Identify the type of Thermal Switch that is Normally Closed.

• A. Flow Switch N.O.
• B. Thermal Switch N.C.
• C. Timed Contact N.O.T.O.
• D. Control Transformer Dual Voltage

Answer: (B)

The choice indicating the Thermal Switch that is Normally Closed is correct because a Normally Closed (N.C.) thermal switch maintains continuity in the circuit until a specified temperature is reached. When the temperature exceeds the set point, the switch opens, breaking the circuit and stopping the flow of electricity. This behavior is particularly useful in applications where continuous operation is desired until a critical temperature is detected, thus providing a safeguard against overheating.

In contrast, the other options either do not represent thermal switches or describe configurations that operate differently. For example, a Normally Open (N.O.) switch allows current to flow until the switch is triggered by a temperature change, which is contrary to the requirement. The Timed Contact option refers to a device that operates based on a timing mechanism rather than temperature, and the Control Transformer option relates to voltage regulation and does not involve temperature at all. Therefore, the emphasis on temperature regulation and the functional nature of the N.C. switch makes it the appropriate choice for identifying the thermal switch that is ordinarily closed.