• May 31, 2020
  • CCST

Certified Control System Technicians (CCSTs) calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables.

CCST question

A control system technician has been requested to design and install a circuit for an exhaust fan in a nonhazardous process location that is protected against electrical overload and for which the operator will be able to reset the circuit if it trips.

A. fuse
B. fusible link
C. thermal-magnetic circuit breaker
D. conditioning power supply

CCST Answer

The correct answer is C, thermal-magnetic circuit breaker. Both a fuse and a fusible link can be used to break the circuit in an over-current situation, but fuses and fusible links are not resettable. They must be replaced once tripped.

A conditioning power supply, while able to remove fluctuations in voltage and power output to the circuit, is not able by itself to disconnect a circuit in case of short circuits or electrical surges.

Reference: Goettsche, L.D. (Editor), Maintenance of Instruments and Systems, Second Edition, ISA, 2005.

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