Air Conditioning Clinic Manual
CLICK ANYWHERE on THIS PAGE to RETURN to REFRIGERANT PIPING Information at InspectApedia.com Air Conditioning Clinic Refrigerant Piping One of the Fundamental Series June 2011 TRG-TRC006-EN
Refrigerant Piping One of the Fundamental Series A publication of Trane
Preface Refrigerant Piping A Trane Air Conditioning Clinic Figure 1 Trane believes that it is incumbent on manufacturers to serve the industry by regularly disseminating information gathered through laboratory research, testing programs, and field experience. The Trane Air Conditioning Clinic series is one means of knowledge sharing. It is intended to acquaint a technical audience with various fundamental aspects of heating, ventilating, and air conditioning (HVAC). We have taken special care to make the clinic as uncommercial and straightforward as possible. Illustrations of Trane products only appear in cases where they help convey the message contained in the accompanying text. This particular clinic introduces the reader to refrigerant piping. 2011 Trane ii All rights reserved TRG-TRC006-EN
Contents period one Refrigerant Piping Requirements . 1 period two Suction Line . 10 Requirements for Sizing and Routing . 10 Sizing Process . 12 Other Considerations . 24 period three Discharge Line . 31 Requirements for Sizing and Routing . 31 Sizing Process . 33 Other Considerations . 39 period four Liquid Line . 41 Requirements for Sizing and Routing . 41 Sizing Process . 45 Other Considerations . 57 period five Hot-Gas Bypass Line . 60 Hot-Gas Bypass to Evaporator Inlet . 62 Hot-Gas Bypass to the Suction Line . 66 Other Considerations . 68 period six Review . 70 Quiz . 76 Answers . 78 Glossary . 79 TRG-TRC006-EN iii
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period one Refrigerant Piping Requirements notes Refrigerant Piping period one Refrigerant Piping Requirements Figure 2 The focus of this clinic is on the design and installation of the interconnecting piping for vapor-compression refrigeration systems. Reviewing the physical changes that the refrigerant undergoes within the refrigeration cycle will help demonstrate certain demands that the piping design must meet. This clinic focuses on systems that use Refrigerant-22 (R-22). While the general requirements are the same for systems that use other refrigerants, velocities and pressure drops will differ. Vapor-Compression Refrigeration condenser D C expansion device compressor B A evaporator Figure 3 Figure 3 illustrates a basic vapor-compression refrigeration cycle. Refrigerant enters the evaporator in the form of a cool, low-pressure mixture of liquid and vapor (A). Heat is transferred to the refrigerant from the relatively warm air that is being cooled, causing the liquid refrigerant to boil. The resulting refrigerant vapor (B) is then pumped from the evaporator by the compressor, which increases the pressure and temperature of the vapor. TRG-TRC006-EN 1
period one Refrigerant Piping Requirements notes The resulting hot, high-pressure refrigerant vapor (C) enters the condenser where heat is transferred to ambient air, which is at a lower temperature than the refrigerant. Inside the condenser, the refrigerant vapor condenses into a liquid and is subcooled. This liquid refrigerant (D) then flows from the condenser to the expansion device. This device creates a pressure drop that reduces the pressure of the refrigerant to that of the evaporator. At this low pressure, a small portion of the refrigerant boils (or flashes), cooling the remaining liquid refrigerant to the desired evaporator temperature. The cool mixture of liquid and vapor refrigerant (A) enters the evaporator to repeat the cycle. The vapor-compression refrigeration cycle, and the four major components of the refrigeration system (evaporator, compressor, condenser, and expansion device), are discussed in more detail in separate clinics. Refer to the list of references at the end of Period Six. Interconnecting Refrigerant Piping C discharge line condenser liquid line expansion device compressor B A suction line D evaporator Figure 4 These individual components are connected by refrigerant piping. The suction line connects the evaporator to the compressor, the discharge line connects the compressor to the condenser, and the liquid line connects the condenser to the expansion device. The expansion device is typically located at the end of the liquid line, at the inlet to the evaporator. There is more to the design of refrigerant piping than moving refrigerant from one component to another. Regardless of the care exercised in selection and application of the components of the refrigeration system, operational problems may be encountered if the interconnecting piping is improperly designed or installed. 2 TRG-TRC006-EN
