| A | B |
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| Low pressure chillers are typically charged with ________ through the evaporator charging valve. | liquid |
| To prevent freeze up, the intial refrigerant charge into an evacuated system should be in _________ only. | vapor state |
| Adding liquid refrigerant should be avoided until the gauge pressure when checked against a pressure temperature chart for the refrigerant in use indicates a temperature __________. | above freezing, typically 36 degrees farenheit |
| Liquid refrigerant that is into a chiller that is under a deep vacuum will ___________. | drop to an extremely low temperature |
| __________ are used in low-pressure chillers to relieve pressure. | Rupture discs |
| The rupture disc is connected at the evaporator and is typically set to open at ______. | 15 psig |
| The rupture disc is piped to the _______ for venting. | outdoors |
| Since water is often present in the chilled water pump and water tubing, the _________ should be running during a _________. | circulating pump, recovery |
| Charging refrigerant liquid inot a refrigeration system under ________ vacuum can cause the system water to freeze. | 29 in. Hg. |
| When __________ a refrigeration systemw ith CFC-11, ________ vacuum is necessary in the shells before charging with liquid. | recharging, 16.9 in. Hg. |
| The lowest access point on a low pressure centrifugal air conditioner is the _______. | evaporating charging valve |
| If a system is not fully evacuated, _________. | compressor head pressure can rise |
| The system pressure in idle low pressure equipment should be maintained slightly above _______to prevent air accumulation. | atmospheric |
| The refrigerant in low pressure equipment is typically at pressures _________. | below atmospheric |
| Air leakage and moisture entering the system are common problems due to the many ________. | gaskets and fittings |
| To minimize the effects of contamination, ________ are almost universally used. | purge cycles |
| Purging is accomplished with a purge system made up of a __________. | compressor, oil separator and purge drum |
| The inlet of the purge compressor is typically connected to the __________. | top of the condenser |
| During a purge cycle, non-condensables from within the chiller are _________. | drawn off and sent to the purge drum |
| At the purge drum the non-condensables and refrigerant vapor are separated using _______. | distillation and the refrigerant vapor is returned to the system |
| A hydrostatic test is used to check for _________. | tubing leaks within a chiller |
| To prevent moisture from being drawn into the refrigerant tubing, the water circuits of the evaporator and condenser should be _______. | drained |
| The _____ type compressor uses a motor located outside the compressor body. | "open" |
| The external drives of these "open" compressors can include ___________, while others are driven directly by the ________. | pulleys and drive belts, motor (direct drive) |
| A disadvantage of the open type is that there must be a seal where _________. | the shaft enters the compressor body |
| Low pressure equipment with a partial charge can be checked by _________. | increasing the refrigerant pressure using an external heat source or running hot water in the chiller tubes |
| When leak checking with dry nitrogen, the pressure must not exceed _______. | 10 PSIG (Excessive pressure could cause a rupture disc failure) |
| Low pressure equipment without a charge can be leak checked using ________. | a "time to rise" test |
| In the "time to rise" test, the equipment is pulled down to ____________. | a deep vacuum, usually 1-mm hg. |
| The system is then valved off and a check is made of the ________. | stability of the vacuum |
| At the end of this check, the vacuum reading should not increase to more than _______. | 2.5-mm hg. (Ashrae Standard 3-1990) |
| The need for purging can be reduced by ________. | leak checking and repairing any leaks on a regular schedule |
| When leak checking a low-pressure system for leaks between the refrigerant circuits and the water circuits, __________. | the chiller barrel can be emptied of all water and a leak check can be made at the drain valve with the water off |
| Effective __________, any annualized leak rate of _______ or more in commercial refrigeration or industrial process equipment with 50 pounds of charge or more must be repaired. | June 14, 1993, 35% |
| For appliances other than industrial process equipment and commercial refrigeration, an annual leak rate of ________ must be repaired. | 15% or more |
| ________or ______ system refrigerant removal starts with liquid removal. | CFC-11, HCFC-123 |
| One shortcoming with liquid recovery is _______. | that some vapor remains in the system and cannot be removed |
| A vapor recovery must be used to remove any | remaining refrigerant vapor |
| When the removal of the oil from a low pressur system is required, the oil should be heated to ________. | 130 F because less refrigerant will be contained in the oil at the higher temperature |
| Vapor recovery condensers can be either _______. | air-cooled or water-cooled |
| When using the ________ method to recover refrigerant from a low pressure chiller the recovery unit's high-pressure cut-out should be set for _____.' | push-pull, 10 psig |
| During vapor removal from the refrigerations system,the system water pumps, the recovery compressor, and the recovery condenser water should _____. | all be on |
| Once the machine cuts off on low pressure (or manually) the recovery process is not _______. | necessarily complete |
| To pressurize a system prior to a minor repair a technician can increase the refrigerant pressure __________. | using an external heat source or running hot water in the chiller tubes |
| Technicians must evacuate ______ components to the lowest level attainable without _________. | LEAKING,substantially contaminating the refrigerant(This level cannot exceed 0 psig) |
| __________ and _________ machines are not required to recover more than one type of refrigerant. | Recovery and recycling |
| If the vacuum pump has a high capacity, the reduction in the pressure on the system can cause | any moisture in the system to freeze |
| The frozen moisture can often be removed by _________. | increasing the pressure to allow the ice to melt |
| __________ specifies the requirements and use of refrigerant sensors in equipment machine rooms. | ASHRAE Standard 15 |
| ___________ requires equipment rooms to have refrigerant sensors for _________. | ASHRAE Standard 15, ALL refrigerant safety groups |
| According to __________, each machinery room shall ____________. | ASHRAE Standard 15, activate an alarm and mechanical ventilation system before refrigerant concentrations exceed the TLV-TWA (Threshold Limit Value-Time Weighted Average) |
| When using low-pressure refrigerants, avoid ________. | siphoning refrigerant by mouth |
| The higher toxicity refrigerants are the ________, and the mostly commonly used in this group is _______. | "B1", HCFC-123 |
| If more than one relief valve is used, __________. | they must not be installed in series |
