Applications
`Engineering
`Manual
`
`Multiple-Chiller-System
`Design and Control
`
`SYS-APM001-EN (March 2001}
`
`PAGE 1 of 98
`
`PETITIONER'S EXHIBIT 1222
`
`

`
`Multiple-Chiller-System
`Design and Control
`
`Mick Schwedler, applications engineer
`Ann Yates, information designer
`
`PAGE 2 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
` TRAN?
`
`Preface
`
`This manual examines chilled-water-system components, configurations,
`options, and control strategies. The goal is to provide system designers with
`options they can use to satisfy the building owners‘ desires, but this manual is
`not intended to be a complete chiller-system design manual.
`
`System designers may get the most use from this manual by familiarizing
`themselves with chilled-water-system basics and understanding the benefits of
`various options. Thereafter, when a specificjob will benefit from these
`advantages, consult appropriate sections of the manual in detail.
`
`The Engineers Newsletters that are referenced in this manual are available at:
`www.trane.com/commercial/Iibrary/news|etters.asp
`
`The Trane Company, in proposing these system design and application
`concepts, assumes no responsibility for the performance or desirability of any
`resulting system design. System design is the prerogative and responsibility of
`the system designer.
`
`SYS-APM001-EN
`
`(9 2001 American Standard Inc. All rights reserved
`
`PAGE 3 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
` rmusr
`
`Contents
`
`Introduction ......................................................................................... ..1
`
`Chilled-Water-Plant Basics ............................................................. ..2
`
`Chilled-water distribution system ........... ..
`Condenser-water system .............................. ..
`Controls .................................................................................................. .. 11
`
`Chilled-Water-System Options .................................................. ..13
`Chi||ed— and condenser—water temperatures ................ ..
`Chi||ed- and condenser-water flow rates ...................... ..
`
`Misconceptions about low-flow rates . . . . . .
`
`.
`
`. .
`
`. . . . .
`
`.
`
`. . . . . . .
`
`.
`
`. . . ..24
`
`System Configurations ................................................................. ..27
`Parallel chillers ....................... ..
`Series chillers ................................................ ..
`
`Primary—secondary (decoupled) systems ............................................ ..31
`
`Pumping Arrangements ................................................................. .. 36
`Flow-based control ................................................................................. ..38
`
`Chiller sequencing ................................................................................. ..39
`
`Variable-Primary-Flow Systems ................................................ .. 40
`VPF advantages ...................................................................................... ..4’l
`VPF caveats ............................................................................................ ..4’l
`
`Chiller sequencing ................................................................................. ..43
`
`Chilled-Water-Control Options ................................................. .. 47
`Chi||ed—water reset—raising and lowering ........................................... ..47
`Critical valve reset .................................................................................. ..48
`
`Design Considerations .................................................................. ..49
`Chilled-water pump configurations ....................................................... ..49
`Bypass line sizing .................................................................................... ..50
`Amount of fluid in the loop .................................................................... ..50
`Plant expansion ....................................................................................... ..5’l
`
`SYS—APM001—EN
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`PAGE 4 of 98
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`PETITIONER'S EXHIBIT 1222
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` TRAN?
`
`Contents
`
`Chi||ed-Water- System Variations .... ..
`Heat recovery ......................................................................................... .. 54
`Preferential loading ............................................................................... ..54
`Unequal chiller sizing ............................................................................ ..58
`Series-counterflow application .............................................................. ..58
`Applications outside the chi||er's range ............................................... ..60
`
`Chilled-Water-System Issues ...................................................... .. 63
`Low AT syndrome .......................................... ..
