Electrical and Mechanical Systems Flashcards

A commercial gas range's igniter glows orange but the burner fails to light. What does this most likely indicate?

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.

What is the function of a run capacitor in a single-phase PSC (permanent split capacitor) motor used in commercial refrigeration?

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.

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?

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.

What is the correct procedure before using an ohmmeter to test a component in a live commercial food equipment circuit?

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.

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?

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.

Which mechanical failure in a commercial mixer would cause oil to leak from the attachment hub area?

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.

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?

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.