Which factor does not affect the speed of evacuation? (2024)

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.

Term

What are the typical uses of the center port of gauge set?

Definition

Used during evacuation, charging and recovery procedures.

Term

What color are the gauges on a manifold gauge set?

Definition

Low pressure is blue, High pressure is red.

Term

What are the typical ranges of pressure measurements used on the gauges of a manifold gauge set?

Definition

High side is 0 to 500 PSIG; Low side is 0 to 350 PSIG and 0 to 30 in. Hg below atmospheric pressure.

Term

Is the refrigerant leaving a condenser at a high or low pressure? Is it a liquid or a gas?

Definition
Term

Is the refrigerant entering the expansion valve (variable metering device) a liquid or gas?

Definition
Term

Is the pressure of the refrigerant entering the compressor high or low?

Definition
Term

Where in a refrigerant circuit does a liquid boil to absorb heat?

Definition
Term

The refrigerant in the suction line is a gas that has been heated above its saturation. What is this condition called?

Definition
Term

What can cause liquid refrigerant to migrate to a compressor crankcase?

Definition

If the compressor is located in the coldest location in the circuit.

Term

List two conditions that can quickly damage a compressor that is starting to run?

Definition

Operating while in a deep vacuum or when the service valves are closed.

Term

What system failures require taking an oil sample?

Definition

A compressor burnout or if the unit has had a leak.

Term

Is flushing with refrigerant an acceptable tube cleaning method?

Definition
Term

In addition to preventing and repairing leaks, what else should a technician do to conserve refrigerant?

Definition

Recover and recycle used refrigerants.

Term

What factors affect the speed of an evacuation?

Definition

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.

Term

How should gauge set hoses be sized for use in evacuating a system?

Definition

Use the shortest length and the largest diameter possible for the quickest evacuation. At least as large as the vacuum pump inlet.

Term

When evacuating, what is the benefit of using short hoses with large diameters?

Definition

Reduces emissions, pressure drop and evacuation time.

Term

which connection determines the preferred size of hoses used with a vacuum pump?

Definition
Term

As the capacity and suction hose size increase, what happens to the time needed for an evacuation?

Definition
Term

What purpose is served by heating a system during dehydration?

Definition

To speed up moisture removal.

Term

Does a thorough evacuation remove moisture from a system?

Definition
Term

What can happen to oil in the compressor if the moisture is left in an operating system?

Definition

The oil will form hydrofluoric and hydrochloric acids which will corrode the internal parts of the system.

Term

What is the result of over-evacuating a system?

Definition
Term

How can a system be leak checked using a low pressure gauge?

Definition

Vacuum reading will rise when vacuum pump is turned off.

Term

How close should the vacuum gauge be connected to the vacuum pump during evacuation?

Definition
Term

When measuring the vacuum of a system being evacuated, the system must be isolated. What must be done to the vacuum pump?

Definition

Turn it off and valve it off.

Term
Definition

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.

Term

How much ozone can a chlorine atom destroy in the stratosphere?

Definition

One atom can destroy 100,000 ozone molecules.

Term

What is Ozone Depletion Potential (ODP)?

Definition

The ability of any chemical to deplete the ozone layer.

Term
Definition
Term

Which refrigerants are CFC's?

Definition
Term

Which chemical in the CFC refrigerants does the most damage to the ozone layer?

Definition
Term
Definition

Hydrochlorofluorocarbons.

Term

Which refrigerants are HCFC's?

Definition
Term

Which is more harmful to the ozone layer, a CFC or an HCFC?

Definition
Term

What is it about CFC's that make them more harmful to the stratosphere?

Definition

Chemical strength, they will not breakdown in the lower atmosphere.

Term
Definition

A fluorocarbon that contains no chlorine.

Term

Which refrigerants are HFC's?

Definition
Term

What is the ODP of the HFC refrigerant?

Definition
Term

Which refrigerants contain chlorine?

Definition
Term

Which refrigerants have high ODP?

Definition
Term

Which refrigerants have low ODP?

Definition
Term

What is an azeotrope refrigerant?

Definition

A mixture of two or more compounds where the mixture behaves like a single chemical.

Term

Is one of the components of R-500 a CFC?

Definition
Term

Does stratospheric ozone help or hurt the work of the earth's protective shield?

Definition
Term

What chemical in the stratosphere tells us ozone depletion is occurring?

Definition
Term

How do we know the chlorine in the stratosphere is coming from CFC's?

Definition

The increase in chlorine and fluorine present in the stratosphere, matches the increase in emissions of CFC's.

