Diagnostic Troubleshooting Flashcards

A commercial steamer fails to build pressure. After checking the door gasket seal, the technician should inspect:

Answer: The water supply valve, water level probe, and heating elements

A steamer that won't build pressure likely has insufficient water (supply valve, level probe malfunction) or insufficient heat input (failed elements) — all must be checked.

On a commercial walk-in cooler, a technician finds the evaporator fan running but the evaporator coil is completely encased in ice. The defrost system should be checked for:

Answer: Failed defrost heaters, defrost timer/control, or defrost termination thermostat

A completely iced-over evaporator indicates the defrost cycle is not functioning; failed heaters, a stuck defrost timer, or a faulty termination thermostat are the likely causes.

A commercial convection oven heats unevenly — hot on one side and cool on the other. After confirming the fan operates, the technician should check:

Answer: Individual heating elements or burner sections for open circuits or uneven output

Uneven heating in a convection oven is often caused by a failed heating element or burner on one side; checking individual elements for open circuits isolates the faulty component.

A commercial deep fryer's oil is overheating well above the setpoint. After confirming the thermostat is calibrated, the technician should test:

Answer: The gas valve for proper closure when the thermostat is satisfied

If the thermostat is calibrated and the oil still overheats, the gas valve may be sticking open rather than closing when the thermostat is satisfied, causing continuous heating.

A commercial refrigerator's compressor hums but will not start. The most likely cause on a single-phase unit is:

Answer: Failed start capacitor or start relay

A humming but non-starting compressor on a single-phase unit typically indicates a failed start capacitor or start relay that is not providing the starting torque needed.

What diagnostic information does a pressure-temperature (P-T) chart provide to a refrigeration technician?

Answer: The saturation temperature of a refrigerant at a given pressure

A P-T chart correlates refrigerant pressure to its saturation (boiling/condensing) temperature, allowing technicians to determine evaporating and condensing temperatures from gauge readings.