Home > Flashcards > Print Preview
The flashcards below were created by user
on FreezingBlue Flashcards. What would you like to do?
What is the purpose of Type II Certification?
To certify technicians maintaining, servicing, repairing or disposing of high pressure or very high pressure appliances
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
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
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%
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
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
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
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
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
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
What are the recovery requirements?
Refrigerant recovery/recycling equipment manufactured after 11/15/93 must be certified by the EPA
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
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
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
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
What was the most common refrigerant used in residential split air conditioning systems?
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
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
What should the vacuum pump be capable of pulling?
For a vapor compression system, it should pull 500 microns of vacuum
What could happen if a hermetic compressor were energized under s deep vacuum?
The motor winding could be damaged
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
What causes higher discharge pressure?
Non-condensables, mainly consisting of air
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
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