Central Chilled Water Systems (CCWS)
Design/Control Manual Of
CHICAGO LARGE OFFICE
ASHRAE DESIGN&
(min kW) DESIGN
Kirby Nelson PE5/5/2023
Kirby Nelson PE Page 1
Contents: Chicago Design ManualPrefaceIntroductionCHAPTER (1) ASHRAE Design & (min kW Design) -Peak Design Day Performance -Average Summer Day Performance -Average Spring/Fall Day Performance -Average Winter Day PerformanceNOMENCLATUREDetail analysis will be added.
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PREFACEDOE building energy models do not work, this Design Manual presents a modeling approach that does. Following is a brief summary of the characteristics of system energy equilibrium (SEE) models and the (SEE) model experience of the author.(SEE) ModelSystem energy equilibrium (SEE) models and schematics can be developed for any condition of weather and operational conditions that may occur in a real system. The requirement for the (SEE) model/schematic is always the same; it must duplicate the performance of the equipment that make up the system and it must obey the laws of thermodynamics and physics and include the nonlinear characteristics of the components of the system. The (SEE) model/schematics defined here assume all chillers are of the same size and model and the air handlers are the same size and model and equally loaded.Math models that duplicate the real time performance of systems are standard practice in the space program and in the development of military products such as missiles, cannons, and other complex systems. The System Energy Equilibrium (SEE) Model presented here duplicates the thermodynamic and nonlinear performance of real systems and therefore can define the best possible performance of a system consistent with the design and control concepts incorporated in the design i.e. the theoretical performance of the system as designed.The author has found that the design and control concepts advocated by ASHRAE and Pacific Northwest National Laboratory (PNNL) yields a design that requires more demand kW and therefore energy than does a more conventional design and control strategy. These differences in design and control are detailed below.
Kirby Nelson experienceThe following is a brief history of Kirby’s experience in System Energy Equilibrium (SEE) Modeling and analysis.
System Energy Equilibrium (SEE) modeling is not a new concept. The author was involved in this approach to modeling in the 1970’s designing military products and then as corporate energy manager for Texas Instruments Inc. modeling building systems.The concept is to simply write the basic physics and thermodynamic equations of the system and simultaneously solve the set of equations with a computer. The results will duplicate the performance of the real system if the equations are correct; nonlinear characteristics input and equipment efficiencies input. The equations can be, and should be, corrected by iterating between the real performance data verses the model and updating the model equations. The first HVAC paper published using this approach was in the ASHRAE Journal of December 2006. "7 Upgrades to Reduce Building Electrical Demand"In March 2010 he had an article in Engineered Systems "Central Chilled Water System Modeling" & July 2010 an HPAC article on chiller selection "Central-Chiller Plant Modeling"In 2011 a 5 article series in HPAC dealing with Primary/Secondary vs. Primary-Only pumping. The second article dealt with the efficient control of a P/S plant and the third article with efficient control of a P-only plant. The fourth article was "Anatomy of Load delta-T" and the fifth added the building and air side equipment to the analysis.In 2012 Kirby presented two advance technical papers at ASHRAE Chicago 2012. (CH-12-002) title “Simulation Modeling of a Central Chiller Plant” and (CH-12-003) "Simulation Modeling of Central Chilled Water Systems".Since Chicago he has continued to develop the concept of (SEE) modeling and has entered into discussions on ASHRAExCHANGE on the ASHRAE web site. Kirby’s analysis of these issues and others to follow can be viewed at http://kirbynelsonpe.com/
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INTRODUCTIONSeveral events give cause for concern regarding the capabilities of DOE models and the misunderstanding that has developed and become part of the ASHRAE culture.DOE Energy Models:40 years after the oil embargo of 4th quarter 1973 an air side model is not part of the DOE, PNNL, ASHRAE tool bag as evidenced by the ASHRAE Journal of July 2014 page 70 & September 2014 page 10. Limit heating air temperature:Table 5.2 of the (PNNL) study calls for “Limit reheat temperature to 20 degrees F above room temperature for better air distribution effectiveness”. The (PNNL) study also states “EnergyPlus limitations make it impractical to capture savings. May revisit after upgrade to EnergyPlus”. The (SEE) model finds this control strategy significantly increases the energy consumption of the system. The fact that (PNNL) believes this control strategy will reduce energy consumption is troubling. ASHRAE Journal Plant Design:The ASHRAE Journal approach to plant design as given by a series of article beginning July 2011 by Taylor results in significantly greater plant kW than a “(min KW) Design” as presented here.Pacific Northwest National Laboratory study of ASHRAE Standard 90.1-2010. The study by Pacific Northwest National Laboratory (PNNL) of ASHRAE Standard 90.1-2010 defines a large office building that is used as the base building for this study. The (PNNL) study defines the building characteristics, schedules, control, and HVAC equipment of the large office building defined here as the “ASHRAE Design”. Further the ASHRAE Journal of July 2011 defines “Optimizing Design & Control of Chilled Water Plants”, which is used to define the plant of the “ASHRAE Design”. This (SEE) model analysis has found that the “ASHRAE Design” calls for design and control concepts that significantly increase the energy consumption of the system compared to a “(min kW) Design”. The “(min kW) Design” is, I believe, less first cost. The (PNNL) study can be viewed at;
http://www.energycodes.gov/sites/default/files/documents/BECP_Energy_Cost_Savings_STD2010_May2011_v00.pdf orhttp://www.energycodes.gov/achieving-30-goal-energy-and-cost-savings-analysis-ashrae-standard-901-2010BUILDING DEFINEDThe (PNNL) study defines the building as given by the Figure, a 13 story office with 498,600 square feet of air conditioned space.
Building description The peak design temperatures are taken from the 2013 ASHRAE Fundamentals Handbook weather data for Chicago/Midway, IL, U.S.A. The peak dry bulb is 91.7F and the peak design wet bulb is 81.8F as given by monthly design wet bulb and mean coincident dry bulb at .4% in the Handbook.Two Design/Control ApproachesTwo design/control approaches will be studied; the first is based on the plant design as presented by the ASHRAE Journal of July 2011 thru June 2012 by Taylor, coupled with the control and design procedures defined by the (PNNL) study of Standard 90.1-2010. This approach will be named here as the ASHRAE Design. The second design/control approach is based on more conventional design/control practice and will be defined as the (min kW) Design.Plant design procedures as given by the ASHRAE Journal of July 2011 thru June 2012The ASHRAE Journal articles define a procedure for designing a central chilled water plant based on life cycle cost. This (min kW) Design model study will show that the ASHRAE designed plant requires
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significantly more kW demand than does a plant based on an (min kW) Design.
#ASHRAE Journal & Standard 90.1-2010Design & Control.
(Min kW) Design & Control.
(1) Infiltration of 6,811 CFM is called for byStd. 90.1-2010.
Pressurize the building to exfiltration of 3,378 CFM, no return fans.
(2) 70F perimeter stat set pt. will be aborted resulting in loss of stat control.
Control thermostats to minimize heating & cooling energy.
(3) Building return air path not controlled.
Control returns air to minimize heating & cooling energy.
(4) Installed fan powered supply air terminals.
Design the air supply system without fan powered terminals.
(5) Control air supply (55F) temperature to 60F when not at full cooling load, page 97 of Oct. 2013 ASHRAE Journal.
Control supply air to 55F design but may decrease to 50F to decrease fan kW.
(6) Table 5.2 of (PNNL) 90.1-2010 study limits heating air temperature to 20F above room temperature, (94F).
