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28 Cards in this Set
- Front
- Back
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The low pressure side of the system must not be pressurized to more than..
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The low side design pressure
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Name the six classes of leaks
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-standing leaks
-pressure dependent leaks -temperature dependent leaks -vibration dependent leaks -combination dependent leaks -cumulative microleaks |
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standing leaks?
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leaks that can be detected while the unit is at rest or off, including freezer evaporator coils warmed up by the defrost cycle
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Pressure dependent leaks?
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can only be detected as the system pressure increases
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temperature dependent leaks?
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associated with the heat of expansion
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vibration dependent leaks?
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only occur during the unit operation. mechanical strain from motion, rotation, refrigerant flow, or valve actuation
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combination dependent leaks
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two or more conditions to induce leakage
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cumulative microleaks
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leaks that are to small to detect with standard tools
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why would oxygen or compressed air never be used to pressurize a system?
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oxygen and oil will become unstable and may explode under pressure
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List some of the foreign matter that may enter a refrigeration system
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moisture, dirt, oil, nitrogen
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true or false: a vacuum pump can remover any type of foreign matter that enters a system
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false
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air in a refrigeration system causes which of the fallowing problems?
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copper plating
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the only two products that should be circulating in a refrigeration system are
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refrigerant and oil
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In order to remove moisture from a refrigeration system using a vacuum pump it must be in what state?
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vapor
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are the best vacuum pumps one stage or two stage?
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two stage
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name the two types of vacuum procedures used by technicians
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deep vacuum and triple evacuations
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what can be done to get water out from under the oil level in the compressor
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heat the compressor
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when evacuating a refrigeration system that has solenoid valves, what special procedure must be fallowed?
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the valves should either be opened manually or electrically
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what is todays most accurate type of deep vacuum gauge
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micron gauge
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How many microns are in 1 inch?
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25400
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Describe the method for cleaning up a system that has experienced motor burn
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-front seat the inoperative compressors service valves to isolate the compressor from the rest of the system. Recover the refrigerant from the inoperative compressor and remove it. Install replacement compressor.
-Take sample of oil from the replacement compressor. Seal it in a glass bottle for comparison purposes after the cleaning procedure is complete - with the compressor isolated(both service valves front seated) from the rest of the system, evacuate the compressor only, after evacuation open the compressor service valves and close liquid line valve -pump down system -inspect all components -clean and replace if nescessary |
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What is the advantage of using large gauge lines for evacuation?
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It is quicker
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Why is it important to change oil on a vacuum pump after each evacuation?
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Because the cleaner your oil is the better your vacuum pump is going to run
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Describe the meaning of a deep vacuum, and explain why it is important to reach and hold a deep vacuum when pulling on a vacuum on a system
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Deep vacuum is attained vacuum that is below 250 microns. It is important to reach and hold a deep vacuum because that tells you theres no non condensible gas or moisture left in the system
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list the main advantages of a microfoam leak detection solution over standard bubble solutions
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-standard bubble solution doesnt have the coagulants and wet adhesives the microfoam solutions do.
-will pit and corrode brass iron |
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What could an oily dust spot on a condenser of evaporator coil indicate?
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a leak
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Why should a condenser be covered with a sheet before leak checking it with an electronic leak detector?
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should be covered with a sheet to serve as a barrier against any outside air movement before using an electronic leak detector
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Leaks that occur only when the unit is in opperation are what kind of leaks?
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vibration dependent leaks
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