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49 Cards in this Set
- Front
- Back
How can ice be removed from a sight glass?
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Cleaned with an alcohol spray.
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How high should you pressurize an idle low pressure chiller to prevent air accumulation?
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Slightly above atmospheric pressure.
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What effect does air in a chiller have on head pressure?
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Raises head pressure.
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What system failures require taking and oil sample?
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A leak or major component failure (compressor burnout).
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Why must water be circulated through a chiller during refrigerant recovery?
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To prevent freeze-up of the water as pressure is reduced on the refrigerant.
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What is the lowest access valve on a low pressure chiller?
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The evaporator charging valve.
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Where is a centrifugal chiller's rupture disk attached?
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At the evaporator.
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What is the typical pressure setting for a low pressure chiller's rupture disk?
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15 PSIG.
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Where is the outlet of a rupture disk discharged?
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Outdoor for venting.
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How is a chiller typically charged?
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Liquid through the evaporator charging valve.
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What minimum saturation temperature needs to be achieved before liquid is charged into a chiller?
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Above freezing, typically 36 deg. F.
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To prevent freezing of water when charging a chiller, what pressure should be reached with vapor before using liquid CFC-11?
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16.9 inches of Hg.
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What could result from liquid refrigerant being charged into a chiller that is holding a 29 inch Hg. vacuum?
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Can cause system water to freeze.
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What function is served by a purge unit on a chiller?
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Minimize the effects of contamination. To remove non-condensables.
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What is the most likely cause of air leaks into a chiller refrigerant circuit?
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Gaskets and fittings.
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How is a purge unit connected on a low pressure chiller?
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The inlet of the purge unit is typically connected to the top of the condenser.
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Where is the suction of a purge unit connected?
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The inlet of the purge unit is typically connected to the top of the condenser.
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What is a high efficiency purge unit?
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It removes non-condensables that contain a low percentage of refrigerant. This adds to the value of the purge drum in refrigerant containment.
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Shaft seals on an open type compressor are susceptible to what failures?
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Refrigerant leaks.
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Purge units work best when they are not needed. How can purge unit operating time be reduced?
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By regular leak checking and repairing any leaks on a regular schedule.
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What is the maximum pressure that can be used when leak checking a low pressure chiller?
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10 PSIG on low pressure equipment that utilizes a rupture disk.
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What is the preferred method of leak checking a charged low pressure chiller?
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By increasing the refrigerant pressure using an external heat source or running hot water through the chiller tubes not to exceed 10 PSIG.
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Where should you check for leaks between a chiller refrigerant tube and the water box?
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The chiller barrel can be emptied of all water and a leak check can be made at the drain valve with the water off. If the tubes themselves require a leak check, the check can be made with a hydrostatic tube test kit.
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What is a hydrostatic tube test kit used for?
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To check for leaks in a chiller tubes.
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What leak rate is permissible on industrial and process refrigeration?
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Effective 6/14/93, any annualized leak rate of 35% or more on equipment with 50 lbs. of charge or more must be repaired. Less than 35% is permissible.
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What leak rate is permissible on equipment other than industrial and process equipment?
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For appliances with 50 lbs. of charge or more an annual leak rate of 15% or more must be repaired. Less than 15% leak rate is permissible.
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According to ASHRAE 3-1990, what rise is permitted in vacuum level during a standing vacuum test?
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Starting at 1mm of Hg., after 12 hours the vacuum reading should not increase to more than 2.5 mm of Hg.
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List two steps to reduce the run time of a purge unit.
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Regular leak checks and repair any leaks.
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Why should the water side of the evaporator and condenser be drained before recovering refrigerant from a chiller suspected of having tube leaks?
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To prevent moisture from being drawn into the refrigerant circuit.
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If a purge unit is operating excessively, what problem can you expect to find?
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Leaks.
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What condition would cause continuous excessive moisture collection in the purge unit of a low pressure refrigeration system?
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Leaks between the refrigerant circuit and the water circuit.
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Why should oil be warmed prior to removal from a low pressure chiller?
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To vaporize any liquid refrigerant that might be trapped in the oil.
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After liquid recovery, what must be done with the vapor still in the system?
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Vapor recovery must be performed.
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Is recovery of refrigerant from a low pressure appliance typically started with liquid or vapor?
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Start with liquid removal.
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Where is the connection made for the water supply used on a water cooled recovery unit?
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Local water supply.
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What should be the maximum pressure on the discharge of a recovery machine for low pressure systems?
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10 PSIG, because the rupture disk is set to open at 15 PSIG.
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What should be done with the water pumps during a recovery form a low pressure chiller?
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Turned On
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What is EPA's definition of a "major repair"?
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Any repair that involves the removal of the compressor, evaporator, condenser, or any auxiliary heat exchange coil.
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What recovery vacuum must be met on a low pressure appliance using a machine built in 1992?
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25 inches of Hg.
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Why should you wait a few minutes after reaching the required recovery vacuum on an appliance to see if pressure rises?
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To see if refrigerant is still trapped in the system.
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Under what circumstances may the recovery from an appliance be stopped without reaching the prescribed level?
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If the recovery would contaminate the refrigerant being recovered (this level cannot exceed 0 PSIG.)
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Is it a requirement that recycling and recovery equipment be capable of handling more than one refrigerant?
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No
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Is it permissible to warm the refrigerant under EPA's regulations to pressurize a low pressure system to do a non-major repair?
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Yes
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What final vacuum level is required for recovering refrigerant from a low pressure system if the technician is using recovery equipment manufactured BEFORE November 15, 1993? After November 15, 1993?
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25 inches of Hg, 25 mm of Hg. Absolute (equal to about 29 inches of Hg.)
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Are multiple relief valves connected in series or parallel?
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Parallel
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ASHRAE Standard 15 covers refrigerant level monitoring for what refrigerants?
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All
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According to ASHRAE Standard 15, what is the standard for refrigerant concentration for a machine room that must not be exceeded without activating an alarm and starting ventilation in the machine room?
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May not exceed the TLV-TWA. (Threshold limit value-Time weighted average.)
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List four safety procedures that should be followed when working with liquid low pressure refrigerant.
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1. Use refrigerant sensors in equipment room. 2. Avoid siphoning refrigerant by mouth. 3. Wear butyl-lined gloves. 4. Wear safety glasses.
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What is the toxicity and flammability rating of HCFC-123 per ASHRAE Standard 34?
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B1.
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