Central Chilled Water Systems
(CCWS)
Design/Control Manual
Of
CHICAGO LARGE OFFICE
ASHRAE DESIGN
&
(min kW) DESIGN
Kirby Nelson PE
3/23/2016
Kirby Nelson PE
Page 1
Contents: Chicago Design Manual
Preface
Introduction
CHAPTER (1) ASHRAE Design & (min kW Design)
-Peak Design Day Performance
-Average Summer Day Performance
-Average Spring/Fall Day Performance
-Average Winter Day Performance
NOMENCLATURE
Detail analysis will be added.
Kirby Nelson PE
Page 2
PREFACE
DOE 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) Model
System 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.
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/
Kirby Nelson experience
The following is a brief history of Kirby’s experience
in System Energy Equilibrium (SEE) Modeling and
analysis.
Kirby Nelson PE
Page 3
INTRODUCTION
Several 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;
Kirby Nelson PE
http://www.energycodes.gov/sites/default/files/
documents/BECP_Energy_Cost_Savings_STD2010
_May2011_v00.pdf or
http://www.energycodes.gov/achieving-30-goalenergy-and-cost-savings-analysis-ashraestandard-901-2010
BUILDING DEFINED
The (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 Approaches
Two 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 2012
The 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
significantly more kW demand than does a plant
based on an (min kW) Design.
Page 4
#
(1)
(2)
(3)
ASHRAE Journal &
(Min kW) Design &
Standard 90.1-2010 Control.
Design & Control.
Infiltration of 6,811
CFM is called for by
Std. 90.1-2010.
70F perimeter stat
set pt. will be aborted
resulting in loss of
stat control.
Building return air
path not controlled.
(4)
Installed fan powered
supply air terminals.
(5)
Control air supply
(55F) temperature to
60F when not at full
cooling load, page 97
of Oct. 2013 ASHRAE
Journal.
Table 5.2 of (PNNL)
90.1-2010 study
limits heating air
temperature to 20F
above room
temperature, (94F).
Table 5.11 of the
(PNNL) study call for
a TSP of 5.58 w.c.
(6)
(7)
(8)
Design the plant
based on ASHRAE
Journal articles,
“Optimizing Design &
Control of Chilled
Water Plants”, July
2011-June 2012, by
Taylor.
Pressurize the building
to exfiltration of 3,378
CFM, no return fans.
Control thermostats to
minimize heating &
cooling energy.
Control returns air to
minimize heating &
cooling energy.
Design the air supply
system without fan
powered terminals.
Control supply air to 55F
design but may
decrease to 50F to
decrease fan kW.
The Table briefly summarizes the major differences
in the two designs.
REQUIRMENTS OF (SEE) MODELS
The 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.
Perimeter heating air
temperature of 110F.
Use same duct size as
ASHRAE design,
therefore less TSP for
(min kW) Design.
Design the plant with
the objective of
minimizing plant kW
consistent with first cost
control.
Table: Two designs compared
Kirby Nelson PE
Page 5
CHAPTER (1) ASHRAE Design & (min kW Design) at
PEAK Design Day Conditions
Figure 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.
(Temp)dry bulb
% Clear Sky
100
65
60
60
55
55
50
50
45
45
40
40
35
35
30
30
Total Energy In- (Ton)
Site kW energy in (Ton)
1200
Weather energy in (TON)
1146.8
1000
800
(TON)
TIME OF DAY
Peak weather day
FIGURE 1-1: Assumed design day
weather
600
400
179.0
200
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.
(Bld)ABS-ton(min kW Design)
Plant kW energy in (Ton)
330.6
70
65
486.5
75
814.9
78
643.3
79
324.5
80
80
0
TIME OF DAY
ENERGY INTO THE SYSTEM (ASHRAE Design) Peak Summer day
FIGURE 1-3: Energy in ASHRAE Design
(Bld)ABS-ton(ASHRAE Design)
Tower energy out-Ton
Exhaust latent ton
Total energy out (Ton)
Pump heat out(ton)
Exhaust sensible ton
200
DRY BULB (F)
-2.96
-2.70
-2.65
-3.11
-4.01
-4.40
-4.47
-4.57
-4.68
-4.13
-2.72
-2.94
-4.7
-207
-5.0
-178
-4.3
-171
-3.9
-221
-10.8
-72.3
-9.2
-90.5
-9.2
-90.6
-9.1
-90.8
-9.0
-91.0
-10.1
-74.9
-5.8
-6.2
-814.9
80
1092.5
79
-988
78
85
-1042
73
76
82
1039.1
75
81
90
82.0
998.0
70
76
77.0
84.0
701.6
75
77.0
95
87.0
241.5
Air Temperature (F)
80
79.0
85.0
91.7
191.8
80.0
82.0
90.0
-191.8
85
88.0
-199.1
90
AIR TEMPerature (F)
95
199.1
100
228.8
(Temp)wet bulb
design and control of the two systems; not a
difference in the design of the basic building.
