Recall from our module on Refrigerant Oils that oils can react with water to create toxic and corrosive acids. This will cause major system failures. So we do not want water or water vapor in the system.
Dehydration is the process of removing water and water vapor from the system. We dehydrate the system by evacuating it.
The recommended method to dehydrate a system is to evacuate it. Evacuation is when we remove all water vapor and air from the system.
A system is considered dehydrated when you have reached and held a vacuum of 500 microns or less.
If the system contains a hermetic compressor, you need to make sure it is not operating when you pull a dehydration vacuum. If the hermetic compressor is operating, it will prevent you from pulling a deep vacuum.
So basically, in addition to removing all the water vapor from a system, evacuation includes removing all the air from the system as well.
So to reiterate, evacuation is the best method for dehydrating a system. We also need to evacuate a system before any major system repairs.
To remove all the air and water vapor from the system, we need to use a vacuum pump to pull a vacuum on our system.
To pull a vacuum, we need to make sure that the vacuum pump is capable of pulling a deep vacuum. We define a deep vacuum to be 500 microns.
Vacuum lines or hoses need to be equal to or larger than the pump intake connection. If the mouth of the hose is smaller, you would not be able to pull a vacuum.
Over-evacuation of a system does not occur. Recall that the purpose of evacuation is to remove all air and water from the system.
You cannot remove too much air and water from the system because you want all of it to be gone. If you evacuate past the point that is necessary, this will not damage refrigeration line sets. This is because they are made of metal such as copper, aluminum, or steel.
You have reached dehydration when the vacuum indicator shows you have reached and held a vacuum of 500 microns or less.
Dehydrating time is the time it takes to remove all water and water vapor from a system. Recall that dehydrating is done by evacuating a system, which involves removing air and water from the system.
We generally want to minimize the amount of time spend dehydrating a system. The longer we spend dehydrating, the larger the risk of any component failing in the system. Your time as a technician is also valuable.
That being said, we need to make sure we are taking safe measures to decrease our dehydration time. Safety is always number one.
The larger the equipment, the longer it will take to dehydrate it. This is simply because there is more work to do. Imagine mowing a lawn. The bigger the lawn, the more time it takes to get the job done.
The ambient temperature is the temperature of the system. The colder it is or the lower the ambient temperature, the more time it’s going to take to dehydrate.
That’s why we want to heat up the system to decrease the dehydration time. The higher the temperature, the less time it will take to dehydrate. We can use a heat blanket to heat the system safely.
Recall that we never use a flame to heat up the system. We are working with possibly flammable materials that operate on high pressure. Using an open flame can lead to explosions.
The more moisture there is in the system, the longer it will take the dehydrate the system. Going back to the lawn mowing scenario, the mount of moisture would be like the amount of overgrown grass in your lawn. The more grass you have, the longer it will take to mow.
And lastly, the vacuum capacity is the rate at which your vacuum can pull out moisture and air. The smaller your vacuum capacity, the longer it will take to dehydrate the system. The smaller your lawn mower, the longer it takes to mow the lawn.
The longer the suction line, the longer it will take a dehydrate a system. That’s why we want to keep the suction line as short as possible.
In this module, we defined the term dehydration and discussed the factors affecting dehydration time.
What are the typical uses of the center port of gauge set?
Used during evacuation, charging and recovery procedures.
What color are the gauges on a manifold gauge set?
Low pressure is blue, High pressure is red.
What are the typical ranges of pressure measurements used on the gauges of a manifold gauge set?
High side is 0 to 500 PSIG; Low side is 0 to 350 PSIG and 0 to 30 in. Hg below atmospheric pressure.
Is the refrigerant leaving a condenser at a high or low pressure? Is it a liquid or a gas?
Is the refrigerant entering the expansion valve (variable metering device) a liquid or gas?
Is the pressure of the refrigerant entering the compressor high or low?
Where in a refrigerant circuit does a liquid boil to absorb heat?
The refrigerant in the suction line is a gas that has been heated above its saturation. What is this condition called?
What can cause liquid refrigerant to migrate to a compressor crankcase?
If the compressor is located in the coldest location in the circuit.
List two conditions that can quickly damage a compressor that is starting to run?
