Electrical Systems 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 Systems and Controls flashcards as text
A dual-run capacitor on a condenser unit is labeled 45+5 MFD. What components does it serve?
Answer: Compressor run winding and outdoor fan motor
A dual-run capacitor has two capacitance values in one can: the larger value (45 MFD) serves the compressor run winding and the smaller (5 MFD) serves the condenser fan motor.
During an electrical inspection, a technician notices the disconnect box at the outdoor unit contains a fused disconnect with 40-amp fuses, but the unit nameplate specifies a maximum overcurrent protection of 30 amps. What action is required?
Answer: Replace the fuses with correctly rated 30-amp fuses
Overcurrent protection must not exceed the manufacturer's maximum rating; 40-amp fuses must be replaced with 30-amp fuses to comply with NEC and nameplate requirements.
A technician measures capacitor capacitance and finds it reads 38 MFD on a capacitor rated 45 MFD ±6%. Is the capacitor within tolerance?
Answer: No, it is below the allowable tolerance range
±6% of 45 MFD gives an acceptable range of 42.3–47.7 MFD; 38 MFD is below this range and the capacitor must be replaced.
What does the term 'minimum circuit ampacity' (MCA) on an equipment nameplate indicate?
Answer: The minimum wire ampacity required for the supply conductors
MCA specifies the minimum current-carrying capacity the supply wiring must have to safely power the unit under operating conditions.
A technician finds the compressor starts but the outdoor condenser fan does not run. Voltage at the fan motor terminals reads 240V. What is the most likely cause?
Answer: Open run capacitor for the fan motor
Voltage present at the motor with no rotation points to an open run capacitor, which prevents the motor from developing the torque needed to start.
Which NEC article specifically covers the installation of air conditioning and refrigerating equipment?
Answer: Article 440
NEC Article 440 specifically addresses air conditioning and refrigerating equipment, including hermetic refrigerant motor-compressors.
A technician is troubleshooting an air handler that blows warm air in cooling mode. The compressor and condenser fan are running. What electrical component failure could cause this symptom?
Answer: Open circuit in the reversing valve solenoid (heat pump)
On a heat pump, an open reversing valve solenoid coil prevents the valve from switching to cooling mode, causing the system to deliver warm air.