CFESA Electrical and Mechanical Systems 5 — Questions and Answers
Question 1: A commercial gas range's igniter glows orange but the burner fails to light. What does this most likely indicate?
- The igniter is too hot and needs to cool down
- The igniter is weak and not reaching the minimum current threshold to open the gas valve (Correct answer)
- The gas valve is stuck open
- The thermocouple is generating excess voltage
Correct answer: The igniter is weak and not reaching the minimum current threshold to open the gas valve
Hot surface igniters must reach a specific current draw (typically 3-4 amps) to signal the gas valve to open; a weak igniter glows but doesn't draw enough current.
Question 2: What is the function of a run capacitor in a single-phase PSC (permanent split capacitor) motor used in commercial refrigeration?
- To start the motor from rest by providing a phase shift
- To remain in the circuit continuously, improving motor efficiency and power factor during operation (Correct answer)
- To boost voltage during high-load conditions
- To provide short-circuit protection for the motor windings
Correct answer: To remain in the circuit continuously, improving motor efficiency and power factor during operation
A run capacitor stays connected during normal operation, creating a phase shift in the auxiliary winding that improves motor efficiency and reduces current draw.
Question 3: During installation of a commercial oven, the technician measures 208V between L1 and L2, 208V between L2 and L3, but only 120V between L1 and L3. What does this indicate?
- The oven requires a neutral wire and this is normal
- An open or high-resistance fault on L3 in the supply panel or connections (Correct answer)
- The oven is properly connected to a single-phase supply
- Phase rotation is reversed and must be corrected
Correct answer: An open or high-resistance fault on L3 in the supply panel or connections
Unequal three-phase voltage readings like this pattern indicate a problem with one supply leg — an open connection or bad breaker on L3.
Question 4: What is the correct procedure before using an ohmmeter to test a component in a live commercial food equipment circuit?
- Set the meter to AC volts first, then switch to ohms
- De-energize the equipment, lock out/tag out, and discharge any capacitors before measuring resistance (Correct answer)
- Take resistance readings with the equipment running to get accurate values
- Remove only the fuse nearest to the component being tested
Correct answer: De-energize the equipment, lock out/tag out, and discharge any capacitors before measuring resistance
Ohmmeter readings are invalid and dangerous in a live circuit; LOTO and capacitor discharge are mandatory safety steps before resistance testing.
Question 5: A commercial walk-in cooler evaporator fan motor hums but does not start. When the blade is given a manual spin, it runs normally. What component is most likely faulty?
- The run capacitor
- The start capacitor or start winding (Correct answer)
- The overload protector
- The motor's run winding
Correct answer: The start capacitor or start winding
If a motor hums but won't self-start and runs fine once manually started, the starting mechanism (start capacitor or start winding) has failed.
Question 6: Which mechanical failure in a commercial mixer would cause oil to leak from the attachment hub area?
- A broken bowl lift spring
- A worn or damaged beater shaft oil seal (Correct answer)
- A misaligned bowl support bracket
- A stripped planetary gear
Correct answer: A worn or damaged beater shaft oil seal
The beater shaft oil seal prevents gear oil from migrating down the shaft and escaping at the attachment hub; a worn seal allows oil to leak at that point.
Question 7: When performing a load test on a commercial food equipment power circuit, what does a significant voltage drop between the panel and the equipment indicate?
- The equipment is drawing below rated amperage
- Excessive resistance in the supply conductors, connections, or breaker due to loose or corroded contacts (Correct answer)
- The supply transformer is undersized
- Normal voltage variation within acceptable tolerance
Correct answer: Excessive resistance in the supply conductors, connections, or breaker due to loose or corroded contacts
Voltage drop under load reveals high resistance in the circuit path — commonly caused by loose terminals, corroded connections, or an undersized or failing circuit breaker.
CFESA Electrical and Mechanical Systems 5
A commercial gas range's igniter glows orange but the burner fails to light.
What does this most likely indicate?