Compressor Systems Flashcards
7 cards from real RSES practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Compressor Systems flashcards as text
What is the purpose of a check valve installed in the compressor discharge line?
Answer: To prevent reverse rotation during the off cycle
A discharge check valve prevents high-pressure refrigerant from flowing backward through the compressor during the off cycle, which could cause reverse rotation and compressor damage.
A technician measures equal suction and discharge pressures on a running compressor. What is the most likely diagnosis?
Answer: Completely failed or broken compressor valves
Equal suction and discharge pressures on a running compressor indicate the compressor is not pumping, almost always caused by totally failed discharge and/or suction valves.
Which type of compressor is best suited for large-tonnage chiller applications requiring variable capacity with high efficiency?
Answer: Open-drive centrifugal compressor
Open-drive centrifugal compressors are used in large chiller applications because they provide high efficiency over a wide capacity range and are easily adapted to variable loads with inlet guide vanes.
What is the function of a crankcase heater on a compressor?
Answer: To prevent refrigerant migration into the crankcase oil during the off cycle
Crankcase heaters keep the oil warm during the off cycle to prevent refrigerant from migrating into and diluting the crankcase oil, which could cause oil foaming and bearing damage on startup.
What is 'liquid slugging' in a compressor, and what component failure can result?
Answer: Liquid refrigerant entering the compressor cylinder; can break valves and pistons
Liquid slugging occurs when liquid refrigerant enters the compressor cylinder; since liquid is incompressible, it can crack or shatter the valves, pistons, or connecting rods.
What is the recommended corrective action when a compressor oil pressure safety control trips?
Answer: Check oil level, inspect for refrigerant dilution, and inspect the oil pump before restarting
Before restarting after an oil pressure trip, technicians must verify the oil level, check for refrigerant dilution of the oil, and inspect the oil pump to identify the root cause.
In a parallel compressor rack system, what is the primary advantage of staging compressors on and off?
Answer: It matches system capacity to varying load while keeping running compressors near full load
Staging compressors allows the system to modulate total capacity while keeping each individual running compressor near its most efficient full-load operating point.