`Check valve in the bypass line ............................................................... ..63
`Failure recovery ...................................................................................... ..64
`Alternative energy sources .................................................................... ..64
`Contingency ........................................................................................... ..66
`
`Condenser-System Variations .................................................... .. 69
`Condenser flow configurations ............................................................ ..69
`Coo|ing—tower—fan control methods ..................................................... ..71
`Plate-and-frame heat exchanger .......................................................... .. 72
`Well, river, or lake water ........................................................................ ..72
`
`Condenser-water temperature control ................................................. .. 72
`Condenser—water pump options ............................................................ ..73
`Retrofit opportunities ............................................................................ .. 75
`
`Conclusion .......................................................................................... .. 78
`
`Glossary ............................................................................................... .. 79
`References .......................................................................................... .. 82
`
`Index ...................................................................................................... .. 85
`
`SYS—APM001—EN
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`PETITIONER'S EXHIBIT 1222
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` rmust
`
`Contents
`
`Figures
`Figure 1
`Figure 2
`Figure 3
`Figure 4
`Figure 5
`Figure 6
`Figure 7
`Figure 8
`Figure 9
`Figure 10
`Figure 11
`Figure 12
`Figure 13
`Figure 14
`Figure 15
`Figure 16
`Figure 17
`Figure 18
`Figure 19
`Figure 20
`Figure 21
`Figure 22
`Figure 23
`Figure 23a
`Figure 24
`Figure 25
`Figure 26
`Figure 27
`Figure 28
`Figure 29
`Figure 30
`Figure 31
`
`2
`Typical vapor—compression chiller ..................................... ..
`Valve-controlled loads ........................................................ .. 6
`Uncontrolled coil ................................................................. ..
`7
`
`Simplified distribution system ........................................... .. 9
`Chi||ed—water—system performance at part load ............... .. 19
`Annual system operating costs ......................................... .. 23
`System energy comparison (no pipe) ............................... .. 25
`Parallel chillers with single, common pump .................... .. 27
`Parallel chillers with separate, dedicated chiller pumps
`28
`Series chillers ...................................................................... .. 29
`
`Decoupled arrangement ..................................................... .. 31
`Production loop ................................................................... .. 33
`Distribution loop ................................................................. .. 34
`Campus pumping arrangement ........................................ .. 36
`Tertiary pumping arrangement .......................................... .. 37
`Decoupled system supply tee ............................................ .. 37
`Temperature-sensing .......................................................... .. 38
`Variable-primary-flow system ............................................ .. 40
`Doub|e—ended decoupled system ...................................... .. 53
`Parallel preferential loading arrangement ........................ .. 55
`Sidestream preferential loading arrangement ................. .. 56
`Plate-and-frame heat exchanger ....................................... .. 57
`Series—counterf|ow arrangement ....................................... .. 59
`Equal lift concept ....................................................... .. 59
`Flow rate out of range for equipment ............................... .. 60
`Temperatures out of range for equipment ....................... .. 61
`Precise temperature control, multiple chillers ................. .. 62
`Failure recovery ............................................................ .. 64
`Manifolded condenser-water pumps ................................ .. 69
`Chiller-tower energy consumption .................................... .. 73
`Decoupled condenser-water system ................................. .. 74
`Chi||er—tower selection with different chiller capacities..... 76
`
`SYS—APM001—EN
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`PAGE 6 of 98
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`PETITIONER'S EXHIBIT 1222
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` TRAN?
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`Contents
`
`Tables
`Table 1
`
`Table 2
`Table 3
`Table 4
`Table 5
`Table 6
`Table 7
`Table 8
`Table 9
`Table 10
`Table 11
`
`Recommended chi||er—monitoring points per
`ASHRAE Guideline 3-1996 ................................................. ..11
`
`Standard rating conditions for absorption chillers ........... ..15
`Standard rating conditions for chilled-water systems ..... ..16
`Low—f|ow conditions for chi||ed—water pump .................... ..17
`Low—f|ow conditions for cooling tower .............................. ..17
`Low-flow conditions for condenser-water pump .............. .. 17
`Total system power ............................................................. ..18
`Effect of decreased water temperature
`Retrofit capacity changes .................................................... ..21
`Reduced flow-rate effect ..................................................... ..24
`
`Flow-rate-fluctuation examples .......................................... ..44
`
`SYS—APM001—EN
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`PAGE 7 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
` TRANEE
`
`Introduction
`
`Many building owners continually search for solutions that allow their
`businesses to offer higher quality, and to be more competitive and profitable.
