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UNIT 91 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
91-1) What are the most common types of refrigeration system contaminants
introduced because of improper installation?
91-2) How does carbon affect a system?
91-3) What effect does the presence of non-condensables have on a system?
91-4) What system condition is indicated by copper plating?
91-5) What are the most common sources of refrigeration system contamination?
91-6) Explain how contaminants from a previous compressor failure can cause a
replacement compressor to fail.
91-7) What is the purpose of collecting system baseline performance data?
91-8) List the system characteristics that are checked when taking system baseline
performance.
Compressor Data: suction pressure, suction temperature, discharge
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Condenser Data: temperature of air or water in, temperature of air or
water out, condenser flow in CFM or GPM, liquid line temperature
Evaporator Data (Including Metering Device): entering air wet bulb
temperature (for air coils), temperature of air or water in, temperature of
air or water out, evaporator flow in CFM or GPM, liquid line
temperature, suction line temperature
91-9) List the stages of system cleanup
The stages in cleaning up a system are
2. changing the contaminated compressor oil
4. performing any system modifications or repairs
6. evacuating and charging the system
91-10) Why does changing the compressor oil help clean up a contaminated system?
91-11) What is the difference between a regular filter drier and a cleanup filter drier?
91-12) Why should a cleanup filter drier always be used after performing a system
flush? Some of the particles loosened by the flushing procedure are not removed
91-13) Which refrigeration system components should not be flushed?
91-14) List the steps in flushing a system.
Recover the system refrigerant, disconnect the lines at the evaporator coil,
91-15) What are the two general types of oil acid tests available?
91-16) Why is it safer to cut out refrigeration components for removal rather than de-
braze them?
91-17) Why are suction line accumulators particularly vulnerable to system
contamination?
91-18) When retrofitting a CFC or HCFC system with a newer HFC refrigerant, why
is the HFC refrigerant charge usually less than the original factory charge?
91-19) Why is a good evacuation critical after performing a system cleanup?
91-20) Describe the correct way to loosen a mechanical fitting when removing a
refrigeration component.
91-21) Why should refrigerant from a compressor burnout be recovered into a separate
cylinder marked “contaminated?”
91-22) What factors are taken into consideration when sizing filter driers?
91-23) Why should suction line filter driers be removed after the system is clean?
