A standing pilot gas valve with 100% shut-off means what?

A standing pilot gas valve with 100% shut-off signifies that it completely blocks the flow of gas to both the pilot light and the main burners when it is in the off position. This is a crucial safety feature, ensuring that no gas is present in the combustion system when the furnace is not in operation, thus preventing any potentially hazardous situations such as gas leaks or unlit pilot flames.

When the valve is activated to allow gas flow, it will enable gas to reach both the pilot and the main burners, facilitating the ignition and operation of the furnace. This aspect is essential for reliable furnace performance, as it ensures that the burner system can be ignited safely and efficiently. Understanding this mechanism is vital for diagnosing issues with gas valves and for ensuring safe operation in HVAC systems.