period one Refrigerant Piping Requirements notes Refrigerant Piping Requirements V Return oil to compressor V Ensure that only liquid refrigerant enters the expansion device V Minimize system capacity loss V Minimize refrigerant charge Figure 5 When a refrigeration system includes field-assembled refrigerant piping to connect two or more of the components, the primary design goals are generally to maximize system reliability and minimize installed cost. To accomplish these two goals, the design of the interconnecting refrigerant piping must meet the following requirements: Return oil to the compressor at the proper rate, at all operating conditions Ensure that only liquid refrigerant (no vapor) enters the expansion device Minimize system capacity loss that is caused by pressure drop through the piping and accessories Minimize the total refrigerant charge in the system to improve reliability and minimize installed cost Scroll Compressor stationary scroll seal discharge discharge port intake driven scroll motor shaft intake Figure 6 The first requirement is to ensure that oil is returned to the compressor at all TRG-TRC006-EN 3
period one Refrigerant Piping Requirements notes operating conditions. Oil is used to lubricate and seal the moving parts of a compressor. For example, the scroll compressor shown in Figure 6 on page 3 uses two scroll configurations, mated face-to-face, to compress the refrigerant vapor. The tips of these scrolls are fitted with seals that, along with a thin layer of oil, prevent the compressed refrigerant vapor from escaping through the mating surfaces. Similarly, other types of compressors also rely on oil for lubrication and for providing a seal when compressing the refrigerant vapor. Characteristically, some of this lubricating oil is pumped along with the refrigerant throughout the rest of the system. While this oil has no function anywhere else in the system, the refrigerant piping must be designed and installed so that this oil returns to the compressor at the proper rate, at all operating conditions. Return Oil to Compressors discharge line liquid line warm liquid hot vapor condenser expansion device compressor evaporator suction line cool vapor Figure 7 Returning to the system schematic, droplets of oil are pumped out of the compressor along with the hot, high-pressure refrigerant vapor. The velocity of the refrigerant inside the discharge line must be high enough to carry the small oil droplets through the pipe to the condenser. Inside the condenser, the refrigerant vapor condenses into a liquid. Liquid refrigerant and oil have an affinity for each other, so the oil easily moves along with the liquid refrigerant. From the condenser, this mixture of liquid refrigerant and oil flows through the liquid line to the expansion device. Next, the refrigerant–oil mixture is metered through the expansion device into the evaporator, where the liquid refrigerant absorbs heat and vaporizes. Again, the velocity of the refrigerant vapor inside the suction line must be high enough to carry the droplets of oil through the pipe back to the compressor. Without adequate velocity and proper pipe installation, oil may be trapped out in the system. If this condition is severe enough, the reduced oil level in the compressor could cause lubrication problems and, potentially, mechanical failure. 4 TRG-TRC006-EN
period one Refrigerant Piping Requirements notes Thermostatic Expansion Valve (TXV) distributor TXV evaporator remote bulb liquid refrigerant external equalizer refrigerant vapor Figure 8 The second requirement of the refrigerant piping design is to ensure that only liquid refrigerant enters the expansion device. There are several types of expansion devices, including expansion valves (thermostatic or electronic), capillary tubes, and orifices. In addition to maintaining the pressure difference between the high-pressure (condenser) and low-pressure (evaporator) sides of the system, a thermostatic expansion valve (TXV) also controls the quantity of liquid refrigerant that enters the evaporator. This ensures that the refrigerant will be completely vaporized within the evaporator, and maintains the proper amount of superheat in the system. Subcooling subcooling pressure expansion device B { A C condenser mixture of liquid and vapor saturated vapor curve compressor evaporator saturated liquid curve enthalpy Figure 9 Inside the condenser, after all of the refrigerant vapor has condensed into liquid, the refrigerant is subcooled to further lower its temperature. This subcooled liquid refrigerant leaves the condenser (A) and experiences a pressure drop as it flows through the liquid line and accessories, such as a filter TRG-TRC006-EN 5