Operating while in a deep vacuum or when the service valves are closed.
What system failures require taking an oil sample?
A compressor burnout or if the unit has had a leak.
Is flushing with refrigerant an acceptable tube cleaning method?
In addition to preventing and repairing leaks, what else should a technician do to conserve refrigerant?
Recover and recycle used refrigerants.
What factors affect the speed of an evacuation?
Pump size, hose length, hose diameter, size of system to be evacuated, ambient temperature, suction line size, and the amount of moisture in the system.
How should gauge set hoses be sized for use in evacuating a system?
Use the shortest length and the largest diameter possible for the quickest evacuation. At least as large as the vacuum pump inlet.
When evacuating, what is the benefit of using short hoses with large diameters?
Reduces emissions, pressure drop and evacuation time.
which connection determines the preferred size of hoses used with a vacuum pump?
As the capacity and suction hose size increase, what happens to the time needed for an evacuation?
What purpose is served by heating a system during dehydration?
To speed up moisture removal.
Does a thorough evacuation remove moisture from a system?
What can happen to oil in the compressor if the moisture is left in an operating system?
The oil will form hydrofluoric and hydrochloric acids which will corrode the internal parts of the system.
What is the result of over-evacuating a system?
How can a system be leak checked using a low pressure gauge?
Vacuum reading will rise when vacuum pump is turned off.
How close should the vacuum gauge be connected to the vacuum pump during evacuation?
When measuring the vacuum of a system being evacuated, the system must be isolated. What must be done to the vacuum pump?
Turn it off and valve it off.
3 atoms of oxygen. It blocks much of the harmful ultraviolet radiation (uv-b) emitted from the sun and it keeps our earth's temperature stable.
How much ozone can a chlorine atom destroy in the stratosphere?
One atom can destroy 100,000 ozone molecules.
What is Ozone Depletion Potential (ODP)?
The ability of any chemical to deplete the ozone layer.
Which refrigerants are CFC's?
Which chemical in the CFC refrigerants does the most damage to the ozone layer?
Hydrochlorofluorocarbons.
Which refrigerants are HCFC's?
Which is more harmful to the ozone layer, a CFC or an HCFC?
What is it about CFC's that make them more harmful to the stratosphere?
Chemical strength, they will not breakdown in the lower atmosphere.
A fluorocarbon that contains no chlorine.
Which refrigerants are HFC's?
What is the ODP of the HFC refrigerant?
Which refrigerants contain chlorine?
Which refrigerants have high ODP?
Which refrigerants have low ODP?
What is an azeotrope refrigerant?
A mixture of two or more compounds where the mixture behaves like a single chemical.
Is one of the components of R-500 a CFC?
Does stratospheric ozone help or hurt the work of the earth's protective shield?
What chemical in the stratosphere tells us ozone depletion is occurring?
How do we know the chlorine in the stratosphere is coming from CFC's?
The increase in chlorine and fluorine present in the stratosphere, matches the increase in emissions of CFC's.
How do we know CFC's get to the stratosphere?
From high altitude air sampling measurements.
What role does the ozone layer play in protecting the earth?
It blocks much of the harmful ultraviolet radiation (uv-b).
What are the effects on health from increased ultraviolet radiation?
Skin cancer, cataracts, human immunity is reduced.
What are the effects on the environment?
Timber growth is reduced, crop yields lowered, marine life and the food chain are impaired.
Is ozone depletion a problem for the United States only or a global problem?
What is the Montreal Protocol?
A treaty that called for the reduction of production of CFC's.
The Montreal Protocol calls for the regulation of what chemicals?
Ozone depleting compounds, CFC's, HCFC's, and Halons.
On what date was the production and importation of all CFC's phased out?
In the U.S., after December 31, 1995.
Where will we get replacements?
Through recovery of existing refrigerants.
What steps are called for by the Clean Air Act?
Taxes on production and use, standards set for the recovery of refrigerants.
What is prohibited by the Clean Air Act?
Do state and local laws have priority over federal law? Can they be less strict?
No. Cities or states can create their own laws but they must be at least as strict as federal laws.
To prevent damage to the ozone layer, the U.S. is making laws to capture the CFC's now in use. What else does the new law do to restrict the release of CFC's?