Term

How do we know CFC's get to the stratosphere?

Definition

From high altitude air sampling measurements.

Term

What role does the ozone layer play in protecting the earth?

Definition

It blocks much of the harmful ultraviolet radiation (uv-b).

Term

What are the effects on health from increased ultraviolet radiation?

Definition

Skin cancer, cataracts, human immunity is reduced.

Term

What are the effects on the environment?

Definition

Timber growth is reduced, crop yields lowered, marine life and the food chain are impaired.

Term

Is ozone depletion a problem for the United States only or a global problem?

Definition
Term

What is the Montreal Protocol?

Definition

A treaty that called for the reduction of production of CFC's.

Term

The Montreal Protocol calls for the regulation of what chemicals?

Definition

Ozone depleting compounds, CFC's, HCFC's, and Halons.

Term

On what date was the production and importation of all CFC's phased out?

Definition

In the U.S., after December 31, 1995.

Term

Where will we get replacements?

Definition

Through recovery of existing refrigerants.

Term

What steps are called for by the Clean Air Act?

Definition

Taxes on production and use, standards set for the recovery of refrigerants.

Term

What is prohibited by the Clean Air Act?

Definition
Term

Do state and local laws have priority over federal law? Can they be less strict?

Definition

No. Cities or states can create their own laws but they must be at least as strict as federal laws.

Term

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?

Definition

Allows states and municipalities to create their own laws to prevent and monitor the release of CFC and HCFC materials into the atmosphere.

Term

By recovering refrigerants, we ensure adequate supplies and prevent venting. What else does the recovery of refrigerants accomplish?

Definition

Prevents stratospheric ozone depletion.

Term

The Clean Air Act phases out CFC/HCFC production and prohibits venting. What else does it require?

Definition

Standards to be set for recovery of all refrigerants prior to appliance service and disposal.

Term

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?

Definition

Knowingly venting CFC's, HCFC's and their substitutes.

Term

Which refrigerants must be recovered prior to opening a system?

Definition

All refrigerants as of 11-15-1995.

Term

What releases of a CFC and HCFC are violations of the Clean Air Act?

Definition

Any knowingly vented refrigerants.

Term

On what date did it become illegal to vent CFC and HCFC refrigerants?

Definition
Term

Which appliances are covered by Section 608?

Definition

Any device which contains and uses a class 1 or class 2 substance as a refrigerant and is used for household or commercial purposes.

Term

What is the primary reason the EPA requires a service aperture or process stub on all appliances?

Definition

For adding or removing refrigerant from the appliance.

Term

Who sets the regulations for recovery machines?

Definition
Term

What is a "self-contained" recovery machines?

Definition

A recovery machine that has its own compressor to pump refrigerant out of the system.

Term

Is HCFC-123 a "low or "high" pressure refrigerant?

Definition
Term

Is CFC-12 a "low" or "high" pressure refrigerant?

Definition
Term

What is the smallest container in which refrigerants may be sold to a Section 608 certified technicians.

Definition
Term

What must you do to the refrigerant in an appliance before disposing of the appliance?

Definition

Recover refrigerant or verify that the refrigerant was previously recovered.

Term

Who is responsible for removing the refrigerant from household refrigerators prior to disposal?

Definition

The final person in the disposal chain. (Scrap metal recyclers, landfill owner, etc)

Term

What is the penalty for violation of the Clean Air Act?

Definition

Fines up to $27,500 per violation per day and possible loss of technician certification.

Term

How much is the bounty for information leading to a conviction?

Definition
Term

What ca happen if a technician cannot demonstrate an ability to use recovery or recycling equipment?

Definition

May result in revocation of the technician's certification.

Term

What is the name of the process that removes refrigerant from a system and stores it without testing or processing?

Definition
Term

What is the name for the process that removes moisture and acids from refrigerant but does not test the refrigerant?

Definition
Term

What is the name for the process that removes moisture and acids from refrigerant and also chemically tests the refrigerant?

Definition
Term

What must be done with reclaimed refrigerant before it can be legally resold?

Definition

Chemically tested to ARI Standard 700, the purity level of factory new refrigerant.

Term

What is the preferred instrument for detecting small leaks?

Definition

Electronic leak detector and Ultrasonic detector.

Term

What is an inert gas typically used in leak detection?

Definition
Term

What is typically indicated by a dehydrated system failing to hold a vacuum?

Definition
Term

What should be done when recovering the refrigerant form a system where the refrigerant has been improperly mixed?

