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34 Cards in this Set
- Front
- Back
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Reciprocatingcompressor capacity is usually accomplished?
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Unloaders |
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The two basic categories ofchillers are: |
Absorption, Compression |
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Threetypes of compressors used for chillers are: |
Scroll, screw, Reciprocating |
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How is capacity control accomplished on a screw compressor? |
Slide valve |
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How is capacity control accomplished on the centrifugal compressor? |
Inlet Guide Vanes |
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What is the purpose of multiple passes in a chiller evaporator? |
Lower approach temperature |
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What compressors are used on low pressure chillers? |
Centrifugal |
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TXV metering devices are used on low pressure chillers. True or False? |
No. |
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What ls used to remove air from low pressure chillers? |
Purge pump |
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ln an absorptionchiller, what drives the refrigeration process? |
Heat Energy |
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The type of energy used to power a typical absorption refrigeration machine is: |
Natural Gas |
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What is the primary concern with phase loss/unbalance in large motors? |
Overheating |
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In Addition to the building heat load, what else must the cooling tower remove from a system? |
Heat of compression |
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In which evaporator, the refrigerant is in the tubes and water floods the shell. |
DX |
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Two technicians observe that a water-cooled chiller has a very high condenser approach temp. The system has slightly high super-heat and 12 degrees F sub-cool. Technician A says that the condenser tubes are likely fouled with mineral. Technician B says that the system is likely low on refrigerant. Which technician is correct? a. Tech A b. Tech B c. Both Techs d. Neither Tech |
A |
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What is the typical design water temp that a cooling tower should supply to a chiller? |
85° |
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You arrive at a job and find the condenser entering water temp is 90 F". You measure the outdoor air and record 108 F' with a wet bulb temp of 85 F. What is wrong? |
Nothing |
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Why must a cooling tower have a blow-down valve |
Dump minerals |
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Most low-pressurechillers have rupture disks/relief valves set at: |
15° |
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What is the refrigerant used in large commercial absorption chillers? |
Water |
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What substance is used to lubricate the seals in a water pump? |
Water |
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A starter reconfigures the motor windings to be wired in series between each leg of power at startup |
Wye Delta |
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Surge is caused by: |
Refrigerant flows backwards |
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An oil analysis is done on centrifugal chillers annually to detect what? |
Moisture, Acid and Metals |
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When charging a chiller using sub cooling, you should stop charging once you have a subcooled reading of? |
10° to 12° |
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A 100 ton chiller requires how many GPM of condenser water flow? |
300 gallons per minute |
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Before starting any chiller, the various heaters (crankcase, oil separator, oil sump, and casting) must have been energized for _ hours? |
24 hours |
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Prior to starting the compressor. Two technicians observe that a chiller has high sub cooling and high evaporator approach. Technician A says that the chiller is low on charge. Technician B says that the metering device is the problem. Which technician is correct? |
B |
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Condenser approach is measured as the difference between leaving water temp and ? |
Saturation temp of refrigerant |
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What kind of brushes should be used to clean flooded condenser water tubes at least once per year? |
Non metallic |
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What must absolutely never be allowed to happen in a chiller with a flooded evaporator? |
Freeze up |
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Convert 10 Psi to feet of head. |
20° |
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If a chiller with two-pass vessels is making 6 degrees delta across the evaporator, what should the condenser temperature rise be? |
6° |
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A partial liquid line restriction cause’shigh head pressure.
True or False? |
True
FOULED TUBES (explain) |