Allows states and municipalities to create their own laws to prevent and monitor the release of CFC and HCFC materials into the atmosphere.
By recovering refrigerants, we ensure adequate supplies and prevent venting. What else does the recovery of refrigerants accomplish?
Prevents stratospheric ozone depletion.
The Clean Air Act phases out CFC/HCFC production and prohibits venting. What else does it require?
Standards to be set for recovery of all refrigerants prior to appliance service and disposal.
Falsifying or failing to keep required records, failing to reach required evacuation levels and knowingly releasing CFC or HCFC refrigerants, are a violations of the Clean Air Act. What activity with a substitute refrigerant is also a violation?
Knowingly venting CFC's, HCFC's and their substitutes.
Which refrigerants must be recovered prior to opening a system?
All refrigerants as of 11-15-1995.
What releases of a CFC and HCFC are violations of the Clean Air Act?
Any knowingly vented refrigerants.
On what date did it become illegal to vent CFC and HCFC refrigerants?
Which appliances are covered by Section 608?
Any device which contains and uses a class 1 or class 2 substance as a refrigerant and is used for household or commercial purposes.
What is the primary reason the EPA requires a service aperture or process stub on all appliances?
For adding or removing refrigerant from the appliance.
Who sets the regulations for recovery machines?
What is a "self-contained" recovery machines?
A recovery machine that has its own compressor to pump refrigerant out of the system.
Is HCFC-123 a "low or "high" pressure refrigerant?
Is CFC-12 a "low" or "high" pressure refrigerant?
What is the smallest container in which refrigerants may be sold to a Section 608 certified technicians.
What must you do to the refrigerant in an appliance before disposing of the appliance?
Recover refrigerant or verify that the refrigerant was previously recovered.
Who is responsible for removing the refrigerant from household refrigerators prior to disposal?
The final person in the disposal chain. (Scrap metal recyclers, landfill owner, etc)
What is the penalty for violation of the Clean Air Act?
Fines up to $27,500 per violation per day and possible loss of technician certification.
How much is the bounty for information leading to a conviction?
What ca happen if a technician cannot demonstrate an ability to use recovery or recycling equipment?
May result in revocation of the technician's certification.
What is the name of the process that removes refrigerant from a system and stores it without testing or processing?
What is the name for the process that removes moisture and acids from refrigerant but does not test the refrigerant?
What is the name for the process that removes moisture and acids from refrigerant and also chemically tests the refrigerant?
What must be done with reclaimed refrigerant before it can be legally resold?
Chemically tested to ARI Standard 700, the purity level of factory new refrigerant.
What is the preferred instrument for detecting small leaks?
Electronic leak detector and Ultrasonic detector.
What is an inert gas typically used in leak detection?
What is typically indicated by a dehydrated system failing to hold a vacuum?
What should be done when recovering the refrigerant form a system where the refrigerant has been improperly mixed?
Recover into a separate container?
Can mixed refrigerants be reclaimed?
What precautions should be taken when recovering refrigerant from systems with multiple service valves?
Insure that liquid is not trapped between service valves.
What is the effect of low ambient temperature on the time required to complete a recovery of refrigerant?
Technicians must explain to customers that recovery is necessary and it is required by law. What else should the technician tell the customer?
That all service personnel are duty bound to follow the law and protect the environment.
What is different about any leaks in systems charged with a blended refrigerant?
Because they are blended, the ingredients will leak at different rates.
What is "temperature glide"?
A family of lines depicting pressure versus temperature curve.
A blend of three different refrigerants.
How should systems using blended refrigerants be charged?
In liquid form into the high side of the system.
Is there a "drop-in" refrigerant for CFC-12?
How do you leak check an HFC-134a system with a partial charge (no HFC-134a detector available)?
Recover the remaining 134a and then pressurize the system with nitrogen and a trace charge of R-22 so you can use an HCFC electronic leak detector.
What is the preferred oil to be used with HFC-134a?
Can ester based oils be mixed with other oils?
What does "hygroscopic" mean?
Oil that absorbs moisture easily.
What lubricant is recommended for use with a ternary blend?