Requirements of (SEE) Model
Four 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.
200
232
88
80
67
67
62
62
97
199
119
113
91
150
100
50
0
TIME OF DAY
BLD ABS-ton)(ASHRAE & min kW Design)
FIGURE 1-2: Building design loads
The point of Figure 1-2 is that the difference in the
energy consumption of the two designs is due to
Kirby Nelson PE
-800
-1200
-297
-330.6
-445
-1000
-486.5
-726
-600
-1092.5
250
207
-400
-935
300
-894
350
286
-1039.1
0
400
413
-998.0
50
393
275
200
100
368
376
239
250
150
388
-200
-614
300
377
450
(TON)
350
428
BUILDING (ton)
BUILDING (ton)
400
407
-701.6
500
450
-241.5
500
-228.8
0
-1146.8
TIME OF DAY
ENERGY OUT OF THE SYSTEM (ASHRAE Design) Peak Summer day
FIGURE 1-4: Energy out ASHRAE
Design
Page 6
Figure 1-5 & 1-6 illustrate the chiller & tower
Design day performance of the two designs:
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).
(min kW) Design (kW)
ASHRAE Design (kW)
DRY BULB TEMPERATURE (F)
2400
2400
2200
Chiller-kW
2200
2000
1,707
1,611 1,653
1800
1
1
1
NUMBER (#) CHILLERS ON
2
2
2
2
2
2
1
1
100%
600
89%
90%
79%
CHILLER % Power
70%
56%
60%
441
84%
469
497
95.0%
531
79%
40%
38%
43%
36%
55%
313
0%
300
100
Tower approach (F)
Tower range + approach (F)
110
20
101.0
Tower water temp. (F)
81.8
83.3
80.3
79.1
95.2
97.6
91.1
85.9
86.8
87.8
70
4.33 4.08 4.27 4.53
600
400
536
310
307
304
412
337
800
200
0
SYSTEM TOTAL (kW)
15
88.7
85.6
85.8
83.2
10
80.5
6.86 6.83 6.85 6.91
77.3
481
102.5
86.4
80
1000
625
872
6.84
5.57
5.32
5.19
Tower approach (F)
97.7
99.2
91.4
83.8
487
905
Figure 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.
FIGURE 1-5: Chiller performance
85.8
506
536
FIGURE 1-7: Systems total kW
demand
Total EVAPORATOR Ton
(lwt)tower (F)
200
1200
765
0
(ASHRAE Design) Chiller Performance Peak summer
90
1000
600
0
100
1,379 1,426 1,122
1,316 1,339
TIME of DAY
154
120
(ewt)tower (F)
1400
1,129
1200
200
221
20%
117 106 101
1600
1400
400
30%
10%
1800
1600
800
400
66%
369
42%
500
kW
80%
50%
System (kW)
1
2000
1,770
System (kW)
(Chiller)% power
5
60
50
0
Wet bulb (F)
(ASHRAE Design) TOWER PERFORMANCE-Peak summer Wk day
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.
Kirby Nelson PE
Page 7
(AHU)Fan kW
(plant)kW
(Bld)kW
(System)kW
Duct heat kW
FA Heat kW
(Bld)kW
(AHU)Fan kW
(plant)kW
(System)kW
2000
1,653 1,707
1,770
1500
481
731
536
1500
2000
1,379
1,316 1,339
0.00
1000
765
625
1500
1,426
905
1000
1000
731
629
532
348
0
1500
(kW)
731
487
2000
1,122
1000
500
2000
(kW)
kW
1,129
506
FA Heat kW
Dry bulb (F)
DRY BULB (F)
1,611
Duct heat kW
731
872
500
0.00
536
500
410
310
307
304
412
337
0
0
450
135
525
500
169
0
0
0
TIME OF DAY
SYSTEM kW-All electric-498,600 sqft Bld-24 hr. ASHRAE Design
Figure 1-8: ASHRAE design kW
demand components
Figures 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.
