EPA III Flash Flashcards
When leak testing a low pressure refrigeration system with nitrogen, what is the maximum test pressure?
10 psig
Continuous excessive moisture collection in the purge unit of a low pressure refrigeration system could indicate what condition?
The condenser or chiller barrel tubes are leaking
Leak testing a low pressure refrigeration system with nitrogen in excess of 10 psig could cause which of the following to fail?
Rupture disc, set at 15 psig
What is meant by the term “high efficiency purge unit?”
Purge units which discharge a low percentage of refrigerant with the air which they remove
Where is the lowest access point on a low pressure centrifugal AC appliance?
Evaporator charging valve
After system servicing, why is refrigerant vapor re-introduced to the refrigeration system before refrigerant liquid?
Liquid charged into a deep vacuum will boil and may lower temps enough to freeze water in the tubes
When using recovery and recycling equipment manufactured AFTER 11/15/93, techs must evacuate low-pressure appliances to the following level before disposing of the appliance:
25mm Hg absolute
Appliances need not be evacuated all the way to the prescribed level when:
Leaks in the appliance make evacuation to the prescribed level unattainable
When using recovery and recycling equipment manufactured BEFORE 11/15/93, techs must evacuate low-pressure appliances to the following level before making a major repair:
25 inches Hg vacuum
What repairs are ALWAYS considered “major” under EPA?
Replacement of compressor, condenser, evaporator, or auxillary heat transer coils
Under EPA’s regulations, which of the following methods can be used to pressurize a CFC-11 or HCFC-123 system for the purpose of opening the system for a non-major repair?
Warming the refrigerant (controlled hot water, thermal wraps)
When recharging a refrigeation system with CFC-11, what vapor pressure is necessary in the shells before charging with liquid?
16.9” Hg vacuum, increase temp over 36 degrees F
During vapor removal from a low pressure refrigeration system what systems should be on?
The system water pumps, the recovery compressor, and the recovery condenser water should all be on
According to ASHRAE Guideline 3-1996, if the pressure in a system rises from 1mm Hg to a level above ________ during a standing vacuum test, the system should be check for leaks
2.5mm Hg absolute
CFC-11 or HCFC-123 system refrigerant removal starts with:
Liquid Removal
A rupture disc on a recovery vessel for low pressure refrigerants relieves at:
15 psig
What is the primary water source for a recovery unit condensing coil?
Local municipal water supply
When removing oil from a low pressure system, the temp should be 130 degrees F because:
Less refrigerant will be contained in the oil at the higher temp
Identify the pressure corresponding to 32 degrees F for HCFC-123:
20 inches of Hg vacuum
When evacuating a system, the use of a large vacuum pump could:
cause trapped water to freeze
The PRIMARY purpose of a purge unit on a CFC-11 chiller is to:
Remove non-condensibles from the system
Where does refrigerant go after it leaves the purge unit of a low pressure centrifugal system?
The evaporator
Refrigerant is added to a centrifugal machine through the:
Evaporator charging valve
Which of the following safety precautions should be adhered to for low pressure systems?
Do not syphon refrig by mouth, avoid spilling refrig on skin, use gloves and goggles
ASHRAE Standard 15-1994 requires that each machinery room shall activate an alarm and mechanical ventilation before refrigerant concentrations exceed:
The TLV-TWA (threshold Limit Value - Time Weighted Average)
What can charging liquid into a low-pressure system under 29” Hg cause?
System water freezing.
For low-pressure units which will be idle for some time, what should be done to prevent air from entering the system?
Maintain a pressure slightly above atmospheric.
If a high capacity vacuum pump causes trapped water in the system to freeze, you must increase the system pressure to allow the ice to melt. What is the only substance that can be used to increase the pressure?
Dry Nitrogen.
What is the most common B1 rated refrigerant in Type III systems?
HCFC-123.