Definition

Recover into a separate container?

Term

Can mixed refrigerants be reclaimed?

Definition
Term

What precautions should be taken when recovering refrigerant from systems with multiple service valves?

Definition

Insure that liquid is not trapped between service valves.

Term

What is the effect of low ambient temperature on the time required to complete a recovery of refrigerant?

Definition
Term

Technicians must explain to customers that recovery is necessary and it is required by law. What else should the technician tell the customer?

Definition

That all service personnel are duty bound to follow the law and protect the environment.

Term

What is different about any leaks in systems charged with a blended refrigerant?

Definition

Because they are blended, the ingredients will leak at different rates.

Term

What is "temperature glide"?

Definition

A family of lines depicting pressure versus temperature curve.

Term
Definition

A blend of three different refrigerants.

Term

How should systems using blended refrigerants be charged?

Definition

In liquid form into the high side of the system.

Term

Is there a "drop-in" refrigerant for CFC-12?

Definition
Term

How do you leak check an HFC-134a system with a partial charge (no HFC-134a detector available)?

Definition

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.

Term

What is the preferred oil to be used with HFC-134a?

Definition
Term

Can ester based oils be mixed with other oils?

Definition
Term

What does "hygroscopic" mean?

Definition

Oil that absorbs moisture easily.

Term

What lubricant is recommended for use with a ternary blend?

Definition

Depends on the blend: For HCFC's-Alkylbenze, For HFC's-Ployolester.

Term

Safety glasses and butyl-lined gloves should be worn for what procedures?

Definition

When operating recovery or recycling devices and when handling and refilling refrigerant cylinders.

Term

What safety component must be used whenever dry nitrogen is used to pressurize a system?

Definition
Term

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?

Definition
Term

What is a Material Safety Data Sheet?

Definition

A sheet the states the safety ratings and precautions to be taken for use and handling of chemicals.

Term

What safety classification within the ASHRAE standard is the most safe?

Definition
Term

What is caused by tie inhaling of refrigerant vapors?

Definition

Heart irregularities or Asphyxia.

Term

What is the major causes of death involving refrigerants?

Definition
Term

What breathing problem can be caused by CFC-12?

Definition
Term

How can ice be removed from a sight glass?

Definition
Term

What must be done with a badly corroded relief valve?

Definition
Term

Where can you find the allowable test pressure on a system?

Definition
Term

Can oxygen be used to check for leaks? If not, why not?

Definition

No. Oxygen in the presence of oil under high pressure can be explosive.

Term

What is the likely result of heating a recovery cylinder with an open flame?

Definition

Refrigerant will decompose into a toxic material, venting of refrigerant int the atmosphere or the tank may explode.

Term

What is the primary purpose of a disposable cylinder?

Definition

For virgin refrigerant from the manufacturer.

Term

To what internal pressure should a disposable cylinder be reduced to for disposal?

Definition

Reduced to at least 0 PSIG.

Term

Should you ever use a disposable cylinder for refrigerant recovery?

Definition
Term

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?

Definition

Puncture the container before disposal.

Term

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?

Definition

Properly secured at all times.

Term

What is the proper color code for recovery cylinders?

Definition
Term

What is the maximum percent by weight that a cylinder may be filled?

Definition
Term

What can happen if a cylinder is overfilled?

Definition

Hydrostatic pressure could cause the cylinder to explode.

Term

List three methods for measuring the fill level of a recovery cylinder.

Definition

Floats, thermistor type sensors, and weighing scales.

Term

Wow often must reusable cylinders be hydrostatically tested?

Definition
Term

Why must only refillable cylinders be used for transport?

Definition

Federal code of regulations title 49 (parts 100-177) states this.

Term

What must be affixed to a refrigerant cylinder prior to its shipment to a reclaimer?

Definition
Term

What is the purpose of a DOT classification tag?

Definition

For transportation purposes.

Term

What is the correct shipping position for a refrigerant cylinder?

Definition

In a vertical or upright position with their valves at the top.

Term

What is the EPA definition of a small appliance?

Definition

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.

Term

Does the EPA require the repair of leaks on small appliances?

Definition

Repair of leaks on small appliances is not required, but leaks should be repaired whenever possible.

Term

What EPA certification type must technicians have to service any appliance that EPA calls a "small appliance?"

Definition
Term

What service aperture may be used on small appliance?

Definition

Access tubes or process tubes.

Term

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?

Definition

Low-loss fitting. (shut-off valve)

Term

What is the primary purpose for using hand valves or self-sealing hoses when using a gauge set?

