Rule of Thumb for Thermocouple Installation

Thermocouple Extensions

• 1

  Determine the thermocouple type. The type determines which of the device̵7;s leads are positive or negative. For example, a Type J thermocouple has a positive lead made from an iron alloy, and a negative lead made from a copper and nickel alloy.

• 2

  Obtain a thermocouple extension wire. These are wires used to lengthen the sensor̵7;s leads. The wire must match the type being used, so a Type K can only use Type K extension wire, for example.

• 3

  Attach the thermocouple̵7;s positive lead to the positive extension wire. Likewise, attach the sensor̵7;s negative lead to the negative extension. The leads may be color coded to make the connections easier. For instance, the thermocouple̵7;s positive lead and the positive extension wire may both be white. Their negative sides may be colored red.

General Installation

• 4

  Turn the appliances off, and shut off the power before installation. For furnaces, turn the gas lines off.

• 5

  Obtain separate thermocouples for each appliance or instrument. For two devices, use a dual thermocouple. Do not use connect a single sensor to two devices, for example, because the reading may be inaccurate.

• 6

  Install the thermocouple in an area away from AC power lines. This is because they may pick up noise from the wires, which will interfere with their measurement.

• 7

  Install the thermocouple vertically in high temperature environments. This helps to prevent its protective tubing or sheath from sagging.

• 8

  Avoid direct contact between a flame and the thermocouple̵7;s tubing or sheath. Direct contact shortens the tubing̵7;s life. Route thermocouple wires away from ignition devices, such as spark plugs or distributors, to help maintain the sensor̵7;s accuracy.