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What is the purpose of Type II Certification?
To certify technicians maintaining, servicing, repairing or disposing of high pressure or very high pressure appliances
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What are the requirements for leak detection?
- After installation of any type of system, the unit should first be pressurized with nitrogen (an inert gas) and leak checked
- Use electronic or ultrasonic leak detector, the soap bubbles to pinpoint any leaks
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What visual indication would alert the technician that there may be a leak?
- Traces of oil
- Excessive superheat, caused by low refrigerant charge
- Units using an open compressors may leak from the rotating shaft seal
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What are the requirements for leak repairs?
- EPA regulations require that all comfort cooling aplliances containing more that 50 pounds of refrigerant MUST be repaired when the leak rate exceeds 15%
- Regulations require that all Commmercial and Industrial Process Regrigeration containing more than 50 pounds of refrigerant MUST be repaired when the leak rate exceeds 35%
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Describe the recovery techniques for Type II.
- Appropriate recovery equipmet that has been certified by UL or ETL to meet or exceed ARI standards
- Recovered refrigerants may contain acids, moisture, and oil therefore ensure to check and change both the oil and filter on a recycling machine
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What happens when using equipment with a hermetic compressor?
- They have the potential to overheat when drawing a deep vacuum because the unit relieson the flow of refrigerant through the compressor for cooling
- Ensure you check the service valve positions, the oil level of the recovery unit, and evacuate and recover any refrigerant from the unit's receiver
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What should the technician do when working with multiple refrigerants?
- Must purge the recover/recycle equipment by recovering as much of the first refrigerant as possible, change the filter, and evacuate
- Only exception is when working with R-134a when a special set of hoses, gauges, vacuum pump, recovery recycling machine, and oil containers to be used with R-134a only
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What is the difference in recovering vapor and liquid?
- Vapor phase will minimize the loss of oil, recovering as much as possible in the liquid phas can reduce recovery time
- Technicians may choose to speed up the process by packing the cylinder in ice and/or applying heat to the appliance
- After recovery of liquid refrigerant, any remaining vapor is condensed by the recovery system
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What should you do when servicing a unit that has a receiver/storage tank?
- Refrigerant should be placed in the receiver, should be removed from the condenser outlet if the condenser is below the receiver
- If the air cooled condenser is above the evaporator, recovery should begin from the liquid line entering the evaporator
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What may be accomplished after recovery?
- Refrigerant may be returned to the appliance from which it was removed without being recycled or reclaimed, unless the appliance an motor vehicle air conditioner like appliance
- Technicians should always evacuate an empty recovery cylinder before transferring to the cylinder
- Quick couplers, self sealing hoses, or hand valves should be used to minimize refrigerant release when hoses are connected or disconnected
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What are the recovery requirements?
Refrigerant recovery/recycling equipment manufactured after 11/15/93 must be certified by the EPA
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What are the required recovery levels for Type II appliances? (in inches of mercury, before and after 11/15/93)
- HCFC <200 lbs of refrigerant 0/0
- HCFC >200 lbs of refrigerant 4/10
- Other appliances<200 lbs of refrigerant 4/10
- Other appliances >200 lbs of refrigerant 4/15
- Very high pressure appliances 0/0
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What should the technician do after reaching the desired vacuum?
- Wait a few minutes to see if the system pressure rises, indicating that there is still refrigerant in liquid form or in the oil
- Appliances can be evacuated to 0 psig if leaks make evacuation to the prescribed level unattainable
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How does the technition recover the refrigerant?
- Must isolate a parallel compressor system
- Failure to isolate a parallel compressor system will cause an open equalization connection that will prevent refrigerant recovery
- System dependant recovery equipment cannot be used on appliances containing more than 15 pounds of refrigerant
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Under EPA regulations, what does major repair entail?
Any maintenance, service or repair involving the removal of any or all of the following components: compressor, condenser, evaporator, or an auxiliary heat exchanger coil
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What was the most common refrigerant used in residential split air conditioning systems?
R-22
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What is the purpose of filter driers?
- Remove moisture from the refrigerant in a system
- Some systems are equipped with a moisture indicating sight glass.
- Filter drier should be replaced anytime a system is opened for servicing
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What is a crankcase hearter used for?
- Prevent refrigerant from migrating to the oil during periods of low ambient temperature
- Refrigerant in the oil will cause oil foaming in the compressor at start up
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What should the vacuum pump be capable of pulling?
For a vapor compression system, it should pull 500 microns of vacuum
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What could happen if a hermetic compressor were energized under s deep vacuum?
The motor winding could be damaged
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What could happen with a large vacuum pump?
- It could cause, trapped water to freeze
- During evacuation of systems with large amounts of water, it may be necessary to increase pressure by introducing nitrogen to counteract freezing
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What causes higher discharge pressure?
Non-condensables, mainly consisting of air
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What should you do when there is a risk of freezing?
- Liquid charging an R-12 system should begin with vapor from a vacuum level to a pressure of 33 psig
- Followed by a liquid charge through the liquid line ervice valve
- This is also the proper method to charge a system that contains a large quantity of refrigerant
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What are the additional safety requirements?
- ASHRAE standard 15 requires a sensor that will sound an alarm and aoutmatically start a vent system where refrigerant will concentrate
- Refrigerants CFC-12, CFC-11, and HFC-134a are categorized as A-1
- All systems must be protected by a pressure relief valve not in series
- NEVER energize a reciprocating compressor if the discharge service valve is closed
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