10 - Equipment and Instruments for Refrigerant Handling and Service

Question 1

How do spring operated relief valves, rupture disks, and fusible plugs operate?

Answer 1

Spring-Operated relief valves open under excessive pressure, and then close again when enough refrigerant has been released from the cylinder to lower the pressure.

Rupture disks are designed to open under excessive pressure, but do not close again. They will release the entire charge into the atmosphere.

A fusible plug is made of a metal with a low melting point, which melts and releases a cylinder’s entire refrigerant charge if the cylinder begins to overheat.

Question 1

When should a refrigerant cylinder have a pressure release protective device, and what should they be?

Answer 1

Cylinders that have a diameter of 4 1/2” or greater and a length of 12” or more must have a pressure release protective device. This device can be a rupture disc, a fusible plug, or a spring-operated relief valve. These are designed to allow refrigerant to escape from a cylinder when the pressure or temperature is too high.

Question 2

Who prescribes the regulations for refrigerant cylinders?

Answer 2

The Department of Transportation (DOT)

Question 3

How often should cylinders be inspected and re-certified?

Answer 3

Cylinders with a corrosive refrigerant must be inspected and recertified every five years. Cylinders with non-corrosive refrigerants, every ten years.

Question 4

What are the three main types of refrigerant cylinders?

Answer 4

Storage cylinders, disposable cylinders, and recovery cylinders.

Question 5

What is a storage cylinder?

Answer 5

Large storage cylinders are used to charge refillable service cylinders at the shop. Often, the storage cylinders are positioned upside down with the valve at the bottom to make filling a service cylinder easier and faster.

Question 6

What is a disposable cylinder?

Answer 6

Disposable service cylinders are one of the most commonly used types of refrigerant container. They are designed for one use only. They are used to charge refrigerants into a system. They should be stored at temperatures below 125 to prevent refrigerant pressure buildup. They can be used to charge with vapor (valve side up) or liquid (valve side down).

Question 7

How should disposable cylinders be disposed of?

Answer 7

All refrigerant must be recovered into an approved recovery cylinder. The cylinder must be evacuated down to atmospheric pressure. The cylinder may then be disposed of or recycled. Many refrigerant supply stores offer recycling of used disposable cylinders.

Question 8

What are Recovery cylinders?

Answer 8

Recovery cylinders are refrigerant cylinders specifically dedicated to storing refrigerant recovered refrigeration systems. Each cylinder is dedicated to only one type of refrigerant. These cylinders are easily recognized by their gray paint on the lower portion and yellow paint on the upper portion.

Question 9

How often should a recovery cylinder be tested.

Answer 9

Over 300 psig, every five years. Under 300 psig, every ten years.

Question 10

What are pressure gauges?

Answer 10

Pressure gauges are instruments that measure and display the pressure of a fluid in a container.

Question 11

What is a bourdon tube?

Answer 11

A bourdon tube is a thin walled tube of elastic metal bent into a circular shape that straightens as pressure inside it increases. One end of a bourdon tube is sealed closed, while the other end is connected to a fitting that connects into a valve on a refrigeration system. With the sealed end connected to a linkage and a specially engineered gear with an indicator needle, a bourdon tube’s reaction to pressure indicates pressure on a given scale.

Question 12

What is a retarder?

Answer 12

A retarder allows a gauge to measure pressure readings at higher pressures . After the pressure has crossed a certain pressure threshold, a retarder engages an extra spring that correlates with the gauge’s higher graduation markings.

Question 13

What are the three main types of pressure gauges used in HVACR service work?

Answer 13

1 - Vacuum gauges (30” hg vacuum through 0” hg vacuum)
2 - Compound gauges (30” hg vacuum through 240 psi)
3 - High-pressure gauges (0 psi through 800 psi)

Question 14

What is a vacuum gauge?

Answer 14

A vacuum gauges measures lower than atmospheric pressure.

Question 15

What is a micron?

Answer 15

A micron is the equivalent of 0.001 mm hg.

Question 16

What is the difference in vacuum measurement between microns and in hg?

Answer 16

A deeper vacuum measured in microns will correspond to a decreasing value of microns. A perfect value measured in microns is 0, with the value increasing as pressure is added. Vacuum measurements in hg in will increase once pressure decreases past atmospheric pressure (29.92 in hg) from 0 in hg vacuum, until a perfect vacuum is reached at 29.92 in hg vacuum. (in hg and in hg vacuum are inverse one pressure deceases past atmospheric pressure)

Question 17

How is a vacuum used to remove water from the inside of a refrigeration circuit?