Definition

To prevent loss of refrigerant.

Term

Which refrigerants must be recovered under Section 608 of the EPA regulations?

Definition

CFC, HCFC and HFC refrigerant.

Term

Is there a "drop-in" refrigerant for CFC-12?

Definition
Term

What is the replacement refrigerant for CFC-12 in household refrigerators?

Definition
Term

What can be determined by taking an accurate temperature and pressure reading of a container holding a recovered refrigerant?

Definition

Check for non-condensables and the type of refrigerant.

Term

When doing a non-condensables check, a recovery cylinder should stabilize in temperature before any readings are taken. Why?

Definition

To find the correct pressure for that temperature on a T/P chart.

Term

What is the internal pressure of CFC-12 refrigerant stored at 75 deg. F?

Definition
Term

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?

Definition

Only when the person is working on a small appliance.

Term

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?

Definition
Term

May the nitrogen used for purging or pressurizing a system be vented to the atmosphere?

Definition
Term

When may a technician recover only 80% of the refrigerant in a small appliance?

Definition

In a system dependent recovery with a non-operating compressor?

Term

May a technician use a passive recovery machine for recovery from a domestic refrigerator?

Definition
Term

What requirements are placed on recovery machines built after November 15, 1993?

Definition

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.

Term

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?

Definition
Term

Is a certified technician responsible for future changes in EPA regulations?

Definition
Term

What type of certification is required to purchase CFC and HCFC refrigerants?

Definition
Term

What must be done with any regulated refrigerant vented from a graduated charging cylinder?

Definition
Term

What first step must you always take before starting a recovery of refrigerant form any equipment?

Definition

Check which refrigerant is being used.

Term

What is a "system-dependent" recovery machine?

Definition

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.

Term

Describe a system-dependent (passive) recovery process for small appliances.

Definition

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.

Term

What two conditions require that you access both the high and low side of the system for refrigerant recovery?

Definition

When there is an inoperative compressor on the system or when necessary to reach required recovery levels.

Term

What are the benefits of accessing the low and high side access valves when recovering refrigerant from a system with an inoperative compressor?

Definition

It speeds up recovery, improves efficiency and may be necessary to reach required recovery levels.

Term

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?

Definition

Access the high side and run the compressor.

Term

Which access valve (s) should you connect to when recovering from a system with an operating compressor and a completely restricted capillary tube?

Definition
Term

When using a self-contained (active) recovery device, what two conditions can cause excessive pressure on the recovery machine's high side?

Definition

A recovery container that is not properly evacuated or one that has unopened valve.

Term

Why should defrost heaters be turned on during a recovery from a small appliance?

Definition

To speed up refrigerant release from the oil.

Term

When should entrapped refrigerant from oil be recovered?

Definition

Any time oil is removed from a large system and on small appliances when using system dependent recovery with a non-operating compressor.

Term

What does striking the appliance compressor do during a recovery?

Definition

Helps to free refrigerant that may be trapped in the oil.

Term

A recovery machine should be checked daily for what?

Definition
Term

Can a standard vacuum pump be used as a recovery machine?

Definition

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.

Term

Should technicians ever mix refrigerants in the field?

Definition
Term

How should you recover refrigerant that is different from the refrigerant you usually recover?

Definition

Different refrigerants must be placed in recovery vessels containing the same type of refrigerant.

Term

What can a reclaimer do with any mixed refrigerant you ship to them?

Definition

They may either refuse to process and return it at owner's expense or agree to destroy the refrigerant for a substantial fee.

Term

To ship recovered refrigerant you must label the container and complete all necessary paperwork. What else should you do?

Definition

Use DOT approved cylinders.

Term

What federal agency sets the standards for portable refillable tanks or containers used to ship CFC or HCFC refrigerants?

Definition

Department of Transportation (DOT).

Term

Safety glasses and butyl-lined gloves should be worn fro what procedures?

Definition

When you are connecting and disconnecting hoses.

Term

Piercing valves are used for what purpose?

Definition

To allow access to the sealed system for recovery.

Term

On what materials are piercing valves used?

Definition

Copper or aluminum refrigerant lines.

Term

What should be done to a piercing type Schrader valve after it is installed on a charged system?

Definition

It should be capped after any service procedure.

Term

Why should solder-less type piercing valves be removed after completion of repairs?

Definition
Term

What are the critical maintenance checks done to a Schrader valve?

Definition

Periodically checked for leaks and replaced if damaged.

Term

What does a pungent odor detected after opening a system mean?