Depends on the blend: For HCFC's-Alkylbenze, For HFC's-Ployolester.
Safety glasses and butyl-lined gloves should be worn for what procedures?
When operating recovery or recycling devices and when handling and refilling refrigerant cylinders.
What safety component must be used whenever dry nitrogen is used to pressurize a system?
Safety rules for technicians such as: no open flame or hot steam near a refrigerant, never cutting or brazing a charged refrigerant line, and never using oxygen to purge or pressurize lines, are all important. Which one should a technician follow?
What is a Material Safety Data Sheet?
A sheet the states the safety ratings and precautions to be taken for use and handling of chemicals.
What safety classification within the ASHRAE standard is the most safe?
What is caused by tie inhaling of refrigerant vapors?
Heart irregularities or Asphyxia.
What is the major causes of death involving refrigerants?
What breathing problem can be caused by CFC-12?
How can ice be removed from a sight glass?
What must be done with a badly corroded relief valve?
Where can you find the allowable test pressure on a system?
Can oxygen be used to check for leaks? If not, why not?
No. Oxygen in the presence of oil under high pressure can be explosive.
What is the likely result of heating a recovery cylinder with an open flame?
Refrigerant will decompose into a toxic material, venting of refrigerant int the atmosphere or the tank may explode.
What is the primary purpose of a disposable cylinder?
For virgin refrigerant from the manufacturer.
To what internal pressure should a disposable cylinder be reduced to for disposal?
Reduced to at least 0 PSIG.
Should you ever use a disposable cylinder for refrigerant recovery?
To dispose of a cylinder you should be sure all refrigerant is recovered and the cylinder is no longer usable. What else should you do?
Puncture the container before disposal.
For safety, refrigerant chlinders should not be rusted or damaged and always properly color coded. What additional step should also be taken with these cylinders?
Properly secured at all times.
What is the proper color code for recovery cylinders?
What is the maximum percent by weight that a cylinder may be filled?
What can happen if a cylinder is overfilled?
Hydrostatic pressure could cause the cylinder to explode.
List three methods for measuring the fill level of a recovery cylinder.
Floats, thermistor type sensors, and weighing scales.
Wow often must reusable cylinders be hydrostatically tested?
Why must only refillable cylinders be used for transport?
Federal code of regulations title 49 (parts 100-177) states this.
What must be affixed to a refrigerant cylinder prior to its shipment to a reclaimer?
What is the purpose of a DOT classification tag?
For transportation purposes.
What is the correct shipping position for a refrigerant cylinder?
In a vertical or upright position with their valves at the top.
What is the EPA definition of a small appliance?
Appliances typically charged at the factory with five pounds or less of refrigerant. Refrigerators and freezers designed for home use, room air conditioners, including window and PTAC units, package heat pumps, dehumidifiers, under the counter ice makers, vending machines and drinking water coolers.
Does the EPA require the repair of leaks on small appliances?
Repair of leaks on small appliances is not required, but leaks should be repaired whenever possible.
What EPA certification type must technicians have to service any appliance that EPA calls a "small appliance?"
What service aperture may be used on small appliance?
Access tubes or process tubes.
What is the name for a fitting, used to connect a recovery device to an appliance, which can close to prevent loss of refrigerant form hoses?
Low-loss fitting. (shut-off valve)
What is the primary purpose for using hand valves or self-sealing hoses when using a gauge set?
To prevent loss of refrigerant.
Which refrigerants must be recovered under Section 608 of the EPA regulations?
CFC, HCFC and HFC refrigerant.
Is there a "drop-in" refrigerant for CFC-12?
What is the replacement refrigerant for CFC-12 in household refrigerators?
What can be determined by taking an accurate temperature and pressure reading of a container holding a recovered refrigerant?
Check for non-condensables and the type of refrigerant.
When doing a non-condensables check, a recovery cylinder should stabilize in temperature before any readings are taken. Why?
To find the correct pressure for that temperature on a T/P chart.
What is the internal pressure of CFC-12 refrigerant stored at 75 deg. F?
What is the exception to the rule that says that someone servicing and appliance must have at least one self-contained recovery machine available at their place of business?
Only when the person is working on a small appliance.