Answer 17

A vacuum of 250 microns will decrease the pressure enough to cause liquid water to evaporate and be drawn out of the system. To measure such a low pressure, a vacuum gauge must be used, as a compound gauge will not be able to accurately measure a deep vacuum.

Question 18

How can a technician determine if water is present inside a system?

Answer 18

If a vacuum is drawn out of the system and the vacuum levels off at 5000 microns, ice or water is in the system.

Question 19

How can a thermistor vacuum gauge be cleaned?

Answer 19

1. Fill the tube with cleaning solvent using a eyedropper.
2. Rock the tube gently, and empty it when finished
3. Repeat steps 1-2 two or three times.
4. Clean with an alcohol rinse.
5. Clean the instrument dial cover with soap, water, and facial tissues.

Question 20

What is a compound gauge

Answer 20

A compound gauge measures pressure above atmospheric and also vacuum. It is also known as a low-side gauge. It is compound because it measures both above and below atmospheric pressure.

Question 21

What is a high pressure gauge?

Answer 21

A high pressure gauge is a pressure gauge that can read high pressure values on a single continuous scale.

Question 22

How can a gauge be calibrated?

Answer 22

Disconnect the gauge so that it is open to the air. Set the indicator needle to 0.

Question 23

What is the difference between psi, psia, and psig?

Answer 23

PSI is the most basic form of measurement. It stands for pressure per square inch. Most pressure transducers are measured in psi.

PSIA is absolute pressure, and scales up from a perfect vacuum.

PSIG is relative to atmospheric pressure, and will increase from there. Any decrease will be measured in psig vacuum or psiv.

Question 24

What is a service valve?

Answer 24

A service valve is a valve with a wrench operated movable valve stem that blocks or opens passage trough the valve. The service valve also blocks or opens a service port, which provides a connection to the refrigeration system for taking pressure readings and adding or removing refrigerant or lubricant. Service valves enable technicians to seal off parts of the system while installing gauges or recharging or evacuating the system.

Question 25

What are the four different valve positions?

Answer 25

Back seated, front seated, mid position, and cracked open.

Question 26

What is the function of a back seated service valve?

Answer 26

If the valve stem is turned counterclockwise (outward) as far as possible, the valve is back seated. This closes off its service port from the rest of the system, so no pressure readings or procedures can be performed. This is used for normal system operation.

Question 27

What is the function of a front seated service valve?

Answer 27

If the valve stem is turned clockwise (inward) as far as possible, the valve is front seated. When a service valve is front seated, it blocks the flow of refrigerant through the valve by closing off it’s regular passageway. Front seating a service valve provides a passage between part of the refrigeration system and the service port.

Question 28

What is the function of a mid position service valve?

Answer 28

When the valve stem is turned so that the valve is not against either seat but midway between the front and back, the service valve is in mid-position. This is usually done by beginning with the valve in the back-seated position and turning the valve stem two complete clockwise rotations. This position accomplishes two objectives: it allows refrigerant to continue flowing, and it provides a connection between the rest of the system and the service port.

Question 29

What is the function of a cracked open service valve?

Answer 29

A service valve is cracked open when the valve stem has been turned just enough to lift the valve off the back seated position. This allows refrigerant to continue flowing while providing a connection between the rest of the system and the service port.

Question 30

What is a suction line service valve?

Answer 30

This is a low side service valve connected to a refrigeration system’s suction line. In many cases, a suction line service valve is located much closer to the compressor’s inlet than to the evaporator. These are often found on the condensing unit of a split system. During normal system operation, cool low-pressure vapor refrigerant flows through this valve.

Question 31

What is a suction service valve? (SSV)

Answer 31

This is a low side service valve that connects to the suction line and directly onto the compressor at its inlet. Valve caps protect the service port and valve stem when the valve is not in use. It is considered a compressor service valve because it is one of the two service valves connected directly onto the compressor.

Question 32

What is a discharge service valve? (DSV)

Answer 32

This is a high side service valve that is mounted at a compressor’s discharge port, providing a shutoff between the compressor and the condenser. It also provides a service port for a high pressure gauge or a gauge manifold. During normal operation, hot, high pressure refrigerant vapor flows through this valve. This valve is considered a compressor service valve.

Question 33

What is a liquid line service valve?

