Electrical Components and Controls Flashcards
7 cards from real Air Conditioning Repair practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Components and Controls flashcards as text
What is the primary function of a crankcase heater on a compressor?
Answer: To prevent refrigerant migration and oil dilution during the off cycle
Crankcase heaters keep the compressor oil warm so refrigerant does not migrate into the crankcase and dilute the lubricant during shutdown.
A time-delay relay in an AC control circuit is set for 5 minutes. What is its purpose?
Answer: To prevent short-cycle compressor restarts
Time-delay relays prevent short cycling by enforcing a minimum off time before the compressor can restart, protecting it from pressure equalization issues.
When testing a capacitor with a capacitance meter, a reading of zero indicates what condition?
Answer: The capacitor is open (internally broken)
A zero capacitance reading means the internal element is open and the capacitor cannot store a charge.
A compressor is wired to a 208/230V disconnect. Which wire gauge is required for a 30-amp circuit per NEC?
Answer: 10 AWG
NEC requires 10 AWG copper conductors for a 30-amp circuit at standard ambient temperatures.
What type of transformer is typically used to supply 24V control voltage in a residential split system?
Answer: Step-down transformer
A step-down transformer reduces line voltage (120V or 240V primary) to 24V AC for the low-voltage control circuit.
A technician finds a blown 3-amp control fuse repeatedly. What is the correct diagnostic approach?
Answer: Disconnect control wiring sections to isolate the short before replacing the fuse
Isolating sections of the control circuit identifies the shorted wire or component causing the overcurrent before replacing the fuse.
What does a locked-rotor amperage (LRA) rating indicate on a compressor nameplate?
Answer: The inrush current drawn when the motor first starts
LRA is the high initial current drawn by a stalled or starting motor before it reaches operating speed.