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AIR CONDITIONING CERTIFICATION QUESTIONS WITH CORRECT SOLUTIONS, Exams of Refrigeration and Air Conditioning

University of OxfordRefrigeration and Air Conditioning

AIR CONDITIONING CERTIFICATION QUESTIONS WITH CORRECT SOLUTIONS . AIR CONDITIONING CERTIFICATION QUESTIONS WITH CORRECT SOLUTIONS

Typology: Exams

2024/2025

Available from 07/14/2025

Prof.Henshall
Prof.Henshall 🇬🇧

352 documents

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AIR CONDITIONING CERTIFICATION QUESTIONS WITH
CORRECT SOLUTIONS
What is the movement of heat through space called? - SolutionRadiation
A refrigerant release heat when - SolutionIt condenses
Why is it desirable for refrigerant in the suction line to be slightly
superheated? - SolutionTo insure liquid refrigerant does not enter the
compressor
A 30 pound cylinder of reclaimed R-22 refrigerant has been stored over
night at 70 degrees F. What should be the approximate pressure in the
cylinder? - Solution121 psig
14.7 psia( pouds per square inch absolute) is - SolutionApproximately 0
PSIG
What is the main fuction of an air condition condenser? - SolutionTo
remove heat from the refrigerant
Refrigerant R-134a vapor enters the condenser at 124 psig, 100 degrees
F. It leaves the condenser at 80 degreesF. What will be the approximate
pressure? - Solution124 psig (the pressure should not change entering or
leaving the condenser)
Which of the following CANNOT be used as a low ambient temperature
control? - SolutionCrankcase regulating valve
When testing the efficiency of a (10 seer are lower) air cooled
condenser, the refrigerant condensing temperature should be no more
than_______ higher than the entering air temperature -
SolutionApproximately 30 degrees F
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AIR CONDITIONING CERTIFICATION QUESTIONS WITH

CORRECT SOLUTIONS

What is the movement of heat through space called? - Solution Radiation A refrigerant release heat when - Solution It condenses Why is it desirable for refrigerant in the suction line to be slightly superheated? - Solution To insure liquid refrigerant does not enter the compressor A 30 pound cylinder of reclaimed R-22 refrigerant has been stored over night at 70 degrees F. What should be the approximate pressure in the cylinder? - Solution 121 psig 14.7 psia( pouds per square inch absolute) is - Solution Approximately 0 PSIG What is the main fuction of an air condition condenser? - Solution To remove heat from the refrigerant Refrigerant R-134a vapor enters the condenser at 124 psig, 100 degrees F. It leaves the condenser at 80 degreesF. What will be the approximate pressure? - Solution 124 psig (the pressure should not change entering or leaving the condenser) Which of the following CANNOT be used as a low ambient temperature control? - Solution Crankcase regulating valve When testing the efficiency of a (10 seer are lower) air cooled condenser, the refrigerant condensing temperature should be no more than_______ higher than the entering air temperature - Solution Approximately 30 degrees F

When testing the efficiency of a water cooled condenser, the refrigerant condensing temperature should be no more _____ higher than the leaving water temperature. - Solution 10 degrees F What does a temperature differential across a filter-drier indicate? - Solution Restricted filter-drier Which of the following symptoms would be indicative of an oil logged evaporator? - Solution Reduce heat transfer through the walls of the coil When using an electronic leak detecto, the sensor probe - Solution should be moved at approximately 1 inch per second Before a vapor / compression system is opened for service - Solution the refrigerant must be recovered using approved equipment What is the minimum vertical drop from the outlet of the condensate drain pan to the inlet of the P trap when the evaporator is ahead of the blower? - Solution 3 inches The temperature rise method of determining air volume CFM is mostly used with a/an; - Solution electric resistive heat air handler What is a sling psychrometer used to measure - Solution wet and dry bulb temperature A compressor is operating with a discharge pressure of 235.3 psig and a suction pressure of 35.3 psig. What is the compression ratio (pumping ratio)? - Solution 5:1 (235.3+14.7=250) and (35.3+14.7=50) so 250/5= What method does hot gas bypass refer to? - Solution Capacity control IF a TEV sensing bulb has lost of its charge, What effect would this have on the air conditioning system - Solution It would cause the low side pressure to decrease