Answer 33

This is a high side service valve located in a refrigeration system’s condenser and liquid line. In many cases, a liquid line service valve is located much closer to the condenser’s outlet than to the metering device. These service valves are often found on the condensing unit of a split system. During normal system operation, warm high

Question 34

What is a liquid receiver service valve? (LRSV)

Answer 34

A liquid receiver service valve, or queen valve, is a high side service valve connected to the outlet of a liquid receiver and the inlet of a liquid line. These valves enable the technician to charge liquid refrigerant into the system.

Question 35

Where is the queen valve, and what is it useful for?

Answer 35

The queen valve is installed between the condenser and the liquid receiver inlet. King and queen valves are useful when pumping down systems for component isolation.

Question 36

What is valve packing?

Answer 36

Valve packing is a string sealant that creates a pressure seal between the inside and outside of a valve, preventing fluid from leaking out. It’s made up of rings of resilient or semi-resilient material that are placed around the valve’s stem or shaft and push against it and the valve body to create the seal.

Question 37

What is a valve gland?

Answer 37

A valve gland is a mechanical seal that compresses packing material around a valve stem or shaft to create a barrier that prevents fluids or gases from escaping. This compression creates a leak-free seal that allows machinery to operate smoothly and efficiently.

Question 38

What is a valve stem?

Answer 38

A valve stem is a self-contained valve that opens to admit gas to a chamber, and is then automatically closed and kept sealed by the pressure in the chamber, or a spring, or both, to prevent the gas from escaping.

Question 39

What are the four key points to keeping a service valve in good working order?

Answer 39

1. Keep the valve body free of moisture to prevent rusting on the stem
2. Match the correct service valve wrench size to the valve stem to prevent stripping of the valve stem head.
3. Maintain the packing so that the service valve will not leak: occasionally tighten the packing head
4. Oil and seal the threads of the service port each time gauges are used and caps are replaced.

Question 40

How can risk be minimized when opening a stuck service valve?

Answer 40

Always use a fixed wrench rather than a ratchet wrench. This is done so the valve can be quickly closed again if a leak or breakage occurs.

Question 41

How can a technician avoid valve stem freezing?

Answer 41

After back seating a valve, turn it just enough to relieve some of the pressure on the seat, but not enough to open the valve. This provides just enough clearance between the valve and it’s seat to prevent it form getting jammed into its seat if the valve body contracts.

Question 42

How can a stuck service port plug be loosened?

Answer 42

Heat the outside of the service valve body with a flame from a torch. Be careful not to overheat it, it should not glow. After the threads are loosened, use a wrench to gently turn and loosen the plug.

Question 43

What is an access port?

Answer 43

An access port is a small valve opening that usually contains a schrader valve core and is used for checking pressure and servicing a system.

Question 44

What is a bypass valve?

Answer 44

Discharge Bypass Valve is used to bypass a portion of the hot discharge gas directly into the low side to limit the minimum evaporating pressure during periods of low load either to prevent coil icing or to avoid operating the compressor at a lower suction pressure than it was designed to operate.

Question 45

What is a hot gas defrost valve?

Answer 45

In hot gas defrost, refrigerant vapor from either the compressor discharge or the high pressure receiver is used to warm the evaporator coil and melt the frost that has collected there. The vapor condenses to a liquid during this process, and is then routed back to a protected suction line or to an accumulator. It’s often used in commercial appliances like ice machines and freezers.

Question 46

What is a schrader valve?

Answer 46

A schrader valve consists of an externally threaded, hollow tube with a spring loaded, coaxially centered pin that blocks access through the tube. The tube can be opened by depressing the pin against the spring pressure.

Question 47

What are schrader valve cores?

Answer 47

Having external threads allows schrader valves to be used as valve cores inside access ports. This allows a valve core to be removed from an access port for certain procedures, such as pulling a vacuum.

Question 48

What are piercing valves?

Answer 48

The most common method used to gain access to small hermetic systems or those without access ports is to use piercing valves. A piercing valve is a valve that is secured to a length of tubing and accesses the refrigeration system by piercing through the tubing

Question 49

What are the pros and cons between a bolted on and brazed on connection?

Answer 49

Bolted on piercing valves do not require refrigerant removal prior to installation, but their seal may leak over time in systems with large vibrations. They should be used as temporary access to the system.

Brazed on piercing valves seldom leak, but they do require refrigerant removal prior to brazing.

Question 50

What are the three criteria that must be followed when selecting a bolt on piercing valve?

Answer 50

1. The rubber or nylon seal should be clean
2. The tubing should be straight and clean
3. The correct diameter valve must be selected for the correct diameter tubing

Question 51

What is the nine step procedure to installing a bolted on piercing valve?