Perimeter heating air temperature of 110F.
(7) Table 5.11 of the (PNNL) study call for a TSP of 5.58 w.c.
Use same duct size as ASHRAE design, therefore less TSP for (min kW) Design.
(8) Design the plant based on ASHRAE Journal articles, “Optimizing Design & Control of Chilled
Design the plant with the objective of minimizing plant kW consistent with first cost control.
Water Plants”, July 2011-June 2012, by Taylor.
Table: Two designs compared
The Table briefly summarizes the major differences in the two designs.
REQUIRMENTS OF (SEE) MODELSThe requirements of a (SEE) Model include the follow:(1) The performance of the components of the system agrees with manufactures verified performance data, specifically the chiller, tower & air side equipment.(2) Energy into the system can be shown to equal the energy out of the system.(3) The model can produce a System Energy Equilibrium (SEE) Schematic.(4) The model can perform real time analysis of a building and input inefficiency to arrive at a duplication of the buildings real time performance. Chapter (1) will demonstrate these requirements for the (SEE) model of this Design Manual.
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CHAPTER (1) ASHRAE Design & (min kW Design) at PEAK Design Day ConditionsFigure 1-1 gives the assumed design day weather.The peak design temperatures are taken from the 2013 ASHRAE Fundamentals Handbook weather data for Chicago/Midway, IL, U.S.A. The peak dry bulb is 91.7F and the peak design wet bulb is 81.8F as given by monthly design wet bulb and mean coincident dry bulb at .4% in the Handbook.
76 75 7376 78 79 80 81 82 80 79 78
80.077.0 77.0 79.0
82.085.0
88.0 90.0 91.787.0
84.0 82.0
3035404550556065707580859095100
3035404550556065707580859095
100
% Clear Sky
AIR
TEM
Pera
ture
(F)
Air T
empe
ratu
re (F
)
TIME OF DAY
Peak weather day
(Temp)wet bulb (Temp)dry bulb
FIGURE 1-1: Assumed design day weather
Figure 1-2 illustrates the slight difference in the building load of the two designs. This chart can also be thought of as the energy into the building due to weather plus the light, plug, and people loads. The infiltration of the ASHRAE Design accounts for the slight increase.
80 62 6291
232
368 376 393 413
275
199
11388
67 6797
239
377 388 407428
286
207
119
050100150200250300350400450500
050
100150200250300350400450500
DRY BULB (F)
BUIL
DIN
G (t
on)
BUIL
DIN
G (t
on)
TIME OF DAYBLD ABS-ton)(ASHRAE & min kW Design)
(Bld)ABS-ton(min kW Design) (Bld)ABS-ton(ASHRAE Design)
FIGURE 1-2: Building design loadsThe point of Figure 1-2 is that the difference in the energy consumption of the two designs is due to design and control of the two systems; not a difference in the design of the basic building.Requirements of (SEE) ModelFour requirements of a (SEE) model are given above and will be illustrated here for the ASHRAE Design at peak summer design conditions.Figure 1-3 illustrates the energy into the ASHRAE Design; requirement (2). Note that at 4PM the energy into the system is about 2.7 times the energy into the building, Figure 1-1; illustrating the amount of energy required & consumed by the CCWS to condition the building.Figure 1-4 illustrates the energy out of the ASHRAE Design system.
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228.
8
199.
1
191.
8
241.
5
701.
6
998.
0
1039
.1
1092
.5
1146.8
814.
9
486.
5
330.
6
179.
032
4.5
643.
3
0
200
400
600
800
1000
1200
(TO
N)
TIME OF DAY
ENERGY INTO THE SYSTEM (ASHRAE Design) Peak Summer day
Total Energy In- (Ton) Plant kW energy in (Ton) Site kW energy in (Ton) Weather energy in (TON)
FIGURE 1-3: Energy in ASHRAE Design
-207 -178 -171-221
-614
-894
-935
-988
-104
2
-726
-445
-297
-4.7 -5.0 -4.3 -3.9 -10.8 -9.2 -9.2 -9.1 -9.0 -10.1 -5.8 -6.2-72.3 -90.5 -90.6 -90.8 -91.0 -74.9
-228
.8
-199
.1
-191
.8
-241
.5
-701
.6
-998
.0
-103
9.1
-109
2.5 -1146.8
-814
.9
-486
.5
-330
.6
-2.96 -2.70 -2.65 -3.11 -4.01 -4.40 -4.47 -4.57 -4.68 -4.13 -2.72 -2.94
-1200
-1000
-800
-600
-400
-200
0
200
(TO
N)
TIME OF DAY
ENERGY OUT OF THE SYSTEM (ASHRAE Design) Peak Summer day
Tower energy out-Ton Exhaust latent ton Exhaust sensible tonTotal energy out (Ton) Pump heat out(ton)
FIGURE 1-4: Energy out ASHRAE DesignFigure 1-5 & 1-6 illustrate the chiller & tower performance,(SEE Model requirement 1) as the evaporator load changes. At peak conditions the chiller kW/evaporator ton is (.61) and the tower range + approach is (20.7).
42%38% 36%
43%
56%
79% 84%
89% 95.0%
66%
79%
55%
117 106 101 120
313
441469
497531
369
221
154
1 1 1 1 2 2 2 2 2 2 1 1
0
100
200
300
400
500
600
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
NUMBER (#) CHILLERS ON
kW
CHIL
LER
% P
ower
Total EVAPORATOR Ton(ASHRAE Design) Chiller Performance Peak summer
(Chiller)% power Chiller-kW
FIGURE 1-5: Chiller performance
85.883.8
81.886.4
91.4
97.7 99.2 101.0 102.5
95.297.6
91.1
80.3 79.177.3
80.583.3
85.9 86.8 87.8 88.785.6 85.8
83.2
4.33 4.08 4.27 4.535.32
6.86 6.83 6.85 6.915.57
6.845.19
0
5
10
15
20
50
60
70
80
90
100
110
Tower range + approach (F)
Tow
er a
ppro
ach
(F)
Tow
er w
ater
tem
p. (F
)
Wet bulb (F)(ASHRAE Design) TOWER PERFORMANCE-Peak summer Wk day
(ewt)tower (F) (lwt)tower (F) Tower approach (F)
FIGURE 1-6: Tower performance
(SEE) Model requirement (3) (SEE) Schematic & (4) real time analysis will be demonstrated later in this manual; note a (SEE) Schematic is given in the Nomenclature.
Design day performance of the two designs:
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310 307 304 337
905
1,316 1,339 1,379 1,426
872
536412
506 487 481 536
1,129
1,611 1,653 1,707 1,770
1,122
765625
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
DRY BULB TEMPERATURE (F)
Syst
em (k
W)
Syst
em (k
W)
TIME of DAY
SYSTEM TOTAL (kW)
(min kW) Design (kW) ASHRAE Design (kW)
FIGURE 1-7: Systems total kW demandFigure 1-7 illustrates the difference in total system kW for the two designs at design day conditions.The charts below compare the two designs side by side.
348 410
532629
731 731
506 487 481 536
1,129
1,611 1,653 1,707 1,770
1,122
765625
0.00 0.00 0
500
1000
1500
2000
0
500
1000
1500
2000
DRY BULB (F)
(kW
)
kW
TIME OF DAYSYSTEM kW-All electric-498,600 sqft Bld-24 hr. ASHRAE Design
(AHU)Fan kW (plant)kW (Bld)kW (System)kW Duct heat kW FA Heat kW
Figure 1-8: ASHRAE design kW demand componentsFigures 1-8 & 1-9 illustrate the building kW is the same for both designs; the plant and air side system account for the greater values of the ASHRAE design.
