Commercial Refrigeration For Air Conditioning Tech
Commercial Refrigeration for Air Conditioning Tech
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THE Test Bank for Commercial Refrigeration for Air Conditioning Technicians 3rd Edition Wirz
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Commercial Refrigeration for Air Conditioning Tech
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Commercial Refrigeration For Air Conditioning Tech
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Commercial Refrigeration for Air Conditioning Technicians
The difference between the evaporator temperature and the suction line temperature at the
coil outlet is:
a. superheat b. latent heat c. artificial heat d. extended heat
2- A typical evaporator temperature in an air conditioning system with 75° return air is:
a. 25° b. 40° c. 55° d. 75°
3...
Test Bank For Commercial Refrigeration for Air Conditioning Technicians 4th Edition by Dick Wirz
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Answers to Commercial Refrigeration QUIZ
Chapter 2 – Evaporators
Name: __MASTER______________ Number Right: ________ Scorer: ___________
1- The difference between the evaporator temperature and the suction line temperature at the
coil outlet is:
a. superheat b. latent heat c. artificial heat d. extended heat
2- A typical evaporator temperature in an air conditioning system with 75° return air is:
a. 25° b. 40° c. 55° d. 75°
3- A typical evaporator temperature in a 35° medium temperature walk-in system is:
a. 25° b. 40° c. 55° d. 75°
4- The TD (temperature difference) between evaporator and box temperature of a reach-in is:
a. 35° b. 20° c. 10° d. 5°
5- The greater the evaporator TD the ______ moisture is removed from the air passing over
the evaporator.
a. more b. less
6- If an evaporator has less than 5° superheat it is considered to be ____________.
a. starving b. flooding c. about normal
7- If an evaporator has more than 20° superheat it is considered to be ____________.
a. starving b. flooding c. about normal
8- If an evaporator has distributor tubes coming off the TEV distributor it is a ______________.
a. flooded evaporator.
b. cap-tube evaporator.
c. multiple-circuit evaporator.
d. stamped evaporator.
9- What is the temperature differential (cut-in to cut-out) of an air sensing thermostat in a
medium temperature refrigeration unit?
a. 2° b. 5° c. 10° d. 20°
10- A walk-in at 35° box temperature would require what type of defrost?
a. Off cycle
b. Planned defrost – clock only
c. Planned defrost with clock and electric heaters
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REVIEW for the Mid-Term Exam
Commercial Refrigeration
Review of Subjects:
1. Know why walk-ins are designed for slightly lower temperatures than reach-ins.
2. Know the approximate design box temperatures for:
a. Walk-in refrigerator ______, and walk-in freezer ______.
b. Reach-in refrigerator _____, and reach-in freezer _____.
3. Assume a walk-in refrigerator condensing unit and an A/C condensing unit are
installed next to each other. They both use R22 refrigerant. Compare their
condensing temperatures and their evaporator temperatures and understand
why.
4. Understand the transfer of heat: That heat goes to cold and that the greater the
temperature difference the faster the transfer of heat.
5. Know condenser splits of standard medium temperature refrigeration units and
the C/S for freezers.
6. Given the desired condenser split be able to determine the condensing
temperature for different ambient conditions.
7. Know what condensing temperature is and how to determine it given the head
pressure and the refrigerant type.
8. Understand the relationship between ambient temperature, condensing
temperature, head pressure, condenser split, and subcooling. Be able to
calculate one given the other.
9. Know what evaporator TD is and how it is determined.
10. What is the standard TD for walk-ins? What is the standard TD for reach-ins?
Understand the relationship between box temperature, evaporator temperature,
suction pressure, and superheat. Be able to calculate one given the other.
11. What is the relationship of moisture removal of an evaporator and its TD?
12. What is the standard superheat and subcooling of commercial refrigeration units
per T.R.O.T.?
13. What is the minimum allowable superheat and subcooling for most refrigeration
units? What is the maximum?
1
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14. Above what superheat would indicate a starving evaporator?
15. Below what superheat would indicate a flooding evaporator?
16. Below what subcooling would indicate an undercharged unit?
17. Above what subcooling would indicate an overcharged unit?
18. Be able to calculate superheat/subcooling from given pressures and
temperatures. Then be able to tell what that condition means in terms of
starving/flooding or an overcharge/undercharge.
19. Know how to take superheat and subcooling and how to calculate it given the
pressures, temperatures, and line temperatures.
20. Know the difference between off-cycle defrost, planned defrost, and planned
defrost with the addition of heat to defrost the evaporator. At what temperatures
are each used? (Above 36° is off-cycle, 35° is planned defrost, and below 33° is
planned defrost with heat added.)
21. What is a multi-circuited evaporator and what type of TEV must be used?
22. At what minimum condensing temperature is some type of head pressure control
needed?
23. How do HPR controls, fan cycle controls, and dampers control head pressure?
24. What is the normal condensing temperature maintained by water cooled units?
25. On a water cooled unit what is the difference between the temperature of the
leaving water and the condensing temperature?
26. On a water cooled unit does the incoming water enter the condenser where the
warm liquid refrigerant is leaving the condenser, or where the hot gas from the
compressor is entering the condenser?
27. What is clearance volume when associated with a reciprocating compressor?
28. What is volumetric efficiency?
29. Know how to determine a compressor’s compression ratio. Also, know which
raises the compression ratio more: a drop in suction pressure or a rise in head
pressure?
2
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