Answer 51

1. Assess the location where the valve will be installed: Make sure there is enough space around the tubing to operate and install the valve, make sure hoses can be easily attached.
2. Make sure the part of the tubing you intend to install the valve on is straight, round, and free of any dents or irregularities
3. Clean the area with a fine emery cloth or fine sandpaper. Be careful to not scratch the tubing while cleaning. Wipe it clean when done with a clean cloth to remove any dust.
4. Back out the valve’s piercing needle as far as it will go
5. Dab a little nylog on the tubing.
6. While holding the sealing washer steady to be sure it stays in place, mount the valve on the tubing. Secure the valve body too the tubing by tightening the screws evenly and snugly.
7. Once the valve body is firmly clamped to the tubing, attach the service hose and rotate the piercing valve stem clockwise into the tubing. It will become easier to tighten when the needle pierces the tubing
8. Back off the piercing needle slightly in order to access the system
9. Test for leaks to make sure the seal is airtight between the piercing valve and tubing.

Question 52

What is the eleven step procedure to installing a brazed on piercing valve?

Answer 52

1. With the size of the piercing valve in mind, check to see if there is enough space around the tubing to install and operate the piercing valve. Also make sure there will be enough room to attach service hoses.
2. Ensure the area of tubing you intend to install the valve on is straight, round, and without any dents or irregularities.
3. Clean both the saddle and tubing mating surface with clean sandpaper or clean steel wool. Wipe both the saddle and the tubing with a clean cloth to remove any dust.
4. Remove the piercing valve stem and the gasket from the saddle.
5. Brazing requires flux or flux-coated filler rod. If using a flux-coated filler rod, mount the saddle on the tubing. If not using a flux-coated filer rod, apply clean, fresh brazing flux on the saddle according to the valve manufacturer’s directions. Then mount the saddle on the tubing. To prevent the saddle from moving during the brazing process, a small c clamp can be used to secure it in place.
6. Check to see if there is enough room for using the valve in its present location. If there is not, find a more suitable location with better clearance.
7. Using a torch, heat both the tubing and saddle until the filler rod material flows around the saddle. Do not overheat the tubing or it may be weakened to the point of failure and burst. (note: ensure nitrogen is flowing during the brazing process to prevent porosity in the weld)
8. When you have finished brazing the joint, inspect it carefully. Use a mirror to check hard to see edges
9. After the brazed joint has cooled, install the piercing needle and gasket. Many piercing valve caps have O-rings. These seal the system. O-rings must be in place before installing the cap to ensure a proper seal. Caps with a metal-to-metal seal must be tightened one-eighth of a turn with a wrench after being finger tightened. Can be sealed additionally with Nylog.
10. Attach the service hose and then back off the piercing valve stem slightly to access the system.
11. Test for leaks to make sure the seal between the piercing valve and tubing is airtight.

Question 53

What is a gauge manifold?

What is it used for?

Answer 53

A gauge manifold consists of a compound (low-side) gauge, a high-pressure (high side) gauge, and at least three ports that may be isolated form each other, and at least two hand valves.

A gauge manifold allows a service technician to check the operating pressures of both the low side and high side simultaneously, to add or recover refrigerant, to add oil, to bypass the compressor, and to perform many other service operations.

Question 54

What is the 6 step process to purging a gauge manifold and hoses?

Answer 54

1. Before beginning, make sure all gauge manifold valves and system service valves are closed.
2. Connect the center service line to a refrigerant cylinder containing the same refrigerant used in the system.
3. Remove the service caps from the systems access ports, and loosely connect the gauge manifold’s lines for purging.
4. Open the low and high side valves on the gauge manifold.
5. Briefly crack open the cylinder valve on the refrigerant tank to flush the gauge manifold and service lines with refrigerant. Any moisture or air will be forced out of the loose connections at the service ports.
6. Close the cylinder valve and tighten the service line fittings at the access ports.

Question 55

What are the six different methods of leak detection?

Answer 55

1. Bubble Solutions
2. Fluorescent Dyes
3. Refrigerant Dyes
4. Halide Torches
5. Electronic Detectors
6. Ultrasonic Detectors

Question 56

What are some tips to remember when conducting a leak search?

Answer 56

1. Check connections: Tubing connections and brazed areas, especially high stress/vibrations such as near a compressor
2. Look for Oily or Dusty areas

Question 57

What is the EPA Leak Repair Standard for Commercial/Industrial refrigeration and comfort cooling?