BLD sq-ft = 498,600ALL ELECTRIC Peak day
Design 24hr BLD.24hr-kW= 10,096
(Fan)24hr-kW = 6,230(Duct)24hr-heat kW= 0
(FA)24hr-heat kW= 0Heat24hr-total kW= 0
Plant24hr-kW= 8,453SYST 24hr-kW = 24,779
(CCWS)24hr-kW= 14,683BLD.24hr-kW= 10,096
Total24hr-kW = 24,779
Table 1-1: ASHRAE design 24 hour at design day weatherTables 1-1 & 1-2 illustrate the difference in 24 hour energy consumption of the two designs at assumed design day weather conditions. The ASHRAE design consumes about 24% more energy at peak design day conditions; a significant increase due to what may appear as minor differences in the designs. Later chapters will explore in detail the differences in the two designs.
731 731
135 169450
525310 307 304 337
905
1,316 1,339 1,3791,426
872
536412
0 0 0
500
1000
1500
2000
0
500
1000
1500
2000
Dry bulb (F)
(kW
)
TIME OF DAY
SYSTEM kW -All electric 498,600 sqft Bld. (min kW) Design
(Bld)kW (AHU)Fan kW (plant)kW (System)kW Duct heat kW FA Heat kW
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Figure 1-9: (Min kW design) kW components at design day
BLD sq-ft = 498,600ALL ELECTRIC Peak design
Wk. Day 24hr BLD.24hr-kW= 10,096
(Fan)24hr-kW = 1,763(Duct)24hr-heat kW= 0
(FA)24hr-heat kW= 0Heat24hr-total kW= 0
Plant24hr-kW= 7,027SYST 24hr-kW = 18,887
(CCWS)24hr-kW= 8,791BLD.24hr-kW= 10,096
Total24hr-kW = 18,887
Table 1-2: (min kW design) 24 hours at design day weather
The following pages will consider performance at average summer, spring/fall and winter conditions with annual (bEQ) estimated.
Average summer performance
69 68 67 66 65 6568 70
73 72 71 70
74.0 72.0 70.067.0
71.076.0
79.0 81.0 83.0 81.078.0 76.0
3035404550556065707580859095100
3035404550556065707580859095
100
% Clear Sky
AIR
TEM
Pera
ture
(F)
Air T
empe
ratu
re (F
)
TIME OF DAY
Average summer weather day
(Temp)wet bulb (Temp)dry bulb
Figure 1-10: Assumed average summer weather dayFigure 1-10 illustrates the assumed weather conditions for an average summer day, based on ASHRAE Handbook data. Note the % clear sky is assumed as 80%.
295 298 319 314
703
1,059 1,1021,181 1,236
696
477379
477 465 459 486
912
1,3601,448 1,511
1,598
954
697585
0
200
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600
800
1000
1200
1400
1600
1800
2000
0
200
400
600
800
1000
1200
1400
1600
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DRY BULB TEMPERATURE (F)
Syst
em (k
W)
Syst
em (k
W)
TIME of DAY
SYSTEM TOTAL (kW)
(min kW) Design (kW) ASHRAE Design (kW)
Figure 1-11: Systems total kW demandFigure 1-11 illustrates the same pattern as Figure 1-7 but reduced values as expected. The following charts and tables compare the two designs.
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731 731
477 465 459 486
912
1,3601,448 1,511
1,598
954
697585
0
500
1000
1500
2000
0
500
1000
1500
2000
DRY BULB (F)
(kW
)
kW
TIME OF DAYSYSTEM kW-All electric-498,600 sqft Bld-24 hr. ASHRAE Design
(AHU)Fan kW (plant)kW (Bld)kW (System)kW Duct heat kW FA Heat kW
Figure 1-12: (ASHRAE design) component kW Figures 1-12 & 1-13 again illustrates the building kW is the same for both designs; the difference is in the response of the air side system and the plant to the building loads.
BLD sq-ft = 498,600ALL ELECTRIC Avg Summer
Design 24hr BLD.24hr-kW= 10,096
(Fan)24hr-kW = 9,080(Duct)24hr-heat kW= 0
(FA)24hr-heat kW= 0Heat24hr-total kW= 0
Plant24hr-kW= 5,723SYST 24hr-kW = 24,900
(CCWS)24hr-kW= 14,803BLD.24hr-kW= 10,096
Total24hr-kW = 24,900
Table 1-3: (ASHRAE design) 24 hours average summer weatherTables 1-3 & 1-5 illustrate the difference in 24 hour consumption and Tables 1-4 & 1-5 illustrate (bEQ) values based on 24 hour consumption.
ASHRAE Design kbtu/sqft-day
ALL ELECTRIC SYSTEM W/sqft (bEQ)dayBLD.24hr-W/sq ft-
= 20.25 0.069(Fan)24hr-W/sq ft- = 18.21 0.062Plant24hr-W/sq ft-= 11.48 0.039
(Heat)24hr-W/sq ft-= 0.00 0.000Syst Total24hr-W/sq ft-= 49.94 0.170
90 day (bEQ)= 15.34FUEL HEAT SYSTEM (bEQ)day
Bld,Fan,Plant24hr-W/sq ft-= 49.94 0.170Heat24hr-btu/sq ft= 0.00 0.000Syst Total24hr-= 0.17090 day (bEQ)= 15.34
Table 1-4: (ASHRAE design)(bEQ) estimateThe min kW Design and control concepts provide significantly better (bEQ) performance at average summer conditions and better performance as weather conditions cool.
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731 731
109 136218
369295 298 319 314
703
1,059 1,1021,181 1,236
696
477379
0
500
1000
1500
0
500
1000
1500
Dry bulb (F)(k
W)
TIME OF DAY
SYSTEM kW -All electric 498,600 sqft Bld. (min kW) Design
(Bld)kW (AHU)Fan kW (plant)kW (System)kW Duct heat kW FA Heat kW
Figure 1-13: (min kW design) kW components
BLD sq-ft = 498,600ALL ELECTRIC Avg Summer
Wk. Day 24hr BLD.24hr-kW= 10,096
(Fan)24hr-kW = 1,411(Duct)24hr-heat kW= 44
(FA)24hr-heat kW= 0Heat24hr-total kW= 44
Plant24hr-kW= 4,567SYST 24hr-kW = 16,119
(CCWS)24hr-kW= 6,022BLD.24hr-kW= 10,096
Total24hr-kW = 16,119
Table 1-5: (min kW design) 24 hours average summer weather
(Min kW) Wk. Day kbtu/sqft-day
ALL ELECTRIC SYSTEM W/sqft (bEQ)dayBLD.24hr-W/sq ft-
= 20.25 0.069(Fan)24hr-W/sq ft- = 2.83 0.010Plant24hr-W/sq ft-= 9.16 0.031
(Heat)24hr-W/sq ft-= 0.09 0.000Syst Total24hr-W/sq ft-= 32.33 0.110
90 day (bEQ)= 9.93FUEL HEAT SYSTEM (bEQ)dayBld,Fan,Plt24hr-W/sq ft-= 32.24 0.110
Heat24hr-btu/sq ft= 0.38 0.0004Syst Total24hr-= 0.11090 day (bEQ)= 9.94
Table 1-6: (min kW Design)(bEQ) estimate
Average Spring/Fall Weather
50 48 4642 43
47
5356 58 56 54 52
52.0 50.0 48.044.0 45.0
49.0
55.058.0 60.0 58.0 56.0 54.0
3035404550556065707580859095100
3035404550556065707580859095
100
% Clear Sky
AIR
TEM
Pera
ture
(F)
Air T
empe
ratu
re (F
)
TIME OF DAY
Spring/Fall weather day
(Temp)wet bulb (Temp)dry bulb
Figure 1-14: Average spring/fall weather dayFigure 1-14 illustrates the assumed average spring/fall weather and Figure 1-15 gives the difference in kW performance of the two designs.
