Compressors and Condensing Units Flashcards
7 cards from real HVAC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Compressors and Condensing Units flashcards as text
What is the difference between a semi-hermetic and a fully hermetic compressor?
Answer: Semi-hermetic compressors have bolted serviceable housings while fully hermetic compressors are welded shut
Semi-hermetic compressors have bolted-together housings that can be disassembled for service, while fully hermetic compressors are welded closed and not field-repairable.
What is the typical cause of high head pressure on an air-cooled condensing unit?
Answer: Dirty or blocked condenser coil restricting airflow
A dirty or blocked condenser coil reduces airflow and the coil's ability to reject heat, causing condensing pressure and temperature to rise.
What does low suction pressure typically indicate in a refrigeration system?
Answer: Restricted metering device or low refrigerant charge
Low suction pressure commonly results from a restricted metering device limiting refrigerant flow into the evaporator, or from a low refrigerant charge.
Which condition can cause a compressor to draw excessive amperage (high amps)?
Answer: High suction and discharge pressures due to an overcharge or condenser issue
High suction and discharge pressures increase the pressure differential the compressor must overcome, raising amperage draw beyond normal levels.
What is 'oil logging' in an evaporator coil?
Answer: Refrigerant oil accumulating in the evaporator coil and reducing heat transfer
Oil logging occurs when refrigerant oil accumulates in the evaporator coil, coating heat transfer surfaces and reducing the system's cooling efficiency.
What is the purpose of a reversing valve in a heat pump condensing unit?
Answer: Reverse the direction of refrigerant flow to switch between heating and cooling modes
The reversing valve switches the refrigerant flow direction so the outdoor coil becomes the evaporator in heating mode and the condenser in cooling mode.
When replacing a compressor, why is it important to flush the refrigerant circuit?
Answer: To remove acid, carbon, and metallic debris left by a burned-out compressor
A burned-out compressor leaves acid, carbon deposits, and metallic particles in the system that can damage the new compressor if not removed by flushing.