hot water or other type of material that the furnace uses to create the heat.
You will occasionally have to replace the gas shut off valve or thermocouple as it is also called.
Turn the handle perpendicular with the pipe to close the valve and parallel to open the valve.
Most service valves are single lever ball valves.
The watts 201 5 valve shown will shut off the gas supply if water temperature exceeds 210 f.
Details about this gas fired water heater automatic gas shutoff valve are at automatic gas water heater shutoff temperature operated gas supply shutoff for water heaters watts 210 5 series.
The shut off valve stands in between the oil supply and the actual furnace itself.
They are designed to close the gas supply if the pilot light flame does not come on or if it is extinguished for some reason.
Local shut off valves local shutoff valves have handles that limit the flow of gas to a specific appliance.
Visual signs of lp gas leakage at an appliance gas valve.
Again handle parallel to the line means gas is flowing perpendicular means it s cut off.
Ultimately the thermocouple acts as a safety mechanism that prevents gas buildup within the home.
As a result this cuts off the supply of gas to the pilot light.