Ammonia, hydrogen, and water can be found in the refrigerators in some campers and other recreational vehicles. Should these compounds be recovered with EPA approved recovery equipment?
May the nitrogen used for purging or pressurizing a system be vented to the atmosphere?
When may a technician recover only 80% of the refrigerant in a small appliance?
In a system dependent recovery with a non-operating compressor?
May a technician use a passive recovery machine for recovery from a domestic refrigerator?
What requirements are placed on recovery machines built after November 15, 1993?
Must be able to recover 80% of the refrigerant if the compressor is inoperative or 90% if the compressor is operative. Must be EPA certified.
When using a recovery machine manufactured after November 15, 1993, what percentage of the refrigerant must be recovered in a household refrigerator with an operating compressor? What percentage if the compressor is NOT operating?
Is a certified technician responsible for future changes in EPA regulations?
What type of certification is required to purchase CFC and HCFC refrigerants?
What must be done with any regulated refrigerant vented from a graduated charging cylinder?
What first step must you always take before starting a recovery of refrigerant form any equipment?
Check which refrigerant is being used.
What is a "system-dependent" recovery machine?
System dependent recovery machines rely on the compressor of the system being serviced, or the pressure of the refrigerant to pump the refrigerant into a recovery drum.
Describe a system-dependent (passive) recovery process for small appliances.
Evacuate or cool a cylinder. Connect the high and low hoses to the system. Pull refrigerant into the cylinder with vacuum or the low tank pressure.
What two conditions require that you access both the high and low side of the system for refrigerant recovery?
When there is an inoperative compressor on the system or when necessary to reach required recovery levels.
What are the benefits of accessing the low and high side access valves when recovering refrigerant from a system with an inoperative compressor?
It speeds up recovery, improves efficiency and may be necessary to reach required recovery levels.
How should you access the system and should you run the compressor when using a system-dependent (passive) recovery on a refrigerator with an operable compressor?
Access the high side and run the compressor.
Which access valve (s) should you connect to when recovering from a system with an operating compressor and a completely restricted capillary tube?
When using a self-contained (active) recovery device, what two conditions can cause excessive pressure on the recovery machine's high side?
A recovery container that is not properly evacuated or one that has unopened valve.
Why should defrost heaters be turned on during a recovery from a small appliance?
To speed up refrigerant release from the oil.
When should entrapped refrigerant from oil be recovered?
Any time oil is removed from a large system and on small appliances when using system dependent recovery with a non-operating compressor.
What does striking the appliance compressor do during a recovery?
Helps to free refrigerant that may be trapped in the oil.
A recovery machine should be checked daily for what?
Can a standard vacuum pump be used as a recovery machine?
In theory yes, but unlikely. First it would have to be certifiable, second it would have to be connected to a non-pressurized recovery container.
Should technicians ever mix refrigerants in the field?
How should you recover refrigerant that is different from the refrigerant you usually recover?
Different refrigerants must be placed in recovery vessels containing the same type of refrigerant.
What can a reclaimer do with any mixed refrigerant you ship to them?
They may either refuse to process and return it at owner's expense or agree to destroy the refrigerant for a substantial fee.
To ship recovered refrigerant you must label the container and complete all necessary paperwork. What else should you do?
Use DOT approved cylinders.
What federal agency sets the standards for portable refillable tanks or containers used to ship CFC or HCFC refrigerants?
Department of Transportation (DOT).
Safety glasses and butyl-lined gloves should be worn fro what procedures?
When you are connecting and disconnecting hoses.
Piercing valves are used for what purpose?
To allow access to the sealed system for recovery.
On what materials are piercing valves used?
Copper or aluminum refrigerant lines.
What should be done to a piercing type Schrader valve after it is installed on a charged system?
It should be capped after any service procedure.
Why should solder-less type piercing valves be removed after completion of repairs?
What are the critical maintenance checks done to a Schrader valve?
Periodically checked for leaks and replaced if damaged.
What does a pungent odor detected after opening a system mean?
It might mean acids are present due to a compressor burnout.
What do you do if the oil is contaminated?
Tubing flushing might be required.
What system pressure would indicate a recovery should not be performed?