Definition

It might mean acids are present due to a compressor burnout.

Term

What do you do if the oil is contaminated?

Definition

Tubing flushing might be required.

Term

What system pressure would indicate a recovery should not be performed?

Definition
Term

What are the current methods used to monitor the 80% fill level in a recovery tank?

Definition

Floats, thermistor-type sensors and weighing scales.

Term

Why do large refrigerant leaks cause suffocation?

Definition

Refrigerants will replace air in a confined space leading to possible oxygen starvation.

Term

Before entering an area of a large leak of refrigerant what apparatus must be worn?

Definition

Self contained breathing apparatus.

Term

What should be done if a large leak occurs and no breathing apparatus is available?

Definition

Ventilate the space and leave the area.

Term

Which acids are formed when refrigerant touches sources of high heat?

Definition

Hydrochloric and hydrofluoric acids and phosgene gas.

Term

What safety component must be used whenever dry nitrogen is used to pressurize a system?

Definition

Nitrogen tanks should be equipped with a regulator.

Term

What information does DOT require when shipping refrigerant cylinders?

Definition

Shipping papers must indicate the refrigerant type and number of cylinders.

Term

Which government agency sets the standards for refillable refrigerant cylinders used to transport CFC and HCFC refrigerants?

Definition

Department of Transportation (DOT).

Term

What component is always replaced after a a system is opened for service?

Definition
Term

What is the purpose of the moisture indicator in a sight glass?

Definition

To permit a check of moisture content in the system.

Term

What does "back-seating" a suction valve do?

Definition

Allows flow through the main line while closing the access port.

Term

What will non-condensables do to the pressures in a refrigerant circuit?

Definition

Increase discharge pressure.

Term

What causes oil foaming in a system and where does it normally occur?

Definition

Oil that is mixed with refrigerant will foam in the compressor crankcase.

Term

What system failures require taking an oil sample?

Definition

Compressor burnout or if the unit has had a leak.

Term

A vacuum pump that is too large can cause what problem?

Definition

It can cause moisture to freeze in the system?

Term

Where is a receiver typically installed on a system?

Definition

At the outlet of the condenser.

Term

What will be the boiling temperature of HFC-134a be at 0 PSIG?

Definition
Term

Is it a requirement that recovery machines contain an oil separator?

Definition
Term

Which refrigerant is typically used on a residential split system air conditioner?

Definition
Term

Is the refrigerant leaving a receiver a liquid or a gas? Is it at a high or low pressure?

Definition
Term

What is the initial charging method of a system when the charge is specified at 70 pounds?

Definition
Term

Is the receiver on the high or low side of a system?

Definition
Term

What is the minimum recommended capability (measured in microns) of a vacuum pump used for evacuations?

Definition

Should pull a vacuum of 500 microns.

Term

What is the pressure of a CFC-12 machine at 72 deg. F while the machine is idle?

Definition
Term

What is the preferred unit of measurement for checking a deep vacuum?

Definition
Term

Where is an accumulator located in a refrigeration system?

Definition

On the suction line before the compressor.

Term

To prevent freezing of any moisture in a CFC-12 system, vapor should first be charged until the pressure is at what level?

Definition
Term

What gas should be used during an evacuation to increase pressure to prevent freezing?

Definition
Term

What is the purpose of a compressor heater?

Definition

To reduce the amount of refrigerant in the lubricating oil.

Term

How is moisture remaining from an evacuation removed from the refrigerant in a system?

Definition
Term

What is the preferred method of leak checking a built-up system prior to charging?

Definition
Term

What would a technician initially look for during a visual inspection of a leaking hermetic system?

Definition

Stains around tubing and fittings.

Term

What is typically indicated by excessive superheat on a high-pressure system?

Definition

Undercharged system, possibly the result of a leaky system.

Term

Which refrigerant should be used for a trace charge during leak detection?

Definition
Term

How do you leak check an HFC-134a system with a partial charge (no HFC-134a detector available)?

Definition

Recover remaining 134a, pressurize the system with nitrogen and a trace charge of R-22 so you can use an HCFC electronic leak detector.

Term

For what purpose are soap bubbles used in leak checking?

Definition

For a visual check for leaks.

Term

Shaft seals on an open type compressor are susceptible to what failures?

Definition
Term

What leak rate is permissible on industrial and process refrigeration?

Definition

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.

Term

What leak rate is permissible on equipment (other than industrial or process equipment) that contains more that 50 lbs. of refrigerant?

Definition
Term

What is the easiest way to check the type of refrigerant used in a packaged rooftop system?