period one Refrigerant Piping Requirements notes drier and solenoid valve, installed upstream of the TXV. On the pressureenthalpy chart, Figure 9 on page 5, this moves the condition of the refrigerant toward the saturated liquid curve (B). If this pressure drop is high enough, or if the refrigerant has not been subcooled enough by the condenser, a small portion of the refrigerant may boil (or flash), resulting in a mixture of liquid and vapor (C) entering the expansion device. The presence of refrigerant vapor upstream of the expansion device is very undesirable. Bubbles of vapor displace liquid in the port of the TXV, reducing the flow rate of liquid through the valve, therefore substantially reducing the capacity of the evaporator. This results in erratic valve operation. The design of the piping system must ensure that only liquid refrigerant (no vapor) enters the expansion device. This requires that the condenser provide adequate subcooling at all system operating conditions, and that the pressure drop through the liquid line and accessories not be high enough to cause flashing. Subcooling allows the liquid refrigerant to experience some pressure drop as it flows through the liquid line, without the risk of flashing. Pressure Drop in a Suction Line impact on system performance, % 100 98 efficiency 96 capacity 94 92 R -22 R-22 90 2 (13.8) 4 (27.6) 6 (41.4) 8 (55.2) pressure drop, psi (kPa) (kPa) kPa) 10 (69.0) 12 (82.7) Figure 10 The third requirement of the refrigerant piping design is to minimize system capacity loss. To achieve the maximum capacity from the system, the refrigerant must circulate through the system as efficiently as possible. This involves minimizing any pressure drop through the piping and other system components. Whenever a fluid flows inside a pipe, a characteristic pressure drop is experienced. Pressure drop is caused by friction between the moving liquid (or vapor) and the inner walls of the pipe. The total pressure drop depends on the pipe diameter and length, the number and type of fittings and accessories installed in the line, and the mass flow rate, density, and viscosity of the refrigerant. As an example, the chart in Figure 10 demonstrates the impact of pressure drop, through the suction line, on the capacity and efficiency of the system. For this example system operating with Refrigerant-22, increasing the total 6 TRG-TRC006-EN
period one Refrigerant Piping Requirements notes pressure drop in the suction line from 3 psi (20.7 kPa) to 6 psi (41.4 kPa) decreases system capacity by about 2.5 percent and decreases system efficiency by about 2 percent. This reveals a compromise that the system designer must deal with. The diameter of the suction line must be small enough that the resulting refrigerant velocity is sufficiently high to carry oil droplets through the pipe. However, the pipe diameter must not be so small that it creates an excessive pressure drop, reducing system capacity too much. Minimize Refrigerant Charge filter drier evaporator liquid line suction line compressor discharge line condenser Figure 11 The first three requirements have remained unchanged for many years. However, years of observation and troubleshooting has revealed that the lower the system refrigerant charge, the more reliably the system performs. Therefore, a fourth requirement has been added for the design of refrigerant piping: minimize the total amount of refrigerant in the system. To begin with, this involves laying out the shortest, simplest, and most-direct pipe routing. It also involves using the smallest pipe diameter possible, particularly for the liquid line because, of the three lines, it impacts refrigerant charge the most. The chart in Figure 11 shows that the liquid line is second only to the condenser in the amount of refrigerant it contains. This reveals another compromise for the system designer. The diameter of the liquid line must be as small as possible to minimize the total refrigerant charge. However, the pipe diameter cannot be small enough to create an excessive pressure drop that results in flashing before the liquid refrigerant reaches the expansion device. TRG-TRC006-EN 7