What are the current methods used to monitor the 80% fill level in a recovery tank?
Floats, thermistor-type sensors and weighing scales.
Why do large refrigerant leaks cause suffocation?
Refrigerants will replace air in a confined space leading to possible oxygen starvation.
Before entering an area of a large leak of refrigerant what apparatus must be worn?
Self contained breathing apparatus.
What should be done if a large leak occurs and no breathing apparatus is available?
Ventilate the space and leave the area.
Which acids are formed when refrigerant touches sources of high heat?
Hydrochloric and hydrofluoric acids and phosgene gas.
What safety component must be used whenever dry nitrogen is used to pressurize a system?
Nitrogen tanks should be equipped with a regulator.
What information does DOT require when shipping refrigerant cylinders?
Shipping papers must indicate the refrigerant type and number of cylinders.
Which government agency sets the standards for refillable refrigerant cylinders used to transport CFC and HCFC refrigerants?
Department of Transportation (DOT).
What component is always replaced after a a system is opened for service?
What is the purpose of the moisture indicator in a sight glass?
To permit a check of moisture content in the system.
What does "back-seating" a suction valve do?
Allows flow through the main line while closing the access port.
What will non-condensables do to the pressures in a refrigerant circuit?
Increase discharge pressure.
What causes oil foaming in a system and where does it normally occur?
Oil that is mixed with refrigerant will foam in the compressor crankcase.
What system failures require taking an oil sample?
Compressor burnout or if the unit has had a leak.
A vacuum pump that is too large can cause what problem?
It can cause moisture to freeze in the system?
Where is a receiver typically installed on a system?
At the outlet of the condenser.
What will be the boiling temperature of HFC-134a be at 0 PSIG?
Is it a requirement that recovery machines contain an oil separator?
Which refrigerant is typically used on a residential split system air conditioner?
Is the refrigerant leaving a receiver a liquid or a gas? Is it at a high or low pressure?
What is the initial charging method of a system when the charge is specified at 70 pounds?
Is the receiver on the high or low side of a system?
What is the minimum recommended capability (measured in microns) of a vacuum pump used for evacuations?
Should pull a vacuum of 500 microns.
What is the pressure of a CFC-12 machine at 72 deg. F while the machine is idle?
What is the preferred unit of measurement for checking a deep vacuum?
Where is an accumulator located in a refrigeration system?
On the suction line before the compressor.
To prevent freezing of any moisture in a CFC-12 system, vapor should first be charged until the pressure is at what level?
What gas should be used during an evacuation to increase pressure to prevent freezing?
What is the purpose of a compressor heater?
To reduce the amount of refrigerant in the lubricating oil.
How is moisture remaining from an evacuation removed from the refrigerant in a system?
What is the preferred method of leak checking a built-up system prior to charging?
What would a technician initially look for during a visual inspection of a leaking hermetic system?
Stains around tubing and fittings.
What is typically indicated by excessive superheat on a high-pressure system?
Undercharged system, possibly the result of a leaky system.
Which refrigerant should be used for a trace charge during leak detection?
How do you leak check an HFC-134a system with a partial charge (no HFC-134a detector available)?
Recover remaining 134a, pressurize the system with nitrogen and a trace charge of R-22 so you can use an HCFC electronic leak detector.
For what purpose are soap bubbles used in leak checking?
For a visual check for leaks.
Shaft seals on an open type compressor are susceptible to what failures?
What leak rate is permissible on industrial and process refrigeration?
Effective 6/14/93, any leak rate of 35% or more on equipment with 50 lbs. of charge or more must be repaired. Less than 35% is permissible.
What leak rate is permissible on equipment (other than industrial or process equipment) that contains more that 50 lbs. of refrigerant?
What is the easiest way to check the type of refrigerant used in a packaged rooftop system?
By the equipment data plate.
Refrigerant will recover fastest in which phase, liquid or vapor?
Which refrigerant line should a recovery machine be attached to in order to recover liquid refrigerant from a system?
After a liquid recovery, what must be done with the vapor still in the system?
Vapor recovery bust be performed.
Recovering in a vapor phase reduces unwanted loss of what?
Oil and unwanted contaminants from the system to the recovery machine and recovery drum.