`HVAC systems designers often use chi||ed—water systems to provide high-
`quality, cost-effective air conditioning for building owners. With the advent of
`more flexible chillers, system-level controls, and software analysis tools, the
`number of chilled-water-systems options has exploded.
`
`SYS-APM001-EN
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`PAGE 8 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
`Chilled-Water-Plant Basics
`
`Chillnrl-walor plants consist of Those flJ|'If!TiI.".mfl| parts:
`
`Chillers that produce chilled water
`
`Loads, often satisfied by soils. that transfer heat from air to water
`
`Chilled-water distribution pumps and pipes that send chilled water to the
`previously mentioned loads
`
`Cr.-nrlnnsrer-wntr.-r pumps. pipes. and cooling towers that rrgjricl hunt
`(for wa1.or—r;oo|eLi chillers}
`
`Controls that coordinate the operation of the mechanical con'iponer'-ls
`together as a systrsrn
`
`Chiller
`
`Thorn arr! :1 variety nl watt.-r r:hI||r:r typos. Most commonly, they arr! ahsnrpllnn,
`ceritrifugal. |'1Is|i:.'a| rotary. and scroll. Surm-J recipruuatirig LIl"|i”l:.'FS are also
`available. Chillers can be either air- or water-cooled. Major vapor-compression
`chillr.-r cnrnpnnnnts il'1¢‘.|lJdI': an Evaporator, :1 cnmprnssorfis}, .1 cnnrlrsnsrsr, and
`an exparislori deuicolsj. This manual discusses the r;hil|er's evaporator and
`condenser and their relationship to the chi||ed—i.n.-ater plant.
`
`Figaro 1 Typical vapor-compression chiller
`
`Compressor
`
`I-
`
`:-
`
`I._
`
`Cond on star
`
`Eva porat-or
`
`SVSAPMGU1-EN
`
`PAGE 9 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
` TRANEE
`
`Chilled-Water-Plant Basics
`
`Evaporator
`
`The evaporator section of a water chiller is a shell-and-tube, refrigerant-to-
`water heat exchanger. Depending on the chi||er's design, either the refrigerant
`or the water is contained within the tubes.
`
`In a flooded she||—and—tube evaporator, cool, liquid refrigerant at low-
`pressure enters the distribution system inside the shell and moves
`uniformly over the tubes, absorbing heat from warmer water that flows
`through the tubes.
`
`In a direct-expansion (DX) shell-and-tube evaporator, warmer water fills the
`shell while the cool, |ower—pressure liquid refrigerant flows through the
`tubes.
`
`In either design, there is an approach temperature, which is the temperature
`difference between the refrigerant and exit water stream. The approach
`temperature is a measure of the heat transfer efficiency of the evaporator.
`
`Effect of chilled-water temperature
`
`For a given chiller, as the leaving chi||ed—water temperature drops, the
`refrigerant temperature and pressure must also drop. Conversely, as the
`leaving chilled-water temperature rises, so do the refrigerant temperature and
`pressure. When the leaving chilled-water temperature changes, the work a
`compressor must do also changes. The effect of leaving chilled-water
`temperature change on power consumption can be 1.0 percent to 2.2 percent
`per degree fahrenheit [1.8 percent to 4.0 percent per degree Celsius]. Always
`consider the energy consumption of the entire system—not only the chiller. It is
`important to remember that although reducing leaving chilled-water
`temperature penalizes the chiller, it may benefit the pumps because less water
`is pumped through the system. System interactions are covered in more detail
`in the next section Chilled—Water—System Options.
`
`Effect of chilled-water flow rate
`
`Since the evaporator is a heat exchanger, it is sensitive to water flow rate.
`Excessive flow may result in high water velocity, erosion, vibration, or noise.