Definition

By the equipment data plate.

Term

Refrigerant will recover fastest in which phase, liquid or vapor?

Definition
Term

Which refrigerant line should a recovery machine be attached to in order to recover liquid refrigerant from a system?

Definition
Term

After a liquid recovery, what must be done with the vapor still in the system?

Definition

Vapor recovery bust be performed.

Term

Recovering in a vapor phase reduces unwanted loss of what?

Definition

Oil and unwanted contaminants from the system to the recovery machine and recovery drum.

Term

On a high pressure system recovery, should the recovery cylinder be heated or cooled?

Definition
Term

What must be done to a recovery machine when changing to a different refrigerant?

Definition

Clean out all residual refrigerant, change oil, replace filters, evacuate machine by pump-out or another machine.

Term

What besides filters must periodically be changed out on a recovery machine?

Definition
Term

Recovered refrigerant can contain oil and acids. Name another compound found in refrigerants?

Definition
Term

What is the water source for a condensing coil on a water-cooled recovery machine?

Definition
Term

What access location should you use when recovering from an air cooled system with its condenser several feet above the evaporator?

Definition
Term

What access location should you use when recovering from a system with its condenser below the evaporator?

Definition
Term

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?

Definition

All solenoid valves should be open.

Term

What is the primary purpose for using hand valves or self-sealing hoses when using a gauge set?

Definition

To prevent loss of refrigerant when connecting and disconnecting hoses.

Term

What can cause recovery equipment with a hermetic compressor to overheat when drawing a deep vacuum?

Definition

No airflow over the compressor body or no suction gas flow over the internal motors, or a combination of the two.

Term

What is the reason for not operating a hermetic refrigeration compressor while it is in a deep vacuum?

Definition

To prevent overheating the compressor motor.

Term

What is the reason for not starting a reciprocating compressor with its discharge service valve closed?

Definition

To prevent overheating the compressor motor.

Term

When can a "system-dependent" recovery device be used?

Definition

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.

Term

What vacuum level must you reach when recovering from a system with 38 pounds of R-502 using a recovery machine manufactured in 1995?

Definition
Term

What is EPA's definition of a "major repair"?

Definition

Any repair that involves the removal of the compressor, evaporator, condenser, or any auxiliary heat exchanger coil.

Term

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?

Definition
Term

What vacuum level must you pull when using recovery equipment manufactured in 1992 when disposing of an appliance containing 12 lbs. of R-500?

Definition
Term

Under what circumstances may a technician recover the CFC refrigerant in an appliance to atmospheric pressure only?

Definition

if leaks are in the system or if recovery to target levels would contaminate the refrigerant.

Term

What procedure should be performed on an empty recovery cylinder before it is used for storing recovered refrigerant?

Definition

It must be evacuated of all non-condensables.

Term

What may legally be done with the refrigerant recovered from a system in order to replace a condenser coil?

Definition

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.

Term

When servicing an operating unit with a receiver, where should the recovery hoses be attached to the unit?

Definition
Term

In order to recover from a system with parallel compressors, the individual compressors must be isolated. Why?

Definition

It isolates the refrigerant that must be recovered from the rest of the system.

Term

Which refrigerant (s) require and equipment room monitor per ASHRAE Standard 15?

Definition
Term

What protection is mandatory to protect a system against damage from excessive pressure?

Definition

A pressure relief device.

Term

Are multiple relief valves connected in series or parallel?

Definition
Term

Why is the use of a regulator required when using dry nitrogen?

Definition

To limit the outlet pressure of the nitrogen cylinder.

Term

How can ice be removed from a sight glass?

Definition

Cleaned with an alcohol spray.

Term

How high should you pressurize an idle low pressure chiller to prevent air accumulation?

Definition

Slightly above atmospheric pressure.

Term

What effect does air in a chiller have on head pressure?

Definition
Term

What system failures require taking and oil sample?

Definition

A leak or major component failure (compressor burnout).

Term

Why must water be circulated through a chiller during refrigerant recovery?

Definition

To prevent freeze-up of the water as pressure is reduced on the refrigerant.

Term

What is the lowest access valve on a low pressure chiller?

Definition

The evaporator charging valve.

Term

Where is a centrifugal chiller's rupture disk attached?

Definition
Term

What is the typical pressure setting for a low pressure chiller's rupture disk?

Definition
Term

Where is the outlet of a rupture disk discharged?

Definition
Term

How is a chiller typically charged?

Definition

Liquid through the evaporator charging valve.

