UNIT 28 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
28-1) What chemicals should be inside a refrigeration system?
28-2) How are vacuum pumps rated?
28-3) What is the purpose of evacuating a refrigeration system?
28-4) What is a micron?
28-5) Explain how microns are used to measure vacuum.
28-6) What happens if noncondensables are left in the system?
28-7) What happens if moisture is left in the system?
28-8) Why does the presence of liquid water in a system slow down the evacuation
process?
28-9) What is considered a good vacuum level for a deep vacuum?
28-10) What are the two most common types of vacuum pumps?
28-11) How often should the vacuum pump oil be changed?
28-12) Why should only oil designed for vacuum pump operation be used in vacuum
pumps?
28-13) Where is the best place to connect a vacuum gauge?
28-14) Why is the vacuum scale on the compound gauge not used to measure deep
vacuum?
28-15) What is a vacuum?
28-16) What is a perfect vacuum?
28-17) Why should systems be tested for leaks prior to evacuation?
28-18) What is indicated if, during evacuation, the vacuum level stalls out around
2,000 microns and quits dropping?
28-19) What is indicated if, after evacuation, the vacuum level gradually rises to
atmospheric pressure?
28-20) What is indicated by milky vacuum pump oil?
28-21) What can be done to speed up evacuation?
28-22) How long does it take to pull a deep vacuum?
28-23) What is a multiple vacuum?
28-24) Why is it important to be able to isolate the vacuum gauge from the system after
evacuation?
28-25) Why should the vacuum pump isolation valve be closed before turning off the
vacuum pump?