436 463 485 463
727
961 933 964 968
648
454 456
1,051 1,095 1,142 1,146 1,107
1,3441,235
1,309 1,3141,220
1,132 1,110
0
200
400
600
800
1000
1200
1400
0
200
400
600
800
1000
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1400
DRY BULB TEMPERATURE (F)
Syst
em (k
W)
Syst
em (k
W)
TIME of DAY
SYSTEM TOTAL (kW)
(min kW) Design (kW) ASHRAE Design (kW)
Figure 1-15: Systems total kW demand
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371 394
133 188
731 731
1,051 1,095 1,142 1,146 1,107
1,3441,235
1,309 1,3141,220
1,132 1,110
659.9
0
500
1000
1500
0
500
1000
1500
DRY BULB (F)
(kW
)
kW
TIME OF DAYSYSTEM kW-All electric-498,600 sqft Bld-24 hr. ASHRAE Design
(AHU)Fan kW (plant)kW (Bld)kW (System)kW Duct heat kW FA Heat kW
Figure 1-16: (ASHRAE design) component kW Figures 1-16 & 1-17 illustrate the building kW is the same for both designs; the difference is in the response of the air side system and the plant.
BLD sq-ft = 498,600ALL ELECTRIC Spring/Fall
Design 24hr BLD.24hr-kW= 10,096
(Fan)24hr-kW = 6,587(Duct)24hr-heat kW= 8,654
(FA)24hr-heat kW= 0Heat24hr-total kW= 8,654
Plant24hr-kW= 3,074SYST 24hr-kW = 28,411
(CCWS)24hr-kW= 18,315BLD.24hr-kW= 10,096
Total24hr-kW = 28,411
Table 1-7: (ASHRAE design) 24 hours average spring/fall weatherTables 1-7 & 1-8 illustrate the difference in 24 hour consumption and Tables 1-9 & 1-10 illustrate (bEQ) based on 24 hour consumption.
ASHRAE Design kbtu/sqft-day
ALL ELECTRIC SYSTEM W/sqft (bEQ)dayBLD.24hr-W/sq ft-
= 20.25 0.069(Fan)24hr-W/sq ft- = 13.21 0.045Plant24hr-W/sq ft-= 6.17 0.021
(Heat)24hr-W/sq ft-= 17.36 0.059Syst Total24hr-W/sq ft-= 56.98 0.194
185 day (bEQ)= 35.98FUEL HEAT SYSTEM (bEQ)day
Bld,Fan,Plant24hr-W/sq ft-= 39.63 0.135Heat24hr-btu/sq ft= 74.04 0.074Syst Total24hr-= 0.209
185 day (bEQ)= 38.72
Table 1-9: (bEQ) estimate
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731 731
79 89
104 148
436 463 485 463
727
961 933 964968
648454 456
229.4
0
500
1000
1500
0
500
1000
1500
Dry bulb (F)(k
W)
TIME OF DAY
SYSTEM kW -All electric 498,600 sqft Bld. (min kW) Design
(Bld)kW (AHU)Fan kW (plant)kW (System)kW Duct heat kW FA Heat kW
Figure 1-17: (min kW design) kW components
BLD sq-ft = 498,600ALL ELECTRIC Spring/Fall
Wk. Day 24hr BLD.24hr-kW= 10,096
(Fan)24hr-kW = 1,034(Duct)24hr-heat kW= 2,494
(FA)24hr-heat kW= 0Heat24hr-total kW= 2,494
Plant24hr-kW= 2,290SYST 24hr-kW = 15,914
(CCWS)24hr-kW= 5,818BLD.24hr-kW= 10,096
Total24hr-kW = 15,914
Table 1-8: (min kW design) 24 hours average spring/fall weather
(Min kW) Wk. Day kbtu/sqft-day
ALL ELECTRIC SYSTEM W/sqft (bEQ)dayBLD.24hr-W/sq ft-
= 20.25 0.069(Fan)24hr-W/sq ft- = 2.07 0.007Plant24hr-W/sq ft-= 4.59 0.016
(Heat)24hr-W/sq ft-= 5.00 0.017Syst Total24hr-W/sq ft-= 31.92 0.109
185 day (bEQ)= 20.15FUEL HEAT SYSTEM (bEQ)dayBld,Fan,Plt24hr-W/sq ft-= 26.92 0.092
Heat24hr-btu/sq ft= 21.34 0.021Syst Total24hr-= 0.113
185 day (bEQ)= 20.94
Table 1-10: (bEQ) estimate
Average winter weather
2927 26
24 25
28
3234 35 34
3230
29.027.0 26.0
24.0 25.0
28.0
32.034.0 35.0 34.0
32.030.0
10
15
20
25
30
35
40
45
50
10
15
20
25
30
35
40
45
50
% Clear Sky
AIR
TEM
Pera
ture
(F)
Air T
empe
ratu
re (F
)
TIME OF DAY
Avg Winter weather day
(Temp)wet bulb (Temp)dry bulb
Figure 1-18: Assumed average winter weather dayFigure 1-18 illustrates the assumed average winter weather and Figure 1-19 gives the difference in kW performance of the two designs.
869 894 909 963
1,3511,507
1,403 1,343 1,399
1,113969 940
1,791 1,841 1,870 1,962
2,484
2,9732,792
2,6972,802
2,1001,903 1,886
0
500
1000
1500
2000
2500
3000
0
500
1000
1500
2000
2500
DRY BULB TEMPERATURE (F)
Syst
em (k
W)
Syst
em (k
W)
TIME of DAY
SYSTEM TOTAL (kW)
(min kW) Design (kW) ASHRAE Design (kW)
Figure 1-19: Systems total kW demand
Kirby Nelson PE Page 13
731 731
1,791 1,841 1,870 1,962
2,484
2,9732,792 2,697 2,802
2,1001,903 1,886
0
500
1000
1500
2000
2500
3000
0
500
1000
1500
2000
2500
3000
DRY BULB (F)
(kW
)
kW
TIME OF DAYSYSTEM kW-All electric-498,600 sqft Bld-24 hr. ASHRAE Design
(AHU)Fan kW (plant)kW (Bld)kW (System)kW Duct heat kW FA Heat kW
Figure 1-20: (ASHRAE design) component kW Figures 1-20 & 1-21 illustrate the building kW is the same for both designs; the difference is in the response of the air side system and the plant.
BLD sq-ft = 498,600ALL ELECTRIC Winter
Design 24hr BLD.24hr-kW= 10,096
(Fan)24hr-kW = 8,979(Duct)24hr-heat kW= 29,183
(FA)24hr-heat kW= 1,695Heat24hr-total kW= 30,878
Plant24hr-kW= 4,247SYST 24hr-kW = 54,200
(CCWS)24hr-kW= 44,104BLD.24hr-kW= 10,096
Total24hr-kW = 54,200
Table 1-11: (ASHRAE design) 24 hours average winter weatherTables 1-11 & 1-13 illustrate the difference in 24 hour consumption and Tables 1-12 & 1-14 illustrate (bEQ) based on 24 hour consumption.