On a high pressure system recovery, should the recovery cylinder be heated or cooled?
What must be done to a recovery machine when changing to a different refrigerant?
Clean out all residual refrigerant, change oil, replace filters, evacuate machine by pump-out or another machine.
What besides filters must periodically be changed out on a recovery machine?
Recovered refrigerant can contain oil and acids. Name another compound found in refrigerants?
What is the water source for a condensing coil on a water-cooled recovery machine?
What access location should you use when recovering from an air cooled system with its condenser several feet above the evaporator?
What access location should you use when recovering from a system with its condenser below the evaporator?
Before using a recovery unit, the technician should check service valve positions and check the recovery unit oil level. What additional step must be taken?
All solenoid valves should be open.
What is the primary purpose for using hand valves or self-sealing hoses when using a gauge set?
To prevent loss of refrigerant when connecting and disconnecting hoses.
What can cause recovery equipment with a hermetic compressor to overheat when drawing a deep vacuum?
No airflow over the compressor body or no suction gas flow over the internal motors, or a combination of the two.
What is the reason for not operating a hermetic refrigeration compressor while it is in a deep vacuum?
To prevent overheating the compressor motor.
What is the reason for not starting a reciprocating compressor with its discharge service valve closed?
To prevent overheating the compressor motor.
When can a "system-dependent" recovery device be used?
On small appliances as long as the device meets EPA standards and the technician adheres to the servicing procedures specified for the recovery equipment. Cannot be used on systems with more than 15 lbs. of refrigerant.
What vacuum level must you reach when recovering from a system with 38 pounds of R-502 using a recovery machine manufactured in 1995?
What is EPA's definition of a "major repair"?
Any repair that involves the removal of the compressor, evaporator, condenser, or any auxiliary heat exchanger coil.
Prior to making a major repair, what vacuum level must you pull when using recovery equipment manufactured in 1996 on a unit with 215 lbs. of CFC-12?
What vacuum level must you pull when using recovery equipment manufactured in 1992 when disposing of an appliance containing 12 lbs. of R-500?
Under what circ*mstances may a technician recover the CFC refrigerant in an appliance to atmospheric pressure only?
if leaks are in the system or if recovery to target levels would contaminate the refrigerant.
What procedure should be performed on an empty recovery cylinder before it is used for storing recovered refrigerant?
It must be evacuated of all non-condensables.
What may legally be done with the refrigerant recovered from a system in order to replace a condenser coil?
Reused in the original system or transferred to another system with the same owner after it is checked so that it is free of non-condensables.
When servicing an operating unit with a receiver, where should the recovery hoses be attached to the unit?
In order to recover from a system with parallel compressors, the individual compressors must be isolated. Why?
It isolates the refrigerant that must be recovered from the rest of the system.
Which refrigerant (s) require and equipment room monitor per ASHRAE Standard 15?
What protection is mandatory to protect a system against damage from excessive pressure?
A pressure relief device.
Are multiple relief valves connected in series or parallel?
Why is the use of a regulator required when using dry nitrogen?
To limit the outlet pressure of the nitrogen cylinder.
How can ice be removed from a sight glass?
Cleaned with an alcohol spray.
How high should you pressurize an idle low pressure chiller to prevent air accumulation?
Slightly above atmospheric pressure.
What effect does air in a chiller have on head pressure?
What system failures require taking and oil sample?
A leak or major component failure (compressor burnout).
Why must water be circulated through a chiller during refrigerant recovery?
To prevent freeze-up of the water as pressure is reduced on the refrigerant.
What is the lowest access valve on a low pressure chiller?
The evaporator charging valve.
Where is a centrifugal chiller's rupture disk attached?
What is the typical pressure setting for a low pressure chiller's rupture disk?
Where is the outlet of a rupture disk discharged?
How is a chiller typically charged?
Liquid through the evaporator charging valve.
What minimum saturation temperature needs to be achieved before liquid is charged into a chiller?
Above freezing, typically 36 deg. F.
To prevent freezing of water when charging a chiller, what pressure should be reached with vapor before using liquid CFC-11?
What could result from liquid refrigerant being charged into a chiller that is holding a 29 inch Hg. vacuum?
