RSES Troubleshooting 5

Question 1

A rooftop packaged unit condenser fan motor fails in summer. What will happen to system operation if ignored?

Accepted Answer

Head pressure will rise, potentially tripping the high-pressure switch or damaging the compressor

Answer

Without condenser airflow, heat rejection fails, causing discharge pressure to rise until the high-pressure cutout trips or the system sustains damage.

Question 2

A technician recovers refrigerant from a system, then pulls a deep vacuum and the vacuum rises rapidly when the pump is isolated. What does this indicate?

Accepted Answer

There is a leak or residual moisture in the system

Answer

A rising vacuum after pump isolation indicates either a system leak (air entering) or moisture boiling off, both requiring remediation before recharge.

Question 3

What is the significance of measuring temperature difference (TD) across an evaporator coil during troubleshooting?

Accepted Answer

TD measures airflow adequacy and coil heat transfer effectiveness

Answer

The temperature difference between air entering and leaving the evaporator reflects airflow volume and coil efficiency; abnormal TD suggests airflow or coil problems.

Question 4

A refrigeration system uses a capillary tube metering device and is suspected of being undercharged. How is the charge typically verified on this type of system?

Accepted Answer

By weighing in the exact factory charge after a complete evacuation

Answer

Capillary tube systems are critically charge-sensitive and are best charged by weighing the exact factory specification into an evacuated system.

Question 5

During troubleshooting, a technician finds that the contactor coil is energized but the compressor does not start. The compressor hums briefly then the internal overload trips. What is the most likely cause?

Accepted Answer

Single-phasing (loss of one leg of power) or failed start components

Answer

A compressor that hums but fails to start and trips its overload is typically experiencing single-phasing or has failed start capacitors/relays preventing proper motor starting.

(RSES) Refrigeration Service Engineers Society Certification Practice Test

(RSES) Refrigeration Service Engineers Society Certification Practice Test

RSES Troubleshooting 5