Florida Home Inspector Practice Test

What is the primary function of a thermocouple in a gas appliance?

1. Ignite the gas

2. Confirm flame presence

3. Measure temperature

4. Control gas flow

The correct answer is: Confirm flame presence

The primary function of a thermocouple in a gas appliance is to confirm the presence of a flame. Thermocouples are crucial safety devices that consist of two wires made from different metals joined at one end. When heated, the connection produces a small voltage that indicates the temperature. In the context of a gas appliance, the thermocouple senses the heat from the flame. If the flame is present, the thermocouple generates sufficient voltage to keep the gas valve open, allowing the appliance to continue operating. If the flame goes out, the thermocouple will stop producing voltage, which leads to the shutdown of the gas flow to prevent the dangerous accumulation of unburned gas. Igniting the gas is not the role of the thermocouple; that function is typically handled by an igniter or pilot light system. While thermocouples do respond to temperature changes, their primary role is flame confirmation rather than direct temperature measurement. Additionally, the control of gas flow is managed by the gas valve in conjunction with the signals from the thermocouple; the thermocouple itself does not directly regulate gas flow but rather ensures it is safely allowed only when there is a flame present.