Compressor Operation and Maintenance Flashcards
7 cards from real CARO 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 Operation and Maintenance flashcards as text
What does a high-pressure cutout switch on a compressor do?
Answer: Shuts down the compressor when discharge pressure exceeds a safe setpoint
The high-pressure cutout stops the compressor before discharge pressure reaches levels that could open relief valves or damage equipment.
A compressor shows unusually low suction pressure. Which condition is the most likely cause?
Answer: A starved evaporator or very light refrigeration load
When little refrigerant boils off in the evaporator, the compressor pulls suction pressure down.
Before opening a compressor for internal maintenance, which step is required first?
Answer: Pump down, isolate, lock out/tag out, and verify the compressor is at zero pressure
Removing refrigerant, isolating the machine, applying lockout/tagout and checking for zero pressure protect the worker from energy and ammonia release.
Why is some superheat maintained in the suction gas entering a compressor?
Answer: To ensure only vapor and no liquid enters the compressor
Superheat means the gas is above its saturation temperature, so no liquid droplets remain to damage the compressor.
Which condition will most likely cause an excessively high compressor discharge temperature?
Answer: High compression ratio combined with high suction superheat
Large compression ratios and hot suction gas both raise the temperature of the gas leaving the compressor.
In an ammonia system, why is oil drained from the low points of vessels such as the receiver and oil pots?
Answer: Mineral oil is heavier than liquid ammonia and does not mix with it, so it settles at the bottom
Common refrigeration oils are denser than liquid ammonia and largely immiscible with it, so they collect at the bottom.
A compressor motor is drawing amperage above its full-load rating. Which is the most likely cause?
Answer: High suction pressure or high discharge pressure overloading the motor
Higher suction density or higher head pressure increases compressor work, which increases motor current.