HVAC Compressors and Condensing Units 3

Question 1

What is the difference between a semi-hermetic and a fully hermetic compressor?

Accepted Answer

Semi-hermetic compressors have bolted serviceable housings while fully hermetic compressors are welded shut

Answer

Semi-hermetic compressors have bolted-together housings that can be disassembled for service, while fully hermetic compressors are welded closed and not field-repairable.

Question 2

What is the typical cause of high head pressure on an air-cooled condensing unit?

Accepted Answer

Dirty or blocked condenser coil restricting airflow

Answer

A dirty or blocked condenser coil reduces airflow and the coil's ability to reject heat, causing condensing pressure and temperature to rise.

Question 3

What does low suction pressure typically indicate in a refrigeration system?

Accepted Answer

Restricted metering device or low refrigerant charge

Answer

Low suction pressure commonly results from a restricted metering device limiting refrigerant flow into the evaporator, or from a low refrigerant charge.

Question 4

Which condition can cause a compressor to draw excessive amperage (high amps)?

Accepted Answer

High suction and discharge pressures due to an overcharge or condenser issue

Answer

High suction and discharge pressures increase the pressure differential the compressor must overcome, raising amperage draw beyond normal levels.

Question 5

What is 'oil logging' in an evaporator coil?

Accepted Answer

Refrigerant oil accumulating in the evaporator coil and reducing heat transfer

Answer

Oil logging occurs when refrigerant oil accumulates in the evaporator coil, coating heat transfer surfaces and reducing the system's cooling efficiency.

HVAC - Heating, Ventilation, and Air Conditioning Practice Test

HVAC - Heating, Ventilation, and Air Conditioning Practice Test

HVAC Compressors and Condensing Units 3