period one Refrigerant Piping Requirements notes Involve the Manufacturer V If provided, use refrigerant line sizes recommended by manufacturer Figure 12 This clinic discusses the processes for sizing the interconnecting piping in an air-conditioning system. Some of the information required for selecting the optimal line sizes is best known by the manufacturer. Therefore, if the manufacturer of the refrigeration equipment provides recommended line sizes, or tools for selecting the optimal line sizes, we recommend that you use those line sizes. If, however, line sizes are not provided by the manufacturer, the processes outlined within this clinic could be used for selecting the sizes. General Piping Requirements V Use clean Type L copper tubing X Copper-to-copper joints: BCuP-6 without flux X Copper-to-steel (or brass) joints: BAg-28, non-acid flux V Properly support piping to account for expansion, vibration, and weight V Avoid installing piping underground V Test entire refrigerant circuit for leaks Figure 13 Before discussing the design and installation of the suction, discharge, and liquid lines, there are some general requirements that apply to all of these lines. First, copper tubing is typically used for refrigerant piping in air-conditioning systems. This tubing is available in various standard diameters and wall thicknesses. The nominal diameter of the tubing is expressed in terms of its 8 TRG-TRC006-EN
period one Refrigerant Piping Requirements notes outside diameter. This tubing must be completely free from dirt, scale, and oxide. New Type L or Type ACR tubing that has been cleaned by the manufacturer and capped at both ends is recommended for air-conditioning applications. The piping system is constructed by brazing copper tubes and fittings together. When brazing copper-to-copper joints, use BCuP-6* without flux. For copper-tosteel or copper-to-brass joints, use BAg-28* with a non-acid flux. The refrigerant piping must be properly supported to account for expansion, vibration, and the total weight of the piping. When a pipe experiences a temperature change, it is subject to a certain amount of expansion and contraction. Because the refrigerant piping is connected to the compressor, vibration forces are transmitted to the piping itself. Finally, the weight of the refrigerant-filled pipe and fittings must be supported to prevent the pipes from sagging, bending, or breaking. Avoid installing refrigerant piping underground. It is very difficult to maintain cleanliness during installation or to test for leaks. If underground installation is unavoidable, each line must be insulated separately, and then the lines must be waterproofed and protected with a hard casing (such as PVC). After the piping has been installed, the entire refrigeration circuit must be tested for leaks before it can be charged with refrigerant. This process typically involves pressurizing the entire piping system with dry nitrogen to examine each brazed joint for leaks. Each of these issues is discussed in greater detail in the Trane Reciprocating Refrigeration Manual. * Based on the American Welding Society’s (AWS) Specification for Filler Metals for Brazing and Braze Welding, publication A5.8–1992 TRG-TRC006-EN 9
period two Suction Line notes Refrigerant Piping period two Suction Line Figure 14 The first line to be considered is the suction line. Again, this pipe conducts lowpressure refrigerant vapor from the evaporator to the compressor. suction line Requirements for Sizing and Routing V Ensure adequate velocity to return oil to compressor at all steps of unloading V Avoid excessive noise V Minimize system capacity and efficiency loss Figure 15 Requirements for Sizing and Routing The diameter of the suction line must be small enough that the resulting refrigerant velocity is sufficiently high to carry oil droplets, at all steps of compressor unloading. If the velocity in the pipe is too high, however, objectionable noise may result. Also, the pipe diameter should be as large as possible to minimize pressure drop and thereby maximize system capacity and efficiency. 10 TRG-TRC006-EN