ASHRAE Design kbtu/sqft-day
ALL ELECTRIC SYSTEM W/sqft (bEQ)dayBLD.24hr-W/sq ft-
= 20.25 0.069(Fan)24hr-W/sq ft- = 18.01 0.061Plant24hr-W/sq ft-= 8.52 0.029
(Heat)24hr-W/sq ft-= 61.93 0.211Syst Total24hr-W/sq ft-= 108.70 0.371
90 day (bEQ)= 33.39FUEL HEAT SYSTEM (bEQ)day
Bld,Fan,Plant24hr-W/sq ft-= 46.78 0.160Heat24hr-btu/sq ft= 264.20 0.264Syst Total24hr-= 0.42490 day (bEQ)= 38.15
Table 1-12: (bEQ) estimate
Kirby Nelson PE Page 14
731 731869 894 909 963
1,351
1,5071,403 1,343 1,399
1,113969 940
0
500
1000
1500
2000
0
500
1000
1500
2000
Dry bulb (F)(k
W)
TIME OF DAY
SYSTEM kW -All electric 498,600 sqft Bld. (min kW) Design
(Bld)kW (AHU)Fan kW (plant)kW (System)kW Duct heat kW FA Heat kW
Figure 1-21: (min kW design) kW components
BLD sq-ft = 498,600ALL ELECTRIC Winter
Wk. Day 24hr BLD.24hr-kW= 10,096
(Fan)24hr-kW = 1,274(Duct)24hr-heat kW= 12,962
(FA)24hr-heat kW= 1,695Heat24hr-total kW= 14,657
Plant24hr-kW= 1,292SYST 24hr-kW = 27,320
(CCWS)24hr-kW= 17,224BLD.24hr-kW= 10,096
Total24hr-kW = 27,320
Table 1-13: (min kW design) 24 hours average winter weather
(Min kW) Wk. Day kbtu/sqft-day
ALL ELECTRIC SYSTEM W/sqft (bEQ)dayBLD.24hr-W/sq ft-
= 20.25 0.069(Fan)24hr-W/sq ft- = 2.55 0.009Plant24hr-W/sq ft-= 2.59 0.009
(Heat)24hr-W/sq ft-= 29.40 0.100Syst Total24hr-W/sq ft-= 54.79 0.187
90 day (bEQ)= 16.83FUEL HEAT SYSTEM (bEQ)dayBld,Fan,Plt24hr-W/sq ft-= 25.40 0.087
Heat24hr-btu/sq ft= 125.42 0.125Syst Total24hr-= 0.21290 day (bEQ)= 19.09
Table 1-14: (bEQ) estimate
CONCLUSIONS of CHAPTER 1The purpose of this chapter (1) is to give an indication of the magnitude of the difference in energy consumption that can occur with seemingly slight differences in system design and control.Table 1-15 illustrates estimated (bEQ) values based on 3 months of average summer weather, 6 months of average spring/fall weather and 3 months of average winter weather.
All Elect. Building
ASHRAE design (bEQ)
Min kW design (bEQ)
Summer-3m 15.34 9.93spring/fall-6m 35.98 20.15Winter-3m 33.39 16.83Est. annual (bEQ)
84.71 46.91
TABLE 1-15: Chicago (bEQ) Estimates
Table 1-15 illustrates that the ASHRAE Design becomes less efficient, as compared to the min kW Design, as the weather becomes colder. The winter ASHRAE Design (bEQ) is twice the value of the (min kW Design). The difference is primarily due to the air side design & control of the perimeter heating; to be discussed in detail in coming chapters.
The detail differences in the design and control of the two designs form the basis of the remainder of this Design/Control Manual.
Kirby Nelson PE Page 15
Table 1-16, presents the Houston (bEQ) for comparison. Houston (bEQ) is based on 5 months of average summer weather, 4 months of average spring/fall weather and 3 months of average winter weather.All Elect. Building
ASHRAE design (bEQ)
Min kW design (bEQ)
Summer -5m 24.37 18.29spring/fall-4m 25.62 16.02Winter -3m 16.96 9.36Est. annual (bEQ)
66.95 43.67
Table 1-16: Houston (bEQ) Estimate
System Nomenclature Each of the more than 100 components of the system will be defined.The (PNNL) study defines the large office building as given by Figure N-1, a 13 story office with 498,600 square feet of air conditioned space.
FIGURE N-1: Building description The (PNNL) study can be viewed at;http://www.energycodes.gov/sites/default/files/documents/BECP_Energy_Cost_Savings_STD2010_May2011_v00.pdf orhttp://www.energycodes.gov/achieving-30-goal-energy-and-cost-savings-analysis-ashrae-standard-901-2010
BLD ft2 = %clear sky = InfilLat-ton =
# floors = Tdry-bulb = Infil-CFM = <Roof ft2 = Twet-bulb= Infilsen-ton =
N/S wall ft2 = WallNtrans ton=E/W wall ft2 = WallStrans ton=
Wall % glass= WallEtrans ton=Glass U = WallWtranston= WallTot trans ton =
Wall U = GlassN trans ton =Glass SHGC = GlassS trans ton =
Wall emitt = GlassE-trans ton =RoofTrans ton = GlassW-trans ton = GlassTot-trans-ton=Roofsky lite ton = GlassN-solar-ton =
Peopleton = kW GlassS-solar-ton =plugton = GlassE-solar ton =Lightton= GlassW-solar ton = GlassTot-solar-ton =
(int-cfm)to-per-ret= BLD kW= (int cfm)per-ton = >Total Bldint-ton = AHU kW= Tot Bldper-sen-ton = v
Tstat-int= SITE kW = Tstat-per = return(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= air
BUILDING NOMENCLATURE:Building structure;
Kirby Nelson PE Page 16
BLD ft2 = air conditioned space# Floors = number of building floorsRoof ft2 = roof square feetN/S wall ft2 =north/south wall square feetE/W wall ft2 =east/west wall square feetWall % glass = percent of each wall that is glassGlass U = glass heat transfer coefficientWall U = wall heat transfer coefficientGlass SHGC = glass solar heat gain coefficientWall emit = wall solar indexBuilding interior space;Rooftrans-ton =transmission through roof (ton)Roofsky-lite-ton =sky lite load (ton)Peopleton = cooling load due to people (ton)Plugton = cooling load due to plug kWPlugtkW = kW demand due to plug loadsLightton = cooling load due to lights (ton)LightkW = kW demand due to lights(int-cfm)to-per-return = CFM of interior supply air that returns to perimeter of buildingTotal Bldint-ton = total building interior load (ton)Tstat-int = interior stat set temperature (F)Bldint-air-ton = supply air ton to offset interior loadBuilding perimeter space;%clear sky = percent solar that hits buildingTdry bulb = outside dry bulb temperature (F)Twet bulb = outside wet bulb temperature (F)Infillat-ton = latent load due to air infiltration (ton)InfilCFM = air infiltration CFMInfilsen-ton = sensible load due to air infiltration (ton)Walln trans ton = north wall transmission (ton)Walls trans ton = south wall transmission (ton)WallE trans ton = east wall transmission (ton)Wallw trans ton = west wall transmission (ton)Walltot-trans-ton = total wall transmission (ton)GlassN-trans-ton = north wall glass transmission (ton)GlassS-trans-ton = south wall glass transmission (ton)GlassE-trans-ton = east wall glass transmission (ton)GlassW trans-ton = west wall glass transmission (ton)Glasstot-trans-ton = total transmission thru glass (ton) GlassN-solar-ton = north glass solar load (ton)GlassS-solar-ton = south glass solar load (ton)GlassE-solar-ton = east glass solar load (ton)GlassW-solar-ton = west glass solar load (ton)Glasstot-solar-ton = total glass solar load (ton)(int cfm)per-ton = effect of interior CFM to wall (ton)