TIME OF DAY
SYSTEM kW -All electric 498,600 sqft Bld. (min kW) Design
Figure 1-9: (Min kW design) kW
components at design day
BLD sq-ft =
ALL ELECTRIC
Design
BLD.24hr-kW=
(Fan)24hr-kW =
(Duct)24hr-heat kW=
(FA)24hr-heat kW=
Heat24hr-total kW=
Plant24hr-kW=
SYST 24hr-kW =
498,600
Peak day
24hr
10,096
6,230
0
0
0
8,453
24,779
BLD sq-ft =
ALL ELECTRIC
Wk. Day
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 =
14,683
10,096
24,779
(CCWS)24hr-kW=
BLD.24hr-kW=
Total24hr-kW =
Table 1-1: ASHRAE design 24 hour at
design day weather
Tables 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.
Kirby Nelson PE
498,600
Peak design
24hr
10,096
1,763
0
0
0
7,027
18,887
8,791
10,096
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.
Page 8
Average summer performance
(Temp)wet bulb
(Temp)dry bulb
% Clear Sky
100
100
95
95
85
Air Temperature (F)
80
75
76.0
74.0
72.0
70.0
70
65
69
68
60
67
79.0
83.0
81.0
90
81.0
78.0
85
76.0
67.0
66
65
80
75
71.0
65
68
73
70
72
71
70
70
65
60
55
55
50
50
45
45
40
40
35
35
30
AIR TEMPerature (F)
90
30
TIME OF DAY
Average summer weather day
Figure 1-10: Assumed average
summer weather day
Figure 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%.
(min kW) Design (kW)
ASHRAE Design (kW)
DRY BULB TEMPERATURE (F)
2000
2000
1800
1,360
System (kW)
1400
1,448
1,511
912
1,059 1,102
1600
1400
1200
1000
1800
1,598
1,181
1,236
1200
954
600
800
585
477
465
459
486
703
696
400
200
1000
697
800
477
295
298
319
314
0
System (kW)
1600
600
400
379
200
0
TIME of DAY
SYSTEM TOTAL (kW)
Figure 1-11: Systems total kW demand
Figure 1-11 illustrates the same pattern as Figure
1-7 but reduced values as expected. The following
charts and tables compare the two designs.
Kirby Nelson PE
Page 9
(AHU)Fan kW
(plant)kW
(Bld)kW
(System)kW
Duct heat kW
FA Heat kW
(Bld)kW
(AHU)Fan kW
(plant)kW
DRY BULB (F)
2000
477
465
459
1,181
1,598
1,059
1500
954
731
731
1000
697
486
1000
703
731
0
TIME OF DAY
SYSTEM kW-All electric-498,600 sqft Bld-24 hr. ASHRAE Design
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.
498,600
Avg Summer
24hr
10,096
9,080
0
0
(CCWS)24hr-kW=
BLD.24hr-kW=
Total24hr-kW =
0
5,723
24,900
14,803
10,096
24,900
Table 1-3: (ASHRAE design) 24 hours average
summer weather
Tables 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.
ALL ELECTRIC SYSTEM
Design
W/sqft
ASHRAE
BLD.24hr-W/sq ft- =
20.25
(Fan)24hr-W/sq ft- =
18.21
Plant24hr-W/sq ft-=
11.48
(Heat)24hr-W/sq ft-=
Syst Total24hr-W/sq ft-=
0.00
49.94
90 day (bEQ)=
FUEL HEAT SYSTEM
Bld,Fan,Plant24hr-W/sq ft-=
Heat24hr-btu/sq ft=
Syst Total24hr-=
90 day (bEQ)=
49.94
0.00
477
295
298
319
369
314
Kirby Nelson PE
500
136
0
0
TIME OF DAY
SYSTEM kW -All electric 498,600 sqft Bld. (min kW) Design
Figure 1-13: (min kW design) kW components
BLD sq-ft = 498,600
ALL 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= 0
Heat24hr-total kW=
44
Plant24hr-kW=
4,567
SYST 24hr-kW =
16,119
(CCWS)24hr-kW=
BLD.24hr-kW=
Total24hr-kW =
6,022
10,096
16,119
Table 1-5: (min kW design) 24 hours average
summer weather
kbtu/sqft-day
(Min kW)
ALL ELECTRIC SYSTEM
Table 1-4: (ASHRAE design)(bEQ) estimate
The min kW Design and control concepts provide
significantly better (bEQ) performance at average
summer conditions and better performance as
weather conditions cool.