period two Suction Line notes suction line Sizing “Rules” old rules for R-22 new rules for R-22 minimum velocity 1,000 fpm (5 m/s) for vertical risers based on diameter of riser 500 fpm (2.5 m/s) for horizontal sections percentage of minimum riser velocity maximum velocity 4,000 fpm (20 m/s) 4,000 fpm (20 m/s) maximum pressure drop 3 psi (20 kPa) based on specific system requirements Figure 16 It may be helpful to compare the old “rules” for selecting the diameter of the suction line with the newer rules that result from changes in compressor technology, recent research, and the additional requirement to minimize system refrigerant charge. In the past, many suction lines for systems operating with Refrigerant-22 were sized to ensure that the minimum velocity in a vertical suction riser was more than 1,000 fpm (5 m/s), and the minimum velocity in a horizontal section was more than 500 fpm (2.5 m/s). Actually, the minimum allowable velocity in a suction riser depends on the diameter of the pipe. The minimum velocity required to carry oil droplets up a vertical riser is higher for a larger diameter pipe than it is for a smaller diameter pipe. This is due to the velocity profile of the refrigerant flowing inside the pipe. In a smaller diameter pipe, the higher-velocity refrigerant is closer to the inner walls of the pipe than it is in a larger-diameter pipe. For instance, while the minimum allowable velocity in a 2 1/8 in. (54 mm)-diameter suction riser is approximately 1,000 fpm (5 m/s), the minimum velocity in a 1 1/8 in. (28 mm)-diameter riser is only 700 fpm (3.6 m/s). While the old minimum-velocity limits were easy to remember, they may lead to the unnecessary use of double suction risers. The recommended maximum-velocity limit of 4,000 fpm (20 m/s) has not changed. A higher velocity inside the suction line may cause objectionable noise for those nearby. Another common rule, in a system operating with R-22, was to limit the pressure drop through the suction line to 3 psi (20 kPa). Although this was often thought to be a maximum limit, this value was originally intended to be only a recommendation, or guideline, for minimizing capacity and efficiency loss. Today, architects and HVAC system design engineers are placing the components of the refrigeration system farther apart, and this 3 psi (20 kPa) limit is often overly restrictive. Longer line lengths and the associated higher pressure drop can be tolerated, assuming that the loss of system capacity and efficiency is acceptable for the given application. Of course, it is still good TRG-TRC006-EN 11
period two Suction Line notes practice to minimize pressure drop, but an arbitrary limit places an unnecessary restriction on the system designer. suction line Process for Sizing 1 Determine total length of piping 2 Calculate refrigerant velocity at maximum and minimum capacities 3 Select largest pipe diameter that results in acceptable velocity at both maximum and minimum capacities 4 Calculate total equivalent length of straight pipe and fittings 5 Determine pressure drop due to pipe and fittings 6 Add pressure drop due to accessories Figure 17 Sizing Process Following are the steps to follow when selecting the proper diameter of the suction line: 1) Determine the total length of suction-line piping. 2) Calculate the refrigerant velocity at both maximum and minimum system capacities. 3) Select the largest pipe diameter that will result in acceptable refrigerant velocity at both maximum and minimum capacities. 4) Calculate the total “equivalent” length of piping by adding the actual length of straight pipe to the equivalent length of any fittings to be installed in the suction line. 5) Determine the pressure drop (based on the total equivalent length) due to the straight pipe and fittings. 6) Add the pressure drop due to any accessories installed in the suction line. To begin with, the refrigerant piping should be routed in the shortest and simplest manner possible, minimizing the total length of piping. From the initial layout, the total measured length of the suction line can be estimated. 12 TRG-TRC006-EN