`Insufficient flow reduces heat-transfer efficiency and causes poor chiller
`performance. Some designers have concerns over low flow rates causing
`fouling. Generally, as Webb and Li?’ noted, these concerns are unwarranted
`since the chilled-water loop is a closed system, thus reducing the chances of
`materials entering the system and causing fouling. Chi||ed—water flow through
`the chiller must be kept within specific minimum and maximum limits. Contact
`the manufacturer for these limits.
`
`SYS-APM001-EN
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`PAGE 10 of 98
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`PETITIONER'S EXHIBIT 1222
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`

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` TRAN?
`
`Chilled-Water-Plant Basics
`
`Some chiller controls can accommodate very little flow variation during
`machine operation.2 Other, more sophisticated, chiller controls allow some
`flow variation. Some chillers can tolerate f|ow—rate variations of as much as 30
`
`percent per minute or greater, while others can only tolerate up to 2 percent per
`minute. It is important that chiller capabilities are matched to system
`requirements. Contact the chiller manufacturer to determine allowable rate of
`flow variation before varying the flow through the evaporator in a chiller. Flow
`variation is discussed in detail in the section VariabIe—Primary—FIOw Systems,
`page 40.
`
`Water-cooled condenser
`
`To cool a building or process, the transferred heat must ultimately be rejected.
`The total amount of heat rejected includes the sum total of the evaporator load,
`the compressor work, and the motor inefficiency. In a hermetic chiller, where
`the motor and compressor are in the same housing, these loads are all rejected
`through the condenser. In an open chiller, where the motor is separate from the
`compressor and connected by a shaft, the motor heat is rejected directly to the
`surrounding air. The evaporator load and the compressor work are rejected
`through the condenser and the motor heat must be taken care of by the air-
`conditioning system.
`
`Effect of condenser-water temperature
`
`For a given chiller, as the leaving condenser-water temperature rises,
`refrigerant temperature and pressure also rise. Conversely, as leaving
`condenser-water temperature drops, so do refrigerant temperature and
`pressure. As the refrigerant pressure and temperature changes, the work a
`compressor must do also changes. The effect of |eaving—condenser—water
`temperature change on power consumption can be 1.0 percent to 2.2 percent
`per degree fahrenheit [1.8 percent to 4.0 per degree celsius]. Always consider
`the energy consumption of the entire system—notjust the chiller. It is
`important to remember that although raising the leaving condenser-water
`temperature penalizes the chiller, it may benefit the pumps and cooling tower
`through the use of reduced flow rates and higher thermal driving-forces on the
`tower. System interactions are covered in more detail in the section Condenser-
`System Variations, page 69.
`
`Effect of condenser-water flow rate
`
`Since the condenser is a heat exchanger, it is sensitive to water flow rate. For
`example, excessive flow may result in high water velocity, erosion, vibration, or
`noise, while insufficient flow reduces heat transfer efficiency and causes poor
`chiller performance. Therefore, condenser-water flow through the chiller should
`be kept within a specific range of limits, except during transient startup
`
`SYS-APM001-EN
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`PAGE 11 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
`Chilled-lllilater-Plant Basics
`
`eonrlitions. Contact the manutaeturer tor these limits. Some ehillers may allow
`extended operation below the selected flow rates.
`
`It water velocity through the condenser tu hes is too low for significant periods
`of lime and the water is extremely hard, |ong—term fouling of lhe tubes may
`also occur. Webb and Li!’ tested a number of internall3r—enhanced oendenser
`tubes at low velocity [351 ftfs [‘l.lC|'.i' rri.ls]} and high water hardness. While they
`found that some of the internally-enhanced tut:-es fouled. in the long term they
`concluded:
`
`El-ecause of the high hardness and low water velocity used in ttiese
`tests. we do not believe that the fouling experienced is typical of that
`expected in eomrnereial installations. With use 01 good maintenance
`practices and water quality corilrol, all of the tubes tested are probably
`stiitaole for lor1g—terrTi-fouling applications.