Term

What minimum saturation temperature needs to be achieved before liquid is charged into a chiller?

Definition

Above freezing, typically 36 deg. F.

Term

To prevent freezing of water when charging a chiller, what pressure should be reached with vapor before using liquid CFC-11?

Definition
Term

What could result from liquid refrigerant being charged into a chiller that is holding a 29 inch Hg. vacuum?

Definition

Can cause system water to freeze.

Term

What function is served by a purge unit on a chiller?

Definition

Minimize the effects of contamination. To remove non-condensables.

Term

What is the most likely cause of air leaks into a chiller refrigerant circuit?

Definition
Term

How is a purge unit connected on a low pressure chiller?

Definition

The inlet of the purge unit is typically connected to the top of the condenser.

Term

Where is the suction of a purge unit connected?

Definition

The inlet of the purge unit is typically connected to the top of the condenser.

Term

What is a high efficiency purge unit?

Definition

It removes non-condensables that contain a low percentage of refrigerant. This adds to the value of the purge drum in refrigerant containment.

Term

Shaft seals on an open type compressor are susceptible to what failures?

Definition
Term

Purge units work best when they are not needed. How can purge unit operating time be reduced?

Definition

By regular leak checking and repairing any leaks on a regular schedule.

Term

What is the maximum pressure that can be used when leak checking a low pressure chiller?

Definition

10 PSIG on low pressure equipment that utilizes a rupture disk.

Term

What is the preferred method of leak checking a charged low pressure chiller?

Definition

By increasing the refrigerant pressure using an external heat source or running hot water through the chiller tubes not to exceed 10 PSIG.

Term

Where should you check for leaks between a chiller refrigerant tube and the water box?

Definition

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.

Term

What is a hydrostatic tube test kit used for?

Definition

To check for leaks in a chiller tubes.

Term

What leak rate is permissible on industrial and process refrigeration?

Definition

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.

Term

What leak rate is permissible on equipment other than industrial and process equipment?

Definition

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.

Term

According to ASHRAE 3-1990, what rise is permitted in vacuum level during a standing vacuum test?

Definition

Starting at 1mm of Hg., after 12 hours the vacuum reading should not increase to more than 2.5 mm of Hg.

Term

List two steps to reduce the run time of a purge unit.

Definition

Regular leak checks and repair any leaks.

Term

Why should the water side of the evaporator and condenser be drained before recovering refrigerant from a chiller suspected of having tube leaks?

Definition

To prevent moisture form being drawn into the refrigerant circuit.

Term

If a purge unit is operating excessively, what problem can you expect to find?

Definition
Term

What condition would cause continuous excessive moisture collection in the purge unit of a low pressure refrigeration system?

Definition

Leaks between the refrigerant circuit and the water circuit.

Term

Why should oil be warmed prior to removal from a low pressure chiller?

Definition

To vaporize any liquid refrigerant that might be trapped in the oil.

Term

After liquid recovery, what must be done with the vapor still in the system?

Definition

Vapor recovery must be performed.

Term

Is recovery of refrigerant from a low pressure appliance typically started with liquid or vapor?

Definition

Start with liquid removal.

Term

Where is the connection made for the water supply used on a water cooled recovery unit?

Definition
Term

What should be the maximum pressure on the discharge of a recovery machine for low pressure systems?

Definition

10 PSIG, because the rupture disk is set to open at 15 PSIG.

Term

What should be done with the water pumps during a recovery form a low pressure chiller?

Definition
Term

What is EPA's definition of a "major repair"?

Definition

Any repair that involves the removal of the compressor, evaporator, condenser, or any auxiliary heat exchange coil.

Term

What recovery vacuum must be met on a low pressure appliance using a machine built in 1992?

Definition
Term

Why should you wait a few minutes after reaching the required recovery vacuum on an appliance to see if pressure rises?

Definition

To see if refrigerant is still trapped in the system.

Term

Under what circumstances may the recovery from an appliance be stopped without reaching the prescribed level?

Definition

If the recovery would contaminate the refrigerant being recovered. (this level cannot exceed 0 PSIG.)

Term

Is it a requirement that recycling and recovery equipment be capable of handling more than one refrigerant?

Definition
Term

Is it permissible to warm the refrigerant under EPA's regulations to pressurize a low pressure system to do a non-major repair?

Definition
Term

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?

Definition

25 inches of Hg, 25 mm of Hg. Absolute (equal to about 29 inches of Hg.)

Term

A vacuum pump that is too large for a particular system can cause what problem?