period two Suction Line notes Unloading Refrigeration Circuits reciprocating compressor with cylinder unloaders scroll compressors manifolded on a single circuit Figure 18 If the system contains more than one independent refrigerant circuit, each circuit requires its own set of refrigerant lines. Therefore, the capacity of each individual circuit must be considered separately. Some refrigeration circuits include only one compressor that cycles on and off. This is very common in residential and light-commercial air-conditioning systems. In this case, the refrigeration circuit only operates at one capacity— fully on—so only the maximum system capacity needs to be considered. However, if the circuit contains a compressor that is capable of unloading, such as a single reciprocating compressor with cylinder unloaders, or if more than one compressor is manifolded together on a single circuit, such as multiple scroll compressors, then the minimum capacity of the circuit must also be determined. When the circuit unloads, less refrigerant flows through the system and the refrigerant velocity inside the piping is reduced. Recall that the diameter of the suction line must provide adequate velocity at both maximum and minimum capacities. At maximum capacity, the refrigerant velocity through the suction line will be the highest. Therefore, maximum capacity is important to ensure that the refrigerant velocity is below the upper limit of 4,000 fpm (20 m/s). At minimum capacity, the refrigerant velocity will be the lowest. Therefore, the minimum capacity of the refrigeration circuit is critical for ensuring that the refrigerant velocity is high enough to properly return oil to the compressor. It is important to note that the diameter of a vertical riser does not necessarily need to be the same as the diameter of the horizontal or vertical drop sections of pipe. The horizontal or vertical drop sections can often be selected one diameter larger than a vertical riser, reducing the overall pressure drop due to the suction line. This will be demonstrated later in this period. TRG-TRC006-EN 13
period two Suction Line notes suction line Determine Refrigerant Velocity velocity, fpm (m/s) 21 /8 (5 4) 25 /8 (6 7 31 ) /8 3 5 (79) 4 1 /8 ( 1 0 /8 (1 5) 30 ) 2) (2 7/8 11 /8 (2 8) 13 /8 (3 5 15 ) /8 (4 2) pipe diameter, in. (mm) 5) (1 5/8 3/4 (1 8) (25.4) 2) (1 1/2 3/8 (1 0) 5,000 2,000 (10.2) 1,000 (5.1) 500 (2.5) R-22 1 (3.5) 2 5 (7.0) (17.6) 10 (35) 20 (70) 50 (176) 100 (352) evaporator capacity, tons (kW) 200 (703) Figure 19 The refrigerant velocity inside a pipe depends on the mass flow rate and density of the refrigerant, and on the inside diameter of the pipe. The chart in Figure 19 shows the velocity of R-22 inside pipes of various diameters at one particular operating condition—40 F (4.4 C) saturated suction temperature, 125 F (51.7 C) saturated condensing temperature, 12 F (6.7 C) of superheat, 15 F (8.3 C) of subcooling, and 70 F (38.9 C) of compressor superheat. For an example system with an evaporator capacity of 20 tons (70.3 kW), the refrigerant velocity inside a 2 1/8 in. (54 mm)-diameter pipe at this condition is about 1,850 fpm (9.4 m/s). The easiest and most accurate method for determining refrigerant velocity is to use a computer program that can calculate the velocity for various pipe sizes based on actual conditions. However, if you do not have access to such a program, a chart like this may be useful. suction line Determine Refrigerant Velocity pipe diameter, in. (mm) 1 1/8 1 3/8 1 5/8 2 1/8 2 5/8 3 1/8 (28) (35) (42) (54) (67) (79) velocity, fpm (m/s) 20 tons (70.3 kW) 7,000 4,600 3,250 1,850 1,200 850 (35.6) (23.4) (16.5) (9.4) (6.1) (4.3) 10 tons (35.2 kW) 3,500 (17.8) 2,300 (11.7) 1,625 (8.3) 925 (4.7) 600 (3.1) 425 (2.2) Figure 20 Assume that this example 20-ton (70.3-kW) system contains one refrigeration 14 TRG-TRC006-EN
period two Suction Line notes circuit with two steps of capacity. Maximum system (evaporator) capacity is 20 tons (70.3 kW) and the circuit can unload to 10 tons (35.2 kW) of capacity. Using the chart in Figure 19 on page 14, the refrigerant velocity at both maximum and minimum capacities is determined for several pipe diameters. After these velocities have been determined, the largest acceptable pipe diameter is selected to minimize the overall pressure drop due to the suction line. When this system operates at maximum capacity, use of either the 1 1/8 in. (28 mm)- or the 1 3/8 in. (35 mm)-diameter pipes results in a refrigerant velocity that is greater than the recommended upper limit of 4,000 fpm (20 m/s). Again, these high velocities may cause objectionable noise, so these pipe sizes should probably not be considered. suction line Minimum Allowable Velocities pipe diameter, in. (mm) 3/8 (10) 1/2 (12) 