Markings on Type S Thermocouples and lead wire colors
Cautions
PDFs
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Question: On the thermocouple terminal block of our Type S thermocouple, one screw is clearly labeled with a bright red ‘+’ and the other has a dark black ‘-‘. However, in thermocouple wire, the negative leg is always red (at least in the US). Could you please let me know if in the factory you connect the red to negative/black to positive controller input terminals, or if you correct for the labeling of the thermocouples, and have red to positive?
Answer: On our type S thermocouples (which we get from Europe) the "+" is marked with red and the "-" is marked with black. The lead wire we use (from the USA) is red for negative and black for positive. (this answer is true for non-European kilns). The worse that can happen if the thermocopule wires get reversed is that the control will read negative which will create a quick alarm condition.