Answer 57

If a system contains more than 50 lbs of refrigerant and has yearly leak rates at or above trigger levels, a repair is required within 30 days. (35% for commercial and industrial equipment, 15% for comfort cooling and other appliances) These requirements do not apply to systems containing 50 lbs or lower.

Question 58

How does the bubble solution leak detection method work?

What are its pros and cons?

What is an important quality tip to remember when using bubble solution?

Answer 58

It is a soap-water or solution that is brushed/sprayed over an area of tubing. If there is a leak, bubbles with form. It is useful for pinpointing the exact location of a leak

A bubble solution is low-cost and easy. It will also not react to the refrigerant used in Urethan insulation. However, a large high pressure leak can blow through the solution and no bubbles will appear.

(Note: wipe bubble solution off of ACR tubing when finished to avoid oxidization. When using soap bubbles or refrigerant dye, operate the system prior to leak detection to build pressure.)

Question 59

How does the Refrigerant/Fluorescent Dye detection method work?

What are its pros and cons?

What is an important tip to remember?

Answer 59

It involves charging a dye into a refrigeration system and observing areas suspected of leaks during operation. Most leaks will show after a short time, however it may take longer (24 hours) to indicate leaks, especially if it is very small. Fluorescent dyes show up under ultraviolet light.

The biggest advantage of fluorescent dye is that there are no false alarms, if you see the dye, there is a leak. Unfortunately, wind and bright sunlight can make detecting small leaks hard. Excessive use of dyes can also reduce a refrigerant’s cooling capacity, lower lubricant viscosity, and even damage internal components in high concentrations.

(Note: always use dye that is compatible with the refrigerant in the system. Also, block out bright lights when using color changing methods)

Question 60

How does the Halide Torch detection method work?

\What are its pros and cons?

Answer 60

Halide torches burn a flammable gas over a copper strip, while supplying the flame with oxygen through a siphon hose. When most gases burn with a copper strip placed inside the flame, it will turn green in the presence of the tiniest amount of halogenated refrigerant. (All CFC, HFC, and HCFC refrigerants contain halogen) If the flame turns green, a refrigerant leak is near the inlet of the rubber hose.

Halide torches are no longer commonly used. They can be difficult to use in the presence of wind or bright sunlight, and will throw a false reading when used near urethane insulation, as it contains some refrigerant chemicals as an expander. It can however be used to success when combined with a bubble solution to pinpoint the exact location.

Question 61

How does the Electronic Leak detection method work?

\What are its pros and cons?

Answer 61

They use electronic sensors to determine if a refrigerant is present. They are often able to detect very small leaks. The detector is first dialed in to atmospheric pressure, then a probe is passed over surfaces suspected of leaking. A small pump draws air into the unit through the probe, and if a small amount of refrigerant is detected, the detector will emit a flash and audio cue.

ELDs can be thrown off by drafts. Shut off any fans that cause air movement. The tip can become contaminated by water or other substances, and this will interfere with its operation. A plastic guard tip should be used in these situations. They should also not be used near areas containing explosive or flammable vapors. ELDs will also throw a false reading when used in the presence of urethane insulation.

Always position the sniffer below the suspected leak, since refrigerant is heavier than air. Move the tip slowly at a rate of about one inch per second.

Question 62

How does the ultrasonic leak detection method work?

\What are its pros and cons?

Answer 62

These detect the sound that a vapor makes as it is escaping from a pressurized system.

It is compatible with all refrigerants. However, background noise produced by equipment not related to the system can sometimes produce false alarms. Turn off any noise producing equipment when operating an ultrasonic detector

Question 63

What is a vacuum pump?

Answer 63

It is a vapor pump used to create vacuums for evacuating a refrigerant system of moisture and other contaminants before refrigerant is recharged into the system.

Question 64

How many microns due manufacturers usually recommend a system be vacuumed down to before charging?

Answer 64

500 microns.

Question 65

What is ultimate vacuum?

Answer 65

Ultimate vacuum is the highest vacuum that a vacuum pump can pull. It is the most important specification of a vacuum pump and is usually measured in microns.

Question 66

What is free air displacement? What is it measured in, and what is an alternative name for it?

What are the recommended pump capacities for residential, medium, and large systems?

Answer 66

It is the speed at which gas may be pumped through a vacuum pump. It is measured in CFM. It may also be known as volume capacity.

1.5 cfm - 3 to 5 ton residential systems
3-5 cfm - 5 to 100 ton medium systems
10-15 cfm - large systems over 100 tons

Question 67

What are the two main types of vacuum pumps?