5/8 (15) 3/4 (18) 7/8 (22) 1 1/8 (28) 1 3/8 (35) 1 5/8 (42) 2 1/8 (54) 2 5/8 (67) 3 1/8 (79) 3 5/8 (105) 4 1/8 (130) minimum velocity, fpm (m/s) riser horiz/drop horiz/drop 370 460 520 560 600 700 780 840 980 1,080 1,180 1,270 1,360 (1.9) (2.3) (2.6) (2.8) (3.1) (3.6) (4.0) (4.3) (5.0) (5.5) (6.0) (6.5) (6.9) 275 350 390 420 450 525 585 630 735 810 885 950 1,020 (1.4) (1.8) (2.0) (2.1) (2.3) (2.7) (3.0) (3.2) (3.7) (4.1) (4.5) (4.8) (5.2) Figure 21 Figure 21 shows the minimum allowable refrigerant velocity, for both a vertical suction riser and a horizontal (or vertical drop) section of suction line, for each standard pipe diameter. As mentioned earlier in this period, the minimum allowable velocity in a suction riser depends on the diameter of the pipe. The minimum velocity for a horizontal, or vertical drop, section is 75 percent of the minimum allowable velocity for a vertical riser of the same diameter. The minimum velocities listed in this table assume a worst-case operating condition of 20 F (-6.7 C) saturated suction temperature. This provides a safety factor, because a system will probably operate at this type of condition at some time in its life. TRG-TRC006-EN 15
period two Suction Line notes Select Suction Line Size circuit capacity, tons (kW) velocity inside 2 1/8 in. (54 mm) pipe, fpm (m/s) 20 (70.3) 1,850 (9.4) 10 (35.2) 925 (4.7) circuit capacity, tons (kW) velocity inside 1 5/8 in. (42 mm) pipe, fpm (m/s) 20 (70.3) 3,250 (16.5) 10 (35.2) 1,625 (8.3) minimum velocity for 2 1/8 in. (54 mm) pipe, fpm (m/s) riser horiz/drop horiz/drop 980 (5.0) 735 (3.7) minimum velocity for 1 5/8 in. (42 mm) pipe, fpm (m/s) riser horiz/drop horiz/drop 840 (4.3) 630 (3.2) Figure 22 Based on the minimum allowable velocities listed in Figure 21 on page 15, a 2 1/8 in. (54 mm) pipe will result in acceptable velocity, at both maximum and minimum capacities, for the horizontal and vertical drop sections of this example suction line. One size larger would result in a velocity that is too low when the system operates at minimum capacity. When the circuit unloads to 10 tons (35.2 kW), however, the velocity inside a 2 1/8 in. (54 mm) pipe—925 fpm (4.7 m/s)—will drop below the minimum allowable
The Trane Air Conditioning Clinic series is one means of knowledge sharing. It is intended to acquaint a technical audience with various fundamental aspects of heating, ventilating, an d air conditioning (HVAC). We have taken special care to make the clinic as uncommercial and straightforward as possible.
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Differences Between Classical and Operant Conditioning (see table 5.5, page 228) Classical Conditioning Operant Conditioning In classical conditioning, the organism learns an association between two stimuli—the CS and UCS (eg. food and tone)—that occurs before the behavior (eg. salivation). In operant conditioning, the organism learns an
Psychrometric Chart Air Conditioning Clinic TRC001GB.PPT American Standard Inc. 2003 . Air Conditioning Clinic TRG-TRC018-EN American Standard Inc. 2004 Dry-Bulb Thermometer . Air Conditioning Clinic TRG-TRC018-EN American Standard Inc. 2004 Wet-Bulb Thermometer .
The winter air conditioning uses a heat pump (refrigeration system operated in the reverse direction) and a humidifier. Depending upon the comfort of the human beings and the control of environment for the industrial products and processes, air conditioning can also be classified as comfort air conditioning and industrial air conditioning. .
Evacuate and Charge the Air Conditioning System (A7-E-4) 30 Chapter 15 - A/C System Diagnosis and Service Air Conditioning System Performance Test (A7-A-1, A7-A-3) 31 Air Conditioning Noise Diagnosis (A7-A-4) 32 Refrigerant Identification/Read Pressures (A7-A-5) 33 Leak Test the Air Conditioning System (A7-A-6) 34
User Persona: Clinic Managers Setup a Clinic Add a Clinic to Account Add Vaccine Inventory to Account Adding Vaccine Supply to a Clinic Setup clinic Schedule Schedule Clinic Hours of Operation Add Vaccine Administrators to a
From Ramsey/Sleeper Architectural Graphic Standards, 9th ed., The American Institute of Architects, 1994. 37 Overhangs Overhang variances are needed where curbs, sidewalks, and signage exist. Overhangs also come into effect where retaining walls are present. From Ramsey/Sleeper Architectural Graphic Standards, 9th ed., The American Institute of Architects, 1994. 38 Vertical Clearance Diagram .