Total Bldper-sen-ton total perimeter sensible load (ton)Tstat-per = perimeter stat set temperature (F)Bldper-air-ton = supply air ton to offset perimeter load
Tair supply int= ASHRAE Design Tair supply per=
^ ABS Bld Ton = ^Ton kW Ton kW V
(fan)int-ter= (fan)per-ter=Theat-air= (D)heat =
Treheat air =(D)reheat =
(D)int-air-ton= Interior (D)per-air-ton= PeriTair coils = duct Tair coils= duct
(D)int-CFM= ^ (D)per-CFM= ^>>>(Coil)sen-ton= ^ (coil)gpm= ^
(coil)cap-ton= UAdesign=(coil)H2O-ft/sec= COIL UA=(coil)des-ft/sec= (one coil)ton=
LMTD= (H)coil= V(COIL)L+s-ton= ^ ^ ^ (H)coil-des=
<<<< Tair VAV= TBLD-AR =(FAN)VAV-CFM= (Air)ret-CFM = Return(FAN)ton-VAV= (FAN)ret-kW= Fan(FAN)kW-VAV= (FAN)ret-ton= V
^ (Air)ret-ton =26 F.A.Inlet ^ Tar-to-VAV =
statFA= 26 VAV FANS VAVret-ton = TFA to VAV = > Tret+FA = InfilVAV-Lat-ton =
>(FA)sen-ton = > (dh) = < VAVret-CFM = <> (FA)CFM= > Efan-VSD= InfilCFM-ton = V
> (FA)Lat-ton=(FA)kW= ExLat-ton =
ExCFM =temp pink TEx =gpm orange Exsen-ton = V
FIGURE 2A Air handler system AIR HANDLER DUCT SYSTEM NOMENCLATURE
(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= airTair supply int= ASHRAE Design Tair supply per=
^ ABS Bld Ton = ^Ton kW Ton kW V
(fan)int-ter= (fan)per-ter=Theat-air= (D)heat =
Treheat air =(D)reheat =
(D)int-air-ton= Interior (D)per-air-ton= PeriTair coils = duct Tair coils= duct
(D)int-CFM= ^ (D)per-CFM= ^
Duct system nomenclatureTair supply int = temperature air supply to interior (F)(fan)int-ter-kW = kW demand of interior terminal fans(fan)int-ter-ton = load due to interior terminal fans kW (D)int-air-ton = cooling (ton) to interior ductTair coils = supply air temperature off coils to duct(D)int-CFM = supply air CFM to interior duct
Kirby Nelson PE Page 17
(ABS Bld Ton) = absolute building load on (CCWS)Tair supply per = temperature air supply perimeter (F)(fan)per-ter-kW = kW demand perimeter terminal fans(fan)per-ter-ton = load due to perimeter terminal fansTheat-air = temp supply air before terminal fan heat(D)heat-kW = kW heat to perimeter supply air(D)heat-ton = (ton) heat to perimeter supply airTreheat air = temp(F) perimeter supply air after reheat (D)reheat-kW = kW reheat to perimeter supply air(D)reheat-ton = (ton) reheat to perimeter supply air(D)per-air-ton = cooling (ton) to perimeter duct Tair coils = supply air temperature off coils to duct(D)per-CFM = supply air CFM to perimeter ductCOIL NOMENCLATURE(coil)sen-ton = sensible load on all coils (ton)(coil)cap-ton = LMTD * UA = capacity (ton) one coil(coil)H2O-ft/sec = water velocity thru coil (ft/sec)(coil)design-ft/sec = coil design water velocity (ft/sec)LMTD = coil log mean temperature difference (F)(coil)L+s-ton = latent + sensible load on all coils (ton)(coil)gpm = water flow (gpm) thru one coilUAdesign = coil UA design valueUA = coil heat transfer coefficient * coil area. UA varies as a function water velocity (coil)gpm thru the coil, therefore as the (coil)gpm decreases the coil capacity decreases.
(D)int-CFM= ^ (D)per-CFM= ^>>>(Coil)sen-ton= ^ (coil)gpm= ^
(coil)cap-ton= UAdesign=(coil)H2O-ft/sec= COIL UA=(coil)des-ft/sec= (one coil)ton=
LMTD= (H)coil= V(COIL)L+s-ton= ^ ^ ^ (H)coil-des=
<<<< Tair VAV= TBLD-AR = Coils(one coil)ton = load (ton) on one coil(H)coil = air pressure drop thru coil (ft)(H)coil-design = design air pressure drop (ft)
(COIL)L+s-ton= ^ ^ ^ (H)coil-des=<<<< Tair VAV= TBLD-AR =
(FAN)VAV-CFM= (Air)ret-CFM = Return(FAN)ton-VAV= (FAN)ret-kW= Fan(FAN)kW-VAV= (FAN)ret-ton= V
^ (Air)ret-ton =26 F.A.Inlet ^ Tar-to-VAV =
statFA= 26 VAV FANS VAVret-ton = TFA to VAV = > Tret+FA = InfilVAV-Lat-ton =
>(FA)sen-ton = > (dh) = < VAVret-CFM = <> (FA)CFM= > Efan-VSD= InfilCFM-ton = V
> (FA)Lat-ton=(FA)kW= ExLat-ton =
ExCFM =temp pink TEx =gpm orange Exsen-ton = V
VAV FAN SYSTEM NOMENCLATUREFresh air nomenclature:statFA = fresh air freeze stat set temperature (F)TFA to VAV = temperature of fresh air to VAV fan(FA)sen-ton = fresh air sensible load (ton)(FA)CFM = CFM fresh air to VAV fan inlet(FA)Lat-ton = fresh air latent load (ton)(FA)kW = heat kW to statFA set temperatureAir return nomenclature: TBLD-AR = return air temp (F) before return fan(Air)ret-CFM = CFM air return from building(FAN)ret-kW = return fans total kW(FAN)ret-ton = cooling load (ton) due to (FAN)ret-kW
(Air)ret-ton = return air (ton) before return fansTAR to VAV = TBLD-AR + delta T due to return fans kWVAVret-ton = return (ton) to VAV fans inletInfilVAV-Lat-ton = infiltration latent (ton) to VAV fansVAVret-CFM = return CFM to VAV fans inletInfilCFM-ton = load (ton) due to infiltration CFMExhaust air nomenclatureExLat-ton = latent load (ton) exhaustedExCFM = CFM of exhaust airTEx = temperature of exhaust air Exsen-ton = sensible load (ton) exhaustedVAV Fans nomenclatureTair-VAV = temp. air to coils after VAV fan heat(FAN)VAV-CFM = CFM air thru coils(FAN)ton-VAV = load (ton) due to VAV fan kW(FAN)kW-VAV = total VAV fan kW demandTret+FA = return and fresh air mix temperature (F)(dh) = VAV air static pressure (ft)Efan-VSD = VAV fans efficiency
Kirby Nelson PE Page 18