What are the applications of both?

Answer 67

Single stage and multi stage

Single stage uses a single pump mechanism to draw a vacuum. These can only be used when the triple evacuation method is used.

Two stage vacuum pumps consist of two pump mechanisms working in series. Working together, they are able to draw a vacuum more efficiently than a single pump mechanism. These are used when the deep vacuum method is used.

Question 68

What is the purpose of oil in a vacuum pump?

How does pump oil interact with system contaminants?

Answer 68

It is used as a lubricant for the pump and as a fluid seal between air, gases, and contaminants entering the pump from the refrigeration system.

During evacuations, gases and water vapor pulled from the system often become trapped in the oil, which raises the oil level in the pump. Oil should be replaced frequently since oil rapidly becomes dirty when water and solvent vapor are drawn and dissolved into it.

Question 69

What can dirty oil do to a vacuum pump? How can you tell if the oil is dirty?

Answer 69

Water will turn the oil white and foamy. If contaminated oil is left in the pump, sludge will form, reducing the service life of the pump. If pump oil is clear, it means it is clean. Dirty oil also reduces a pump’s ultimate vacuum.

Question 70

What is the 7 step process to testing a vacuum pump?

Answer 70

1. Using a tee fitting, connect an electronic vacuum gauge between the vacuum pump and the center port of a gauge manifold.
2. Close the low and high side gauge manifold valves.
3. Start the vacuum pump.
4. Allow the pump to run long enough to pull a vacuum of approximately 500 microns.
5. Turn off the pump and wait two to three minutes, allowing the pressure to rise as moisture boils off inside the hose.
6. Pull another vacuum down to 500 microns.
7. Watch the vacuum gauge reading. If it rises, check for leaks at the hose fittings. If a pump will not pull down to high vacuum, change the oil.

Question 71

What does the term recovering mean?

Answer 71

This refers to removing refrigerant from a system and storing it in an external container, regardless of the condition of the removed refrigerant. Recovered refrigerant is usually returned to to system from which it was taken following repairs.

Question 72

What does the term recycling mean?

Where is it typically performed?

Answer 72

It refers to cleaning a refrigerant for reuse by separating out the oil and passing the refrigerant through filter driers. It can be returned to the system it was recycled from, or put into another system operated by the same owner.

It is usually done at a jobsite or a local service shop.

Question 73

What must be done to a refrigerant before it can be resold?

Answer 73

It must be reclaimed.

Question 74

What does the term reclaiming refer to?

What are the requirements for reclamation? What regulation does this fall under?

Answer 74

It refers to processing a recovered refrigerant so that it is chemically pure.

The reprocessed refrigerant must be analyzed at an approved testing facility before it can be classified as being reclaimed. It must meet the AHRI Standard 700 for purity.

Question 75

What procedures must be followed in the event of a refrigeration system repair?

Answer 75

Before any repairs can take place, all refrigerant in the system must be recovered. After repairs are finished, the system must be then be evacuated to remove all moisture and contaminants before recharging.

Question 76

What act prohibits the venting of refrigerants?

Answer 76

Section 608 of the clean air act.

Question 77

What is the primary purpose of a recovery machine?

Answer 77

To remove refrigerant from a system.

Question 78

What is the cutoff age for recover machines required by the EPA to be certified?

Answer 78

November 15, 1993.

Question 79

What are seven maintenance tasks to perform on a recovery machine?

Answer 79

1. Change the filter drier per the mfg schedule.
2. Perform leak checks, the fittings for connections may loosen with use. (every 3 months)
3. Verify overfill or high-pressure shutoff.
4. Check gauge calibration. Use a reference gauge and compare its readings against the recovery machine’s gauge.
5. Check the recovery machine’s compressor oil. In general, compressor oil should not need to be changed or added. However, in the event of a compressor slug, the oil may be washed out. This does not apply to oil-less compressors.
6. Complete a visual inspection. Check hoses, fittings, tank expiration, lights and electronic indicators, and clean the case/control panel.
7. Use appropriate cables. Use short, heavy duty extension cables rated to handle the equipment’s amp draw.

Question 80

How frequently should a recovery tank be certified?

Answer 80

Every five or ten years.

Question 81

What is a digital charging scale?

What is Tare weight?

Answer 81

I is an electronic refrigerant scale that monitors the weight of a refrigerant cylinder as refrigerant is being charged into or recovered from a system.

Tare weight is the weight of the recovery cylinder when it is empty.