`
`It is iiripuitaril to remernber that a chillei selected For low Flow {as discussed ir1
`the next section Cl:i'lIecI-Water-System Options] does not rtecessarilgr have low
`velocity through its tubes. It tube toulinq is a ITIBJDT eoneern, eonsieler the use of
`srnuoth. rather than inter riaI|y—erihar1ced. tubes in the contleriser for ease of
`cleaning.
`
`Air-cooled condenser
`
`Dtwiotisly. all-cooled chillers do not use cu-nderiser-water. since they FBJECI their
`heat by having ambiertt air passed across refrigerant-to-air heat exchangers Ir‘-
`paelcagerl air-eoolerl ehillers, the manufacturers attempt to provide optimal
`perforrttarice by slagi rig fans in resporise to chiller load and amtiient. t.1ry—t:u|l:r
`temperature.
`
`Loads
`
`In comfort-cooling applications. loads are usually satisfied by air handlers
`equi paper] with eoils to transter heat from eonrlitionerl spaee air to eireulating
`chilled-water. Air is thus cooled and Lletitirtiidified as it passes across the finned
`surface of the cooling coils. Since the psychrometric process of cenditieriing air
`takes plaee at the coils, selection of the optimum I.".DIl sire and type trorn the
`wide variety available is important for proper system perforrriarice.
`
`Ei‘r"':'r-.-5'.F'|"..I'||3I|I|l -EN
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`PAGE 12 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
`Chilled-Water-Plant Basics
`
`Sr.-me sp-eeralizeel process leads do not Involve enoling air. Instead, they may
`irwulve heat trarisfer directly within a piece of process eq uiprne I'll. such as the
`coollrtgjacl-tet ofan in_jectiort-molding machine Heat transferred from the loads
`een be controlled In F; number of ways:
`
`I Three—way valve
`
`Two-way value
`
`Varial}Ie—speed pump
`Uncontrolled coils
`
`Three-way valve load control
`
`Pl three-way control valve regulates the amount of water passing through a coil
`in response reloads. The valve bypasses unused water around the cell and
`requires i:l cortstartt flow of water in the systerrt. regardless of load. A drawback
`of this |:r_\.-pass is that the temperature of the water lean-irtg the three—wa3,r value
`is reduced at part-lnael conditions. This can he a m:1_jnr cause of Sn-Called "low
`AT 5_\,rridrurrIe" dis-r:LIsset.1 on page 63 in the settler: Ctri'iIed-Water-Systerrt
`Issues. Three-way "l.|'£I|'u"E5 are used in nteny existing systems
`
`Figure 2 Value-controlled loads
`
`§' Three-Way Valve
`
`9 r"""'w“3" 1"'“'"°
`
`Two-way value load control
`
`A two-way, water In odulaling valve at the coil p-erforrns the same water
`throttling function as the three-way valve. The coil sees no difference between
`these two meth eds. The ehi llerl—watr:r system. however. sees a great difference.
`In the ease of the two-way value. all flow in the coil i'.2Ilt.'L.llt Is thruttled. No water
`is bypassed Cortseciuentlg-,r. a system using two-way valves is a variable-flow
`ehillerl-water system. The temperature nt the water leaving the cell is net
`diluted by bypass water so at parl-Iuatzl l'_2U-fIL1l1.lU-l'1‘_i. the syslern returrrwater
`[El"I'lp€l'EI[L.li'E i5 hlgt'IE'.I' [t'IEii"l With [t'Ii'€€-WW3)‘
`VBIVE CDl"'lIi'O|.
`
`S'fS..'.'.P|'v'lflU1-EN
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`PAGE 13 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
`Chilled-llllater-Plant Basics
`
`Variable-speed pumping load control
`
`By using a pump for each coil. the flow may be controlled by varying the pump
`speed. In such systems, there may be no central values at the cell. This can
`reduce both the value and the valve lfl‘_i[i:lHi:ll.IL.‘Irl costs.