AIR SIDE SYSTEM PLUS BUILDING BLD ft2 = %clear sky = InfilLat-ton =
# floors = Tdry-bulb = Infil-CFM = <Roof ft2 = Twet-bulb= Infilsen-ton =
N/S wall ft2 = WallNtrans ton=E/W wall ft2 = WallStrans ton=
Wall % glass= WallEtrans ton=Glass U = WallWtranston= WallTot trans ton =
Wall U = GlassN trans ton =Glass SHGC = GlassS trans ton =
Wall emitt = GlassE-trans ton =RoofTrans ton = GlassW-trans ton = GlassTot-trans-ton=Roofsky lite ton = GlassN-solar-ton =
Peopleton = kW GlassS-solar-ton =plugton = GlassE-solar ton =Lightton= GlassW-solar ton = GlassTot-solar-ton =
(int-cfm)to-per-ret= BLD kW= (int cfm)per-ton = >Total Bldint-ton = AHU kW= Tot Bldper-sen-ton = v
Tstat-int= SITE kW = Tstat-per = return(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= air
Tair supply int= ASHRAE Design Tair supply per=
^ ABS Bld Ton = ^Ton kW Ton kW V
(fan)int-ter= (fan)per-ter=Theat-air= (D)heat =
Treheat air =(D)reheat =
(D)int-air-ton= Interior (D)per-air-ton= PeriTair coils = duct Tair coils= duct
(D)int-CFM= ^ (D)per-CFM= ^>>>(Coil)sen-ton= ^ (coil)gpm= ^
(coil)cap-ton= UAdesign=(coil)H2O-ft/sec= COIL UA=(coil)des-ft/sec= (one coil)ton=
LMTD= (H)coil= V(COIL)L+s-ton= ^ ^ ^ (H)coil-des=
<<<< Tair VAV= TBLD-AR =(FAN)VAV-CFM= (Air)ret-CFM = Return(FAN)ton-VAV= (FAN)ret-kW= Fan(FAN)kW-VAV= (FAN)ret-ton= V
^ (Air)ret-ton =26 F.A.Inlet ^ Tar-to-VAV =
statFA= 26 VAV FANS VAVret-ton = TFA to VAV = > Tret+FA = InfilVAV-Lat-ton =
>(FA)sen-ton = > (dh) = < VAVret-CFM = <> (FA)CFM= > Efan-VSD= InfilCFM-ton = V
> (FA)Lat-ton=(FA)kW= ExLat-ton =
ExCFM =temp pink TEx =gpm orange Exsen-ton = V
Kirby Nelson PE Page 19
Condenser(cond)ton= Pipesize-in = (H)T-pipe= Tower
TCR= > gpmT= > (ewt)T= tfan-kW=TCR-app= (H)T-total= (H)T-static = Tfan-kW=
(COND)ton= PT-heat = Trange= tfan-%=(H)cond= < pT-kW= < (lwt)T = tton-ex=
(cond)ft/sec= EfTpump= Tapproach = T#=Ptower # = T-Ton-ex=
Trg+app =Compressor ASHRAE Design
(chiller)kW= Chicago 90.1-2010(chiller)lift= Large Office(chiller)%= Peak day Design 4PM(chiller)#= Weather %clear sky =
(CHILLER)kW= conditions Tdry bulb =(chiller)kW/ton= Twet bulb =Plant kW =
> Evaporator(evap)ton=
TER=TER-app=
^ EVAPton=(H)evap=
(evap)ft/sec=(evap)des-ft/sec=
^ Vgpmevap= Psec-heat-ton =
(lwt)evap = > Psec-kW= > (ewt)coil=(H)pri-total= v Efdes-sec-p =
^ (H)pri-pipe= Tbp= Efsec-pump =(H)pri-fitings= gpmbp= (H)sec= PLANTton =(Ef)c-pump= (H)pri-bp= (H)sec-pipe=Pc-heat-ton= v (H)sec-bp= Pipesize-in =
^ < pc-kW= (ewt)evap = < (gpm)sec= < (lwt)coil=Pchiller-# =
CENTRAL PLANT Nomenclature will be defined by addressing each component of the plant.Primary/secondary pumping nomenclaturegpmevap = total gpm flow thru evaporators(H)pri-total = total primary pump head (ft) = (H)pri-pipe + (H)pri-fittings + (H)pri-bp + (H)evap
(H)pri-pipe = primary pump head due to piping (ft)(H)pri-fittings = primary head due to pump & fitting (ft)(Ef)c-pump = efficiency of chiller pumpPc-heat-ton = chiller pump heat to atmosphere (ton)Pc-kW = one chiller pump kW demand (kW)Pchiller-# = number chiller pumps operating(lwt)evap = temperature water leaving evaporator (F)Tbp = temperature of water in bypass (F)gpmbp = gpm water flow in bypass(H)pri-bp = head if chiller pump flow in bypass (ft)(ewt)evap = temp water entering evaporator (F)
Psec-heat-ton = secondary pump energy not into system (ton), goes to atmospherePsec-kW = kW demand of secondary pumpsEfdes-sec-p = design efficiency of secondary pumpingEfsec-pump = efficiency of secondary pumping(H)sec = secondary pump head (ft) = (H)sec-pipe + (H)sec-
bp + (H)coil + (H)valve
(H)sec-pipe = secondary pump head due to pipe (ft)(H)sec-bp = head in bypass if gpmsec > gpmevap
gpmsec = water gpm flow in secondary loop(ewt)coil = water temperature entering coil (F)Plantton = load (ton) from air side to plantPipesize-in = secondary pipe size (inches)(lwt)coil = temperature of water leaving coil (F)Condenser nomenclature:(cond)ton = load (ton) on one condenserTCR = temperature of condenser refrigerant (F)TCR-app = refrigerant approach temperature (F)(COND)ton = total load (ton) on all condensers(H)cond = tower pump head thru condenser (ft)(cond)ft/sec = tower water flow thru condenser Compressor:(chiller)kW = each chiller kW demand(chiller)lift = (TCR – TER) = chiller lift (F)(chiller)% = percent chiller motor is loaded(chiller)# = number chillers operating(CHILLER)kW = total plant chiller kW(chiller)kW/ton = chiller kW per evaporator tonEvaporator(evap)ton = load (ton) on one evaporatorTER = evaporator refrigerant temp (F)TER-app = evaporator refrigerant approach (F)EVAPton = total evaporator loads (ton)(H)evap = pump head thru evaporator (ft)(evap)ft/sec = velocity water flow thru evaporator(evap)des-ft/sec = evaporator design flow velocityTower piping nomenclaturePipesize-in = tower pipe size (inches)gpmT = each tower water flow (gpm)(H)T-total = total tower pump head (ft)PT-heat = pump heat to atmosphere (ton)PT-kW = each tower pump kW demandEfT-pump = tower pump efficiencyPtower # = number of tower pumps(H)T-pipe = total tower pump head (ft)
Kirby Nelson PE Page 20
Kirby Nelson PE Page 21
Tower piping nomenclature cont.(ewt)T = tower entering water temperature (F)(H)T-static = tower height static head (ft)Trange = tower range (F)= (ewt)T – (lwt)T
(lwt)T = tower leaving water temperature (F)Tapproach = (lwt)T – (Twet-bulb)Tower nomenclature
tfan-kW = kW demand of one tower fanTfan-kW = tower fan kW of fans on
tfan-% = percent tower fan speedtton-ex = ton exhaust by one tower
T# = number of towers onTton-ex = ton exhaust by all towers onTrg+app = tower range + approach (F)SYSTEM PERFORMANCE The performance indices of the following Tables are self-explanatory. A complete schematic will be shown below.