379
218
(bEQ)day
0.069
0.062
0.039
0.000
0.170
15.34
(bEQ)day
0.170
0.000
0.170
15.34
731
696
500
585
500
0
1,236
1,102
1000
109
BLD sq-ft =
ALL ELECTRIC
Design
BLD.24hr-kW=
(Fan)24hr-kW =
(Duct)24hr-heat kW=
(FA)24hr-heat kW=
Heat24hr-total kW=
Plant24hr-kW=
SYST 24hr-kW =
FA Heat kW
1500
(kW)
1,511
912
1000
500
1,448
(kW)
kW
1,360
Duct heat kW
1500
2000
1500
(System)kW
Dry bulb (F)
BLD.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
Bld,Fan,Plt24hr-W/sq ft-=
Heat24hr-btu/sq ft=
Syst Total24hr-=
90 day (bEQ)=
Wk. Day
W/sqft
kbtu/sqft-day
(bEQ)day
20.25
0.069
2.83
0.010
9.16
0.031
0.09
0.000
32.33
0.110
9.93
(bEQ)day
32.24
0.110
0.38
0.0004
0.110
9.94
Table 1-6: (min kW Design)(bEQ) estimate
Page 10
Average Spring/Fall Weather
(Temp)wet bulb
(Temp)dry bulb
100
100
95
95
90
90
85
85
80
80
75
75
70
70
65
60
55
55.0
52.0
50.0
50
45
49.0
48.0
44.0
50
48
40
53
56
60.0
58
58.0
65
56.0
56
54
54.0
52
47
46
42
35
45.0
58.0
60
55
AIR TEMPerature (F)
Air Temperature (F)
% Clear Sky
50
45
40
43
35
30
30
TIME OF DAY
Spring/Fall weather day
Figure 1-14: Average spring/fall weather day
Figure 1-14 illustrates the assumed average
spring/fall weather and Figure 1-15 gives the
difference in kW performance of the two designs.
(min kW) Design (kW)
ASHRAE Design (kW)
DRY BULB TEMPERATURE (F)
1,344
1400
1,051
1,220
1,132 1,110
System (kW)
1000
1000
961
800
933
964
968
800
727
600
400
1200
600
648
436
463
485
463
454
200
456
System (kW)
1200
1400
1,309 1,314
1,235
1,142 1,146 1,107
1,095
400
200
0
0
TIME of DAY
SYSTEM TOTAL (kW)
Figure 1-15: Systems total kW
demand
Kirby Nelson PE
Page 11
(AHU)Fan kW
(plant)kW
(Bld)kW
(System)kW
Duct heat kW
FA Heat kW
(Bld)kW
(AHU)Fan kW
(plant)kW
(System)kW
1,235
1,142 1,146 1,107
1,220
kW
659.9
1500
1000
1000
1500
1,132 1,110
1000
731
1500
731
500
961
727
(kW)
1,051 1,095
1,309 1,314
(kW)
1,344
500
133
436
463
394
188
0
933
731
964
1000
968
731
648
500
371
FA Heat kW
Dry bulb (F)
DRY BULB (F)
1500
Duct heat kW
485
463
454
456
500
229.4
0
79
104
0
89
148
0
TIME OF DAY
SYSTEM kW-All electric-498,600 sqft Bld-24 hr. ASHRAE Design
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 =
ALL ELECTRIC
Design
BLD.24hr-kW=
(Fan)24hr-kW =
(Duct)24hr-heat kW=
(FA)24hr-heat kW=
Heat24hr-total kW=
Plant24hr-kW=
SYST 24hr-kW =
498,600
Spring/Fall
24hr
10,096
6,587
8,654
0
8,654
3,074
28,411
(CCWS)24hr-kW=
BLD.24hr-kW=
Total24hr-kW =
18,315
10,096
28,411
Table 1-7: (ASHRAE design) 24 hours average
spring/fall weather
Tables 1-7 & 1-8 illustrate the difference in 24 hour
consumption and Tables 1-9 & 1-10 illustrate (bEQ)
based on 24 hour consumption.