`
`Uncontrolled coils
`
`Figure 3 stiuws ::i Liurttrul '|i'i:lFI-E:I1.lUrl using an uricorttiulled or "wild "i;ui|. In this
`53.-stern. control of the conditioned air supply is executed by face-artd-bypass
`dampers that permit a portion nt the air to bypass the cell surface. Advantages
`L31" the strategy are the eliriiiriatiori of curitrul values and llTI[.‘rl|'..'I‘.I'EI:.l part-load
`dehumidification. P. disadvantage is that all the water is puinpecl all the time:
`however, in systems with uergi small water pressure drops, this system
`at rarigerrieril rriay work ecoriornically.
`
`Fig: re 3 Uncontrolled coil
`
`Hype ss Damper
`
`Air I lancllcr
`
`Ctmlrzd Air l|.I'li itture
`
`Face Damper
`
`Chilled-water distribution system
`
`Chilled water is circulated through fixed piping—rncst commonly steel. copper,
`pr p|astic—that connects the chiller with uarir.-us load terrninals. Piping is sited
`to meet a project's pressure less. water velocity. and coristructiuri cost
`parameters Pressure drop is overcome by the use of a chilled-water pump.
`
`S‘r".~'r-.-5.F'|"'..I'||II|I|1-El\.|
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`PAGE 14 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
` TRAN?
`
`Chilled-Water-Plant Basics
`
`Chilled-water pump
`
`The purpose of the chilled-water pump is to circulate chilled water within the
`loop. Generally, the pump must overcome the frictional pressure losses caused
`by the piping, coils, and chiller and the pressure differential across open control
`valves in the system. The pump, while working at the system static pressure,
`does not need to overcome this static pressure. For example, in a forty—story
`building the pump need not overcome the static pressure due to those forty
`stories.
`
`The pump is typically located upstream of the chiller, however it may be
`anywhere in the system, provided that the pump:
`
`I meets the minimum pump net positive suction—head requirements. That is,
`the system pressure at the pump inlet must be both positive and high
`enough to allow the pump to operate properly;
`
`maintains the minimum dynamic pressure head at critical system
`components (usually the chiller). If the dynamic pressure head is not high
`enough at these components, proper flow will not be established through
`them;
`
`accommodates the total pressure (static head plus dynamic head) on
`system components such as the chi||er's evaporator, valves, etc.
`
`Note that the pump heat is added to the water and must be absorbed by the
`chiller. Generally, this represents a very small temperature increase.
`
`Multiple pumps are often used for redundancy. Depending on the terminal
`control devices and system configurations, the chilled-water pumps may be
`either constant or variable-flow.
`
`SYS-APM001-EN
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`PAGE 15 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
`Chilled-Water-Plant Basics
`
`Distribution piping
`
`By itself. the distribution system is easy to understand. Figure Ji shows a
`simplified distribiitinn system consisting not multiple er.-nlinri coils, rraeh
`coritmlled by e Lrierrnostet trial regulates the flow in its respective coil. The
`valves may be either three-way or two-way. es pre-i-iously discussed. three-way
`valves rndiiirn constant watnr tlr.-w, whlln two-way values allow the water flow
`in the systerrl to vary. As. flow var ies, the [_'lL|rl1[J rrlay sirriply FIIJI-_'.' its curve U-I use
`a method orflow control such as a variable-speed drive See the section System
`Cnn.figiJ'rarinit5, on page 2?. tor a detailed diseiissinn of distrihiitinn-system
`LJ[JLILJrIS.
`
`Figire ll Simplified distribution system
`
`Expansion
`
`Di Htri huti nun
`
`Piping
`
`25.35 ASHRAE “Ix.-_4C 5J_,_,:mm_,; and
`fqu.-';_}_r;.;-;_~,u;-;.Ii;.-,1.;.';_i.-_wi¢_ cmpmr 12_
`I |_i"Jr0nI': | lf-‘atirig and Cslollng S}'='=lDrT1
`|1'n-aigrii c:nn|e'IInH 'eI:liiItmrIr'I| ri:lc‘.rnrI='.t‘.
