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UNIT 24 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
24-1) What are the two major functions of refrigerant piping?
24-2) What affect does oil have on a system’s coils?
24-3) What problems are caused by oversized suction lines?
24-4) What problems are caused by undersized suction lines?
24-5) What can be done to prevent refrigerant from being drained or migrating back
to the compressor during the off cycle?
24-6) Why is it important to keep the oil level balanced between parallel
compressors?
24-7) What is liquid slugging?
24-8) How is the maximum pressure drop for a suction line determined?
24-9) Which piping pressure drop has the greatest effect on the compressor’s
compression ratio?
24-10) What are some differences between piping practices for air-conditioning
systems and piping practices for commercial refrigeration systems?
24-11) Why are suction risers sized differently for systems with capacity control than
for systems without capacity control?
24-12) Why are oil lifts needed in tall vertical refrigerant risers?
24-13) What is the most common range for minimum velocities in a horizontal line
carrying refrigerant vapor?
24-14) What is the most common range for minimum velocities in a riser carrying
refrigerant vapor?
24-15) Why is refrigerant oil flow through the liquid line not a problem?
24-16) What two factors affect the hot gas line size?
24-17) What are the two common reasons the suction line is insulated?
24-18) Why may the liquid line need to be insulated?
24-19) Why might the hot gas line need to be insulated?
24-20) How can flash gas be spotted in a liquid line?
24-21) What would be the pressure drop due to the weight of refrigerant in a 30-foot
tall liquid line containing R 410A refrigerant at 100°F?
24-22) If the condenser pressure of the above system is 300 psig, how much
subcooling will be required to offset the pressure drop created by the vertical
lift?
24-23) According to Figure 24-31 what would be the recommended support spacing
for 2 1/8 inch type L copper pipe?
24-24) Use Figure 24-25 to determine the refrigerant velocity through a 7/8” suction
24-25) Use Figure 24-13 to determine the total equivalent length of a 50 foot section
of 1 3/8” line with four 90° elbows and 1 angle valve.
24-26) An engineer wishes to select a suction line that will have a maximum pressure
drop which is equivalent to a 2°F saturation temperature drop. What would be
the pressure drop for an R-134a system operating with a 0°F saturation
temperature?
24-27) What pressure drop should the engineer use on the nomograph if the
equivalent length for the suction line in the above system is 75feet?
24-28) What is considered a long line application for residential air conditioning?
24-29) List the system modifications that need to be made for a long line residential
air conditioning application.
24-30) What is the minimum recommended velocity for a 2 5/8 inch suction riser in a
low temperature system using R-22?
