Air Conditioning Repair Electrical Systems and Controls 4

Question 1

A dual-run capacitor on a condenser unit is labeled 45+5 MFD. What components does it serve?

Accepted Answer

Compressor run winding and outdoor fan motor

Answer

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.

Question 2

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?

Accepted Answer

Replace the fuses with correctly rated 30-amp fuses

Answer

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.

Question 3

A technician measures capacitor capacitance and finds it reads 38 MFD on a capacitor rated 45 MFD ±6%. Is the capacitor within tolerance?

Accepted Answer

No, it is below the allowable tolerance range

Answer

±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.

Question 4

What does the term 'minimum circuit ampacity' (MCA) on an equipment nameplate indicate?

Accepted Answer

The minimum wire ampacity required for the supply conductors

Answer

MCA specifies the minimum current-carrying capacity the supply wiring must have to safely power the unit under operating conditions.

Question 5

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?

Accepted Answer

Open run capacitor for the fan motor

Answer

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.

Air Conditioning Repair Practice Test

Air Conditioning Repair Practice Test

Air Conditioning Repair Electrical Systems and Controls 4