`lFlhZJFl'i1.5Ill[iFll2l[1H'l[!l2i2lI'l'l[H2li1|Z!I'II£!-i|ZJi.=I
`r:hi||i:i1w;|ti:r tli-stritiiititzuri 5-:3,”-.lt:rri.
`
`The distribution system may contain other components, such as an expansion
`
`tank, control valves, [1-alanci rig valves. check valves, and an air separator. to
`name at
`|'e'.'u'_ The Llerisily. arid llieielure Lhe '-."IJ|L||'l1B. ul Lhe water in .3 "c|useLl"
`chilled-water ciistribiitiort system varies as it undergoes changes in
`tnmpnratiirn. The oi-:pai‘i'.-'.inn tank allows fnr this nxpaitsmn and |.':l‘H‘ITf£'1CTll‘.l|‘I nt
`.,u._.j._E[ uulunle
`
`S‘r":i-.¢iF'|"'.I'||IIE|1-EN
`
`PAGE 16 of 98
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`PETITIONER'S EXHIBIT 1222
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`

`
` TRAN?
`
`Chilled-Water-Plant Basics
`
`Condenser-water system
`
`As in chi||ed—water distribution systems, condenser—water system piping—most
`commonly steel, copper, or p|astic—is sized to meet a project's operating
`pressure, pressure loss, water velocity, and construction cost parameters.
`Pressure drop through piping and the chi||er's condenser, plus the cooling-
`tower static lift, is overcome by use of a condenser-water pump.
`
`Cooling tower
`
`To reject heat, water is passed through a cooling tower where a portion of it
`evaporates, thus cooling the remaining water. A particular cooling tower's
`effectiveness at transferring heat depends on water flow rate, water
`temperature, and ambient wet bulb. The temperature difference between the
`water entering and leaving the cooling tower is the range. The temperature
`difference between the leaving water temperature and the entering wet-bulb
`temperature is the approach.
`
`Effect of load
`
`As the building |oad—or heat rejection—decreases, range and approach also
`decrease. This means that when the building is at part load, the cooling tower
`can provide colder water at the same ambient wet—bu|b temperature.
`
`Effect of ambient conditions
`
`As ambient wet—bu|b temperature drops, the approach—at a constant load—
`increases. This must be considered when cooling-tower-control strategies are
`developed. Detailed descriptions of these conditions appear in the subsection,
`Chiller-tower energy balance, page 72. For additional information, refer to 2000
`
`ASHRAE1HVAC Systems and Equipment Handbook, Chapter 36, “Cooling
`Towers."
`
`SYS-APM001-EN
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`PETITIONER'S EXHIBIT 1222
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`

`
` TRANEE
`
`Chilled-Water-Plant Basics
`
`Controls
`
`The chi||ed—water supply temperature is usually controlled at the chiller. Most
`commonly, supply water temperature is used as the sensed variable to permit
`control of chiller capacity to meet system load demand. Supply-temperature
`control strategies may be used on either constant- or variable-flow systems. As
`previously discussed, flow control is executed at the load terminals using three-
`way or two—way valves, or separate pumps for each coil.
`
`Control capabilities run the gamut from slow-acting pneumatic controls, to
`electromechanical controls, to sophisticated digital controls that use algorithms
`tuned to give superior performance.
`
`Chiller control
`
`Today's chiller controls are capable of doing more than simply turning the
`chiller on and off. At a minimum, these controls should monitor:
`
`I Safety points such as bearing temperatures and electrical points that, when
`out of range, may cause motor failure.
`
`Data points that may cause operational problems if corrective action is not
`taken. An example is low chi||ed—water or refrigerant temperature, which
`may result in freezing in or around the evaporator tubes.
`
`General points that should be logged daily to ensure proper chiller
`performance.
`
`Table 1 lists the ASHRAE-recommended monitoring points.