Design
ALL ELECTRIC SYSTEM W/sqft
ASHRAE
BLD.24hr-W/sq ft- =
20.25
(Fan)24hr-W/sq ft- =
13.21
Plant24hr-W/sq ft-=
6.17
(Heat)24hr-W/sq ft-=
Syst Total24hr-W/sq ft-=
17.36
56.98
185 day (bEQ)=
FUEL HEAT SYSTEM
Bld,Fan,Plant24hr-W/sq ft-=
39.63
Heat24hr-btu/sq ft=
Syst Total24hr-=
185 day (bEQ)=
74.04
kbtu/sqft-day
(bEQ)day
0.069
0.045
0.021
0.059
0.194
35.98
(bEQ)day
0.135
0.074
0.209
38.72
Table 1-9: (bEQ) estimate
Kirby Nelson PE
TIME OF DAY
SYSTEM kW -All electric 498,600 sqft Bld. (min kW) Design
Figure 1-17: (min kW design) kW
components
BLD sq-ft =
ALL ELECTRIC
Wk. Day
BLD.24hr-kW=
(Fan)24hr-kW =
(Duct)24hr-heat kW=
(FA)24hr-heat kW=
Heat24hr-total kW=
Plant24hr-kW=
SYST 24hr-kW =
498,600
Spring/Fall
24hr
10,096
1,034
2,494
0
2,494
2,290
15,914
(CCWS)24hr-kW=
BLD.24hr-kW=
Total24hr-kW =
5,818
10,096
15,914
Table 1-8: (min kW design) 24 hours average
spring/fall weather
(Min kW)
ALL ELECTRIC SYSTEM
BLD.24hr-W/sq ft- =
(Fan)24hr-W/sq ft- =
Plant24hr-W/sq ft-=
(Heat)24hr-W/sq ft-=
Syst Total24hr-W/sq ft-=
185 day (bEQ)=
FUEL HEAT SYSTEM
Bld,Fan,Plt24hr-W/sq ft-=
Heat24hr-btu/sq ft=
Syst Total24hr-=
185 day (bEQ)=
Wk. Day
W/sqft
kbtu/sqft-day
(bEQ)day
20.25
0.069
2.07
0.007
4.59
0.016
5.00
0.017
31.92
0.109
20.15
(bEQ)day
26.92
0.092
21.34
0.021
0.113
20.94
Table 1-10: (bEQ) estimate
Page 12
Average winter weather
(Temp)wet bulb
(Temp)dry bulb
% Clear Sky
50
50
45
45
40
35
30
25
35.0
34.0
32.0
29.0
27.0
29
27
28.0
26.0
25.0
24.0
26
35
32.0
30.0
34
32
30
32
30
28
25
25
24
20
35
34
34.0
AIR TEMPerature (F)
Air Temperature (F)
40
20
15
15
10
10
TIME OF DAY
Avg Winter weather day
Figure 1-18: Assumed average winter weather day
Figure 1-18 illustrates the assumed average winter
weather and Figure 1-19 gives the difference in kW
performance of the two designs.
(min kW) Design (kW)
ASHRAE Design (kW)
DRY BULB TEMPERATURE (F)
2,973
2500
2,792
2,697
3000
2,802
2,484
2500
1500
1,870
1,791 1,841
2,100
1,962
1,903 1,886
1,507
1,351
1000
1,403 1,343 1,399
2000
1500
1,113
869
894
909
969
963
500
940
System (kW)
System (kW)
2000
1000
500
0
0
TIME of DAY
SYSTEM TOTAL (kW)
Figure 1-19: Systems total kW
demand
Kirby Nelson PE
Page 13
(AHU)Fan kW
(plant)kW
(Bld)kW
(System)kW
Duct heat kW
FA Heat kW
(Bld)kW
(AHU)Fan kW
(plant)kW
(System)kW
3000
2,792
1,507
1500
1500
731
731
500
869
894
909
1500
1,343
1,399
1,113
969
963
731
1000
500
0
1000
1,403
1,351
2000
(kW)
1,903 1,886
1500
1000
2000
2500
2,100
1,962
(kW)
kW
1,791 1,841 1,870
2000
3000
2,802
2,484
2500
2000
2,697
FA Heat kW
Dry bulb (F)
DRY BULB (F)
2,973
Duct heat kW
940
1000
731
500
500
0
0
0
TIME OF DAY
SYSTEM kW-All electric-498,600 sqft Bld-24 hr. ASHRAE Design
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 =
ALL ELECTRIC
Design
BLD.24hr-kW=
(Fan)24hr-kW =
(Duct)24hr-heat kW=
(FA)24hr-heat kW=
Heat24hr-total kW=
Plant24hr-kW=
SYST 24hr-kW =
498,600
Winter
24hr
10,096
8,979
29,183
1,695
30,878
4,247
54,200
(CCWS)24hr-kW=
BLD.24hr-kW=
Total24hr-kW =
44,104
10,096
54,200
Table 1-11: (ASHRAE design) 24 hours average
winter weather
Tables 1-11 & 1-13 illustrate the difference in 24
hour consumption and Tables 1-12 & 1-14
illustrate (bEQ) based on 24 hour consumption.
