Refrigeration Controls and Instrumentation Flashcards
6 cards from real CARO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Refrigeration Controls and Instrumentation flashcards as text
What is the primary purpose of a high-pressure cutout switch in a refrigeration system?
Answer: To shut down the compressor when discharge pressure exceeds a safe limit
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.
Which instrument is used to measure both suction and discharge pressures simultaneously on a refrigeration system?
Answer: A manifold gauge set
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.
What does a solenoid valve do in a refrigeration control circuit?
Answer: Controls refrigerant flow by opening or closing electrically
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.
A thermostatic expansion valve (TXV) senses which two conditions to regulate refrigerant flow?
Answer: Evaporator outlet temperature and suction pressure
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.
What is the function of an oil pressure safety switch on an ammonia compressor?
Answer: To shut down the compressor if oil pressure falls below a safe minimum
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.
What does a pressure-temperature (PT) chart help a refrigeration operator determine?
Answer: The saturation temperature corresponding to a measured refrigerant pressure
A PT chart lists the corresponding saturation temperature for each pressure of a given refrigerant, allowing operators to determine if the system is operating at the correct conditions.