When setting a high pressure cut-out on a R-22 system which has an air cooled condenser, the setting should be approximately _______. - Solution 395 psig. The cutout must be set approximately 50% above the operating pressure When is the installation of a "P" trap mandatory in a drain line? - Solution When the evaporator coil is located on the negative side of the blower. A pump-down system should have a (an); - Solution liquid receiver. What is a liquid receiver used for? - Solution To store liquid refrigerant The oil pressure safety switch is operated by _________. - Solution the difference between crankcase pressure and oil pump pressure Which of the following is the opening force on a water regulating valve being used on a water cooled condenser? - Solution The high side pressure What is the "G" terminal used for on a heating and cooling thermostat? - Solution The blower relay. When should a thermostatic expansion valve with an external equalization line be used? - Solution When the evaporator has a pressure drop that causes more than 2°F saturation temperature change An thermal expansion valve that is stuck wide open will cause ___________. - Solution a flooded evaporator A properly functioning condenser should always have ______________ leaving the condenser; - Solution sub-cooled, liquid Tube within a tube, shell and coil, and shell and tube are all types of: - Solution water cooled condensers.

What is one of the main reasons that reciprocating compressors are not 100% efficient? - Solution clearance volume Where is an open drive compressor most likely to develop a refrigerant leak? - Solution shaft seal The automatic expansion valve (AEV) maintains a constant ______ in the evaporator. - Solution pressure Short cycling during pump down can be caused by: - Solution a leaking compressor suction valve What is a crankcase heater used to prevent? - Solution Refrigerant migration to the compressor crankcase during the off-cycle. The type of compressor that allows access to the internal components is the _______. - Solution reciprocating semi-hermetic What do water cooling towers require? - Solution Periodic de-scaling When a compressor service valve is in the cracked position, which port is closed? - Solution None are closed . When the service valve is in the cracked position all ports are open Why must an oil separator be kept warm? - Solution To prevent refrigerant from condensing in the separator during the off cycle. Which part of the system stores refrigerant until it is needed in the evaporator: - Solution the receiver Which part of the system prevents liquid from entering the compressor: - Solution the accumulator

dirty condenser coil - Solution - high operating pressures If the metering device malfunctions and gets stuck in the closed position, the compressor could overheat. - Solution 'True'. Superheat occurs in the condenser as well as the evaporator. - Solution True' If a compressor has a partially shorted winding, it could run for a while, overheat, and shut off. - Solution 'True' When would it be beneficial for a technician to pump a system down before servicing? - Solution when the thermostatic expansion valve needs to be changed To accurately add refrigerant to a system, a condenser ambient temperature of ____°F should be simulated. - Solution 95 Why does a high efficiency condenser operate at much lower head pressures? - Solution The high efficiency condenser has a larger surface area and uses modern alloy surfaces and fins. This allows the condenser to reject heat much more rapidly. This brings temperature down and reduces the head pressure. What type of metering device do you find on a high efficiency system? - Solution High efficiency systems use a TXV rather than a fixed bore device. How do you determine EER? - Solution It is the amount of output in BTUH divided by the number of input in Watts. 36000 Btuh / 4000 W = EER of 9 How do you determine EER? - Solution It is the amount of output in BTUH divided by the number of input in Watts. 36000 Btuh / 4000 W = EER of 9

What is SEER? - Solution It is an efficiency rating system that takes includes the startup and shutdown cycles. When measuring high voltage, what are the parameters for 115V and 208V/230V? - Solution It is ± 10% of the rated voltage. For 115V, that would be 104V - 126V. For 208V/230V that would be 187V - 253V What is the approach temperature? - Solution Also known as temperature split. It is the difference in temperature between heat exchange mediums. Example would be the temp difference between the indoor coil and the return air for an AC system. What is a service valve? - Solution It is a valve that can be used to isolate the system for service. It is usually manually operated. Why should you use a short gauge hose on the high side? - Solution If you used a long hose, the amount of liquid refrigerant in the hose may be enough to affect the system charge and gauge readings. What should be the highest discharge line temperature? - Solution It should not exceed 220°F. What situations can cause high compression ratios? - Solution They can result from low suction pressures, high condensing pressures, or combination of both. If no crankcase heat is at the compressor, what may happen to the refrigerant charge? - Solution The charge may migrate to the crankcase. Reducing the CFM through the evaporator will cause the amperage draw of the compressor to - Solution decrease Where is the correct location for a sight glass in order to check the charge? - Solution At the metering device on the condenser side.