Chicago 4PM All ElectricFuel HeatPerformance 4PM Design kW THERM
chillerkW/evapton= BLD.kW=(plant)kW/site ton= (Fan)kW =CCWSkW/bld ton= Ductheat=WeatherEin-ton = (FA)heat=(Site)kW-Ein-ton = Heat total =PlantkW-Ein-ton = PlantkW=
Total Ein-ton = SystkW =Pumptot-heat-ton =
AHU ExLat-ton = BLD.kW=AHU Exsen-ton = CCWSkW =Tower Tton-Ex = SystkW =Total Eout-ton =
Performance table at given hour
BLD sq-ft =ALL ELECTRIC Peak day
Design 24hr BLD.24hr-kW=
(Fan)24hr-kW =(Duct)24hr-heat kW=
(FA)24hr-heat kW=Heat24hr-total kW=
Plant24hr-kW=SYST 24hr-kW =
(CCWS)24hr-kW=BLD.24hr-kW=
Total24hr-kW =
24 Hour performance, all-electric
ASHRAE DesignBLD sq ft =
Fuel heat Peak dayDesign 24hr ThermBLD.24hr-kW=
(Fan)24hr-kW =(Duct)24hr-heat therm=
(FA)24hr-heat therm=Heat24hr-total therm=
Plant24hr-kW=SYST 24hr-kW =
24 Hour performance, heat with fuel
Weather24h-Ein-ton= SITE24h-kW-Ein-ton = Plant24h-kW-Ein-ton =Total24h-Ein-ton =Pump24hr-heat-ton =
AHU Ex24hr-Lat-ton =AHU Ex24hr-sen-ton =
Tower24hr-ton-Ex =Total E24hr-out-ton =
ASHRAE Design
24 Hour Energy in = Energy out
ASHRAE Design kbtu/sqft-day
ALL ELECTRIC SYSTEM W/sqft (bEQ)dayBLD.24hr-W/sq ft-
=(Fan)24hr-W/sq ft- =Plant24hr-W/sq ft-=
(Heat)24hr-W/sq ft-=Syst Total24hr-W/sq ft-=
90 day (bEQ)=FUEL HEAT SYSTEM (bEQ)day
Bld,Fan,Plant24hr-W/sq ft-= 49.70Heat24hr-btu/sq ft= 0.00
Syst Total24hr-=90 day (bEQ)=
(bEQ) estimate
Next the full system energy equilibrium (SEE) schematic.
Kirby Nelson PE Page 22
BLD ft2 = %clear sky = InfilLat-ton =
Condenser # floors = Tdry-bulb = Infil-CFM = <(cond)ton= Pipesize-in = (H)T-pipe= Tower Roof ft2 = Twet-bulb= Infilsen-ton =
TCR= > gpmT= > (ewt)T= tfan-kW= N/S wall ft2 = WallNtrans ton=TCR-app= (H)T-total= (H)T-static = Tfan-kW= E/W wall ft2 = WallStrans ton=
(COND)ton= PT-heat = Trange= tfan-%= Wall % glass= WallEtrans ton=(H)cond= < pT-kW= < (lwt)T = tton-ex= Glass U = WallWtranston= WallTot trans ton =
(cond)ft/sec= EfTpump= Tapproach = T#= Wall U = GlassN trans ton =Ptower # = T-Ton-ex= Glass SHGC = GlassS trans ton =
Trg+app = Wall emitt = GlassE-trans ton =Compressor ASHRAE Design RoofTrans ton = GlassW-trans ton = GlassTot-trans-ton=
(chiller)kW= Chicago 90.1-2010 Roofsky lite ton = GlassN-solar-ton =(chiller)lift= Large Office Peopleton = kW GlassS-solar-ton =(chiller)%= Peak day Design 4PM plugton = GlassE-solar ton =(chiller)#= Weather %clear sky = Lightton= GlassW-solar ton = GlassTot-solar-ton =
(CHILLER)kW= conditions Tdry bulb = (int-cfm)to-per-ret= BLD kW= (int cfm)per-ton = >(chiller)kW/ton= Twet bulb = Total Bldint-ton = AHU kW= Tot Bldper-sen-ton = vPlant kW = Tstat-int= SITE kW = Tstat-per = return
(Bld)int.air-ton= ^ Design 4PM ^ (Bld)per.air-ton= airTair supply int= ASHRAE Design Tair supply per=
^ ABS Bld Ton = ^ > Evaporator Ton kW Ton kW V
(evap)ton= (fan)int-ter= (fan)per-ter=TER= Theat-air=
TER-app= (D)heat = ^ EVAPton= Treheat air =
(H)evap= (D)reheat =
(evap)ft/sec=(evap)des-ft/sec= (D)int-air-ton= Interior (D)per-air-ton= Peri
^ V Tair coils = duct Tair coils= ductgpmevap= Psec-heat-ton = (D)int-CFM= ^ (D)per-CFM= ^
(lwt)evap = > Psec-kW= > (ewt)coil= >>>(Coil)sen-ton= ^ (coil)gpm= ^(H)pri-total= v Efdes-sec-p = (coil)cap-ton= UAdesign=
^ (H)pri-pipe= Tbp= Efsec-pump = (coil)H2O-ft/sec= COIL UA=(H)pri-fitings= gpmbp= (H)sec= PLANTton = (coil)des-ft/sec= (one coil)ton=(Ef)c-pump= (H)pri-bp= (H)sec-pipe= LMTD= (H)coil= VPc-heat-ton= v (H)sec-bp= Pipesize-in = (COIL)L+s-ton= ^ ^ ^ (H)coil-des=
^ < pc-kW= (ewt)evap = < (gpm)sec= < (lwt)coil= <<<< Tair VAV= TBLD-AR =Pchiller-# = (FAN)VAV-CFM= (Air)ret-CFM = Return
Chicago 4PM All ElectricFuel Heat (FAN)ton-VAV= (FAN)ret-kW= FanPerformance 4PM Design kW THERM (FAN)kW-VAV= (FAN)ret-ton= V
chillerkW/evapton= BLD.kW= ^ (Air)ret-ton =(plant)kW/site ton= (Fan)kW = 26 F.A.Inlet ^ Tar-to-VAV =CCWSkW/bld ton= Ductheat= statFA= 26 VAV FANS VAVret-ton = WeatherEin-ton = (FA)heat= TFA to VAV = > Tret+FA = InfilVAV-Lat-ton =(Site)kW-Ein-ton = Heat total = Tdry bulb = >(FA)sen-ton = > (dh) = < VAVret-CFM = <PlantkW-Ein-ton = PlantkW= Fresh air > >>> > (FA)CFM= > Efan-VSD= InfilCFM-ton = V
Total Ein-ton = SystkW = Twet bulb = > (FA)Lat-ton=Pumptot-heat-ton = (FA)kW= ExLat-ton =
AHU ExLat-ton = BLD.kW= SEE SCHEMATIC ExCFM =AHU Exsen-ton = CCWSkW = ton blue water temp pink TEx =Tower Tton-Ex = SystkW = air cfm purplewater gpm orange Exsen-ton = V Total Eout-ton = air temp green kW red
System Energy Equilibrium (SEE) Schematic
Kirby Nelson PE Page 23