CRST Electrical Systems & Controls Flashcards
6 cards from real CRST practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CRST Electrical Systems & Controls flashcards as text
Which wiring method is required for refrigeration equipment in a damp or wet location per the NEC?
Answer: THWN wire in liquid-tight flexible metal conduit or equivalent wet-rated method
NEC requires wet-location rated conductors (such as THWN) and appropriate conduit methods like liquid-tight flexible metal conduit in damp or wet locations.
What is the purpose of a defrost timer in an electric defrost refrigeration system?
Answer: Initiate defrost cycles at set intervals by energizing defrost heaters and de-energizing the compressor
A defrost timer initiates defrost at programmed intervals, switching off the compressor and energizing electric heaters to melt frost accumulation on the evaporator coil.
What reading on a digital multimeter indicates an open winding in a compressor motor?
Answer: OL (overload / infinite resistance)
An OL (overload) reading on the resistance function indicates infinite resistance, meaning the winding conductor is broken (open circuit).
What is the minimum wire gauge typically required for a 240V, 30-amp refrigeration circuit per NEC?
Answer: 10 AWG copper
NEC requires 10 AWG copper conductors to safely carry 30 amps at 240V with appropriate ampacity and voltage drop.
In a refrigeration control diagram, what component is indicated by the letters 'EPR'?
Answer: Evaporator pressure regulator
EPR stands for Evaporator Pressure Regulator, a back-pressure valve that maintains a minimum evaporator pressure to prevent freezing in multi-temperature systems.
What is the purpose of a ground fault circuit interrupter (GFCI) outlet near refrigeration equipment in a food service setting?
Answer: Protect personnel from electric shock by detecting small ground fault currents
A GFCI detects imbalances as small as 5mA between hot and neutral conductors, indicating current leaking to ground, and trips within milliseconds to prevent electrocution.