`
`Table 1 Recommended chiller-monitoring points per ASHRAE Guideline 3-1996
`Flow
`Flow
`
`chmed
`Water
`
`Inlet Pressure
`Inlet Temperature
`Outlet Pressure
`
`condenser
`Water
`
`Inlet Pressure
`Inlet Temperature
`Outlet Pressure
`
`Outlet Temperature
`Approach Temperature
`EvaporatorT Condenser
`Refrigerant Pressure
`Refrigerant Temperature
`Level
`
`Outlet Temperature
`Approach Temperature
`_
`Refrigerant Pressure
`Refrigerant Temperature
`Level
`
`Pressure
`Temperature
`Additional Required
`
`Refrigerant Compressor Discharge Temperature
`Additional Required
`Vibration Levels
`
`SYS-APM001-EN
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`PETITIONER'S EXHIBIT 1222
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`

`
` TRAN?
`
`Chilled-Water-Plant Basics
`
`In addition to monitoring data, it is vital that the chiller controls alert operators
`to possible problems. Diagnostic messages are necessary for the operator to
`respond to safety issues and data points that are outside normal operating
`ranges.
`
`While communicating these diagnostic messages is a requirement, some chiller
`controls include factory-installed programming that responds to the diagnostic
`messages. For example, when the chi||ed—water temperature nears freezing, the
`chiller sends a diagnostic message and adapts its operation by reducing the
`compressor capacity, raising the chilled-water temperature to a safer condition.
`
`Finally, the chiller controls should communicate with a system-level controller.
`There are many system aspects that are outside the chi||er's direct control, such
`as condenser—water temperature and the amount of fluid flowing through the
`evaporator and condenser. To minimize the system energy costs, the system
`controls must coordinate chiller, pump, cooling-tower, and terminal-unit
`controls. This can only be done if adequate information is communicated from
`each system component to the system-level controls.
`
`Pump control
`
`In so-called constant flow systems, the pumps are either on or off, providing
`relatively constant flow when in the on position. In practice, some flow
`variation will occur as system pressure drop changes. In a variab|e—f|ow system,
`pump control is most often performed by maintaining a pressure differential at
`a selected point in the system. For example, a variable-speed drive will increase
`its speed if the sensed pressure differential is too low, or slow down if the
`pressure differential is too high. The control point is selected to minimize over-
`pressuring the system and to assure adequate flow at all critical loads. Optimal
`pumping control strategies are addressed in Critical valve reset, page 48.
`
`Chapter references
`
`1
`
`2000 ASHRAE HVAC Systems and Equipment Handbook, Chapter 12,
`Hydronic Heating and Cooling System Design and Chapter 36, Cooling
`Towers, American Society of Heating, Refrigeration and Air-Conditioning
`Engineers.
`
`Schwedler, M., PE and Bradley, B.; “An Idea for Chi||ed—Water Plants Whose
`Time Has Come...Variab|e-Primary-Flow Systems,” Engineers Newsletter,
`Volume 28, No. 3, The Trane Company, 1999.
`
`Webb, R.L. and Li, W.; “Fou|ing in Enhanced Tubes Using Cooling Tower
`Water, Part I: Long-Term Fouling Data," International Journal of Heat and
`Mass Transfer, 2000.
`
`SYS-APM001-EN
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`PAGE 19 of 98
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`PETITIONER'S EXHIBIT 1222
`
`

`
` TRIKE
`
`Chilled-Water-System Options
`
`There arr: many chilled-walnr-system design option s; however. In a ha sic snnsn.
`eacli option is a furi:.'Lir.:r1 of flow. Lerrrp-erature. systerri Liurtfiguratiurr. and
`control. This section discusses the effect of flow rate and temperature
`decisions.
`
`It is important to remember that temperatures and flow rates are variables By
`_jur:li:Inus snlr.-min-n pl tl'rr.=sr.- unrrahlns. chillr.-r:l-watt.-r plants can be designed tr.-
`lJDLl'1 satisfy r:hil|et.l-water req Liirerneriis and operate cost effectively.
`
`Chilled-water systnnts arr: nttrtn t'l£'.‘filtj|‘If.‘l'l using tlriiar rates and trrrnprtraturns
`applied