CARO Refrigeration Controls and Instrumentation

Question 1

What is the primary purpose of a high-pressure cutout switch in a refrigeration system?

Accepted Answer

To shut down the compressor when discharge pressure exceeds a safe limit

Answer

A high-pressure cutout switch protects the compressor and system by automatically shutting down the compressor when discharge pressure rises above a preset safe limit.

Question 2

Which instrument is used to measure both suction and discharge pressures simultaneously on a refrigeration system?

Accepted Answer

A manifold gauge set

Answer

A manifold gauge set has two gauges — a low-side (blue) for suction pressure and a high-side (red) for discharge pressure — allowing both readings at the same time.

Question 3

What does a solenoid valve do in a refrigeration control circuit?

Accepted Answer

Controls refrigerant flow by opening or closing electrically

Answer

A solenoid valve is an electrically operated valve that opens or closes to control the flow of refrigerant in response to an electrical signal from the control system.

Question 4

A thermostatic expansion valve (TXV) senses which two conditions to regulate refrigerant flow?

Accepted Answer

Evaporator outlet temperature and suction pressure

Answer

The TXV uses a sensing bulb at the evaporator outlet and an external equalizer sensing suction pressure to maintain a constant superheat and regulate refrigerant flow.

Question 5

What is the function of an oil pressure safety switch on an ammonia compressor?

Accepted Answer

To shut down the compressor if oil pressure falls below a safe minimum

Answer

The oil pressure safety switch monitors lubrication oil pressure and trips the compressor off if pressure drops below the minimum required to protect compressor bearings.

CARO - Certified Assistant Refrigeration Operator Practice Test

CARO - Certified Assistant Refrigeration Operator Practice Test

CARO Refrigeration Controls and Instrumentation