Definition

It can cause moisture to freeze in the system.

Term

How can you prevent moisture from freezing during dehydration?

Definition

You can raise the pressure with nitrogen and allow the ice to melt, then continue with the evacuation.

Term

Are multiple relief valves connected in series or parallel?

Definition
Term

ASHRAE Standard 15 covers refrigerant level monitoring for what refrigerants?

Definition
Term

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?

Definition

May not exceed the TLV-TWA. (Threshold limit value-Time weighted average.)

Term

List four safety procedures that should be followed when working with liquid low pressure refrigerant.

Definition
1. Use refrigerant sensors in equipment room.2. Avoid siphoning refrigerant by mouth. 3. Wear butyl-lined gloves.

4. Wear safety glasses.

Term

What is the toxicity and flammability rating of HCFC-123 per ASHRAE Standard 34?

Definition
Which factor does not affect the speed of evacuation? (2024)

FAQs

Which factor does not affect speed of evacuation? ›

The size of the equipment being evacuated.

What factors affect the speed of an evacuation? ›

What factors affect the speed of an evacuation? The size of the equipment, the ambient temperature, the suction line size, and the quantity of moisture in the system.

What does over evacuation of a system cause? ›

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.

What is for accurate readings during evacuation? ›

For the most accurate readings during evacuation, the vacuum gauge (Micron Gauge) should be located as far as possible from the vacuum pump. Measuring the vacuum of a system should be done with the system isolated and vacuum pump turned off.

What are the four factors that affect evacuation time? ›

What are the four factors that affect the evacuation time? Size of the equipment being evacuated, ambient temp, amount of moisture in the system, and size of vacuum pump and suction line.

What are the 3 ways of evacuation? ›

What are the 3 Categories of Fire Evacuation?
  • Simultaneous Evacuation.
  • Vertical or Horizontal Phased Evacuation.
  • Silent Alarm Evacuation.

What are 3 reasons for evacuation? ›

Reasons
  • Road accidents.
  • Train wreck.
  • Emergency aircraft evacuation.

What is the speed of an evacuation? ›

The distance between the observers were measured using a manual distance meter. The study found that the average walNing speed during the evacuation was 1.419 m/s.

What are the factors to be considered in an evacuation? ›

Whether or not you need to evacuate depends on several factors. These include the type of emergency and the characteristics of the building (e.g., how many stories, the construction material). Your plan should specify the exact conditions that require an evacuation of all office employees and staff.

Which of the following can affect the speed and efficiency of an evacuation? ›

Various factors can affect evacuation performance such as mode choices, minimum milling time, walking speed, maximum driving speed, car-following behavior, and critical tsu- nami inundation depth.

What are the five stages of evacuation? ›

responsibilities of applicable agencies, through the five stages of evacuation; decision, warning, withdrawal, shelter and return, and applies to Incident Controllers and agencies who are required to perform tasks in the event of an evacuation.

What is the risk of evacuation? ›

What are these risks? Evacuation poses issues. The most obvious are physical barriers like stairs and doors, and even cultural issues such as equality come into play. The hierarchy of employees in a business, for example, should be put to one side when an evacuation takes place.

What are the three 3 most important elements of an evacuation plan? ›

Conditions under which an evacuation would be necessary. Conditions under which it may be better to shelter-in-place. A clear chain of command and designation of the person in your business authorized to order an evacuation or shutdown. Specific evacuation procedures, including routes and exits.

What is the correct priority of evacuation? ›

In almost all cases, the top priority for evacuation is moving those who are in immediate danger. In case of fire, chemical spill, or other localized danger, identifying those at highest risk is easy because it is based on proximity.

What is the correct evacuation procedure? ›

As you approach the landing of each floor, allow evacuees from that level to enter the stairwell. Steer clear of hazards. If evacuation becomes difficult via a chosen route, because of smoke, flames or blockage, re-enter the facility on a safe floor. Continue evacuation via the nearest safe exit route.

What not to do during an evacuation? ›

During Evacuation:

(Do not open door if hot). Close the door as you exit your room or office. Dress appropriately for the weather. Take only essentials with you (e.g., eyeglasses, medications, identification and cash/checkbook/credit cards) - do not pack belongings.

What factors affect the decision of whether to evacuate the shelter in place? ›

The decision to evacuate or shelter-in-place (SIP) will be driven by the circumstances of a given chemical, biological or radiological emergency. IMMEDIATE concerns in the decision-making process are as follows: Evacuation-Potential for exposure to the people being evacuated.

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