Air Conditioning Repair Air Conditioning Repair Preventive Maintenance and System Efficiency 2 — Questions and Answers
Question 1: What is the correct procedure for testing a dual-run capacitor on a residential AC unit?
- Discharge it, then test capacitance with a capacitor-rated multimeter (Correct answer)
- Test it while energized using a clamp meter
- Replace it whenever the unit is serviced regardless of readings
- Measure its resistance with a standard ohmmeter
Correct answer: Discharge it, then test capacitance with a capacitor-rated multimeter
A dual-run capacitor must be safely discharged before testing its capacitance with a meter rated for capacitor testing.
Question 2: Which measurement indicates proper lubrication is needed on older belt-drive blower motors?
- Motor running hot above its rated temperature or unusual squealing noise (Correct answer)
- Low static pressure in the duct system
- High delta-T across the evaporator
- Low suction pressure at the service valve
Correct answer: Motor running hot above its rated temperature or unusual squealing noise
Excessive heat or squealing from a belt-drive motor bearing signals inadequate lubrication and potential bearing failure.
Question 3: A technician measures the outdoor ambient temperature at 95°F. What is the expected normal operating range for high-side (discharge) pressure on an R-410A system?
- 380–420 PSIG (Correct answer)
- 150–175 PSIG
- 200–230 PSIG
- 450–500 PSIG
Correct answer: 380–420 PSIG
For R-410A at 95°F ambient, normal high-side (condensing) pressure is typically in the 380–420 PSIG range.
Question 4: What is the purpose of a condensate trap installed on an AC air handler?
- To prevent negative duct pressure from pulling sewer gases back through the drain line (Correct answer)
- To increase cooling efficiency
- To filter dirt from the condensate water
- To measure refrigerant charge
Correct answer: To prevent negative duct pressure from pulling sewer gases back through the drain line
A condensate trap creates a water seal that prevents negative static pressure in the air handler from breaking the drain flow and introducing odors or pathogens.
Question 5: During a maintenance check, the technician notices the outdoor fan motor is drawing more amps than its nameplate rating. What is the most likely cause?
- Failing motor bearings or a failing capacitor (Correct answer)
- Refrigerant overcharge
- Dirty evaporator coil
- Low suction pressure
Correct answer: Failing motor bearings or a failing capacitor
A motor drawing above nameplate amperage usually indicates worn bearings creating drag or a weak start/run capacitor failing to support the motor.
Question 6: What is the correct method for disposing of old compressor oil removed during system maintenance?
- Dispose of it as hazardous waste through an approved recycling or disposal facility (Correct answer)
- Pour it down a floor drain
- Mix it with fresh oil and reuse it
- Discard it in a standard trash receptacle
Correct answer: Dispose of it as hazardous waste through an approved recycling or disposal facility
Compressor oil from refrigeration systems is considered hazardous waste and must be disposed of through a licensed recycling or hazardous waste facility.
Air Conditioning Repair Air Conditioning Repair Preventive Maintenance and System Efficiency 2
What is the correct procedure for testing a dual-run capacitor on a residential AC unit?