Can cause system water to freeze.
What function is served by a purge unit on a chiller?
Minimize the effects of contamination. To remove non-condensables.
What is the most likely cause of air leaks into a chiller refrigerant circuit?
How is a purge unit connected on a low pressure chiller?
The inlet of the purge unit is typically connected to the top of the condenser.
Where is the suction of a purge unit connected?
The inlet of the purge unit is typically connected to the top of the condenser.
What is a high efficiency purge unit?
It removes non-condensables that contain a low percentage of refrigerant. This adds to the value of the purge drum in refrigerant containment.
Shaft seals on an open type compressor are susceptible to what failures?
Purge units work best when they are not needed. How can purge unit operating time be reduced?
By regular leak checking and repairing any leaks on a regular schedule.
What is the maximum pressure that can be used when leak checking a low pressure chiller?
10 PSIG on low pressure equipment that utilizes a rupture disk.
What is the preferred method of leak checking a charged low pressure chiller?
By increasing the refrigerant pressure using an external heat source or running hot water through the chiller tubes not to exceed 10 PSIG.
Where should you check for leaks between a chiller refrigerant tube and the water box?
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.
What is a hydrostatic tube test kit used for?
To check for leaks in a chiller tubes.
What leak rate is permissible on industrial and process refrigeration?
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.
What leak rate is permissible on equipment other than industrial and process equipment?
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.
According to ASHRAE 3-1990, what rise is permitted in vacuum level during a standing vacuum test?
Starting at 1mm of Hg., after 12 hours the vacuum reading should not increase to more than 2.5 mm of Hg.
List two steps to reduce the run time of a purge unit.
Regular leak checks and repair any leaks.
Why should the water side of the evaporator and condenser be drained before recovering refrigerant from a chiller suspected of having tube leaks?
To prevent moisture form being drawn into the refrigerant circuit.
If a purge unit is operating excessively, what problem can you expect to find?
What condition would cause continuous excessive moisture collection in the purge unit of a low pressure refrigeration system?
Leaks between the refrigerant circuit and the water circuit.
Why should oil be warmed prior to removal from a low pressure chiller?
To vaporize any liquid refrigerant that might be trapped in the oil.
After liquid recovery, what must be done with the vapor still in the system?
Vapor recovery must be performed.
Is recovery of refrigerant from a low pressure appliance typically started with liquid or vapor?
Start with liquid removal.
Where is the connection made for the water supply used on a water cooled recovery unit?
What should be the maximum pressure on the discharge of a recovery machine for low pressure systems?
10 PSIG, because the rupture disk is set to open at 15 PSIG.
What should be done with the water pumps during a recovery form a low pressure chiller?
What is EPA's definition of a "major repair"?
Any repair that involves the removal of the compressor, evaporator, condenser, or any auxiliary heat exchange coil.
What recovery vacuum must be met on a low pressure appliance using a machine built in 1992?
Why should you wait a few minutes after reaching the required recovery vacuum on an appliance to see if pressure rises?
To see if refrigerant is still trapped in the system.
Under what circ*mstances may the recovery from an appliance be stopped without reaching the prescribed level?
If the recovery would contaminate the refrigerant being recovered. (this level cannot exceed 0 PSIG.)
Is it a requirement that recycling and recovery equipment be capable of handling more than one refrigerant?
Is it permissible to warm the refrigerant under EPA's regulations to pressurize a low pressure system to do a non-major repair?
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?
25 inches of Hg, 25 mm of Hg. Absolute (equal to about 29 inches of Hg.)
A vacuum pump that is too large for a particular system can cause what problem?
It can cause moisture to freeze in the system.
How can you prevent moisture from freezing during dehydration?
You can raise the pressure with nitrogen and allow the ice to melt, then continue with the evacuation.
Are multiple relief valves connected in series or parallel?
ASHRAE Standard 15 covers refrigerant level monitoring for what refrigerants?
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?
May not exceed the TLV-TWA. (Threshold limit value-Time weighted average.)
List four safety procedures that should be followed when working with liquid low pressure refrigerant.
4. Wear safety glasses.
What is the toxicity and flammability rating of HCFC-123 per ASHRAE Standard 34?