ALL ELECTRIC SYSTEM
Design
W/sqft
ASHRAE
BLD.24hr-W/sq ft- =
20.25
(Fan)24hr-W/sq ft- =
18.01
Plant24hr-W/sq ft-=
8.52
(Heat)24hr-W/sq ft-=
Syst Total24hr-W/sq ft-=
61.93
108.70
90 day (bEQ)=
FUEL HEAT SYSTEM
Bld,Fan,Plant24hr-W/sq ft-=
46.78
Heat24hr-btu/sq ft=
Syst Total24hr-=
90 day (bEQ)=
264.20
Figure 1-21: (min kW design) kW components
BLD sq-ft =
ALL ELECTRIC
Wk. Day
BLD.24hr-kW=
(Fan)24hr-kW =
(Duct)24hr-heat kW=
(FA)24hr-heat kW=
Heat24hr-total kW=
Plant24hr-kW=
SYST 24hr-kW =
498,600
Winter
24hr
10,096
1,274
12,962
1,695
14,657
1,292
27,320
(CCWS)24hr-kW=
BLD.24hr-kW=
Total24hr-kW =
17,224
10,096
27,320
Table 1-13: (min kW design) 24 hours average
winter weather
kbtu/sqft-day
(Min kW)
(bEQ)day
0.069
0.061
0.029
0.211
0.371
33.39
(bEQ)day
0.160
0.264
0.424
ALL ELECTRIC SYSTEM
Wk. Day
W/sqft
BLD.24hr-W/sq ft- =
20.25
(Fan)24hr-W/sq ft- =
2.55
38.15
Table 1-12: (bEQ) estimate
Kirby Nelson PE
TIME OF DAY
SYSTEM kW -All electric 498,600 sqft Bld. (min kW) Design
Plant24hr-W/sq ft-=
2.59
(Heat)24hr-W/sq ft-=
Syst Total24hr-W/sq ft-=
29.40
54.79
90 day (bEQ)=
FUEL HEAT SYSTEM
Bld,Fan,Plt24hr-W/sq ft-=
25.40
Heat24hr-btu/sq ft=
Syst Total24hr-=
90 day (bEQ)=
125.42
kbtu/sqft-day
(bEQ)day
0.069
0.009
0.009
0.100
0.187
16.83
(bEQ)day
0.087
0.125
0.212
19.09
Table 1-14: (bEQ) estimate
Page 14
CONCLUSIONS of CHAPTER 1
The 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
Summer-3m
spring/fall-6m
Winter-3m
Est. annual
(bEQ)
ASHRAE design
(bEQ)
15.34
35.98
33.39
84.71
Min kW design
(bEQ)
9.93
20.15
16.83
46.91
TABLE 1-15: Chicago (bEQ) Estimates
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
Summer -5m
spring/fall-4m
Winter -3m
Est. annual
(bEQ)
ASHRAE design
(bEQ)
24.37
25.62
16.96
66.95
Min kW design
(bEQ)
18.29
16.02
9.36
43.67
Table 1-16: Houston (bEQ) Estimate
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
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 or
http://www.energycodes.gov/achieving-30-goalenergy-and-cost-savings-analysis-ashraestandard-901-2010
BLD ft2 =
%clear sky =
# floors =
Tdry-bulb =
Infil-CFM =
Roof ft =
Twet-bulb=
Infilsen-ton =
N/S wall ft2 =
WallNtrans ton=
2
2
E/W wall ft =
InfilLat-ton =
Wall % glass=
WallStrans ton=
WallEtrans ton=
Glass U =
Wall U =
WallWtranston=
GlassN trans ton =
Glass SHGC =
Wall emitt =
GlassS trans ton =
GlassE-trans ton =
RoofTrans ton =
Roofsky lite ton =
GlassW-trans ton =
GlassN-solar-ton =
Peopleton =
plugton =
kW GlassS-solar-ton =
Lightton=
GlassW-solar ton =
GlassTot-solar-ton =
(int-cfm)to-per-ret=
Total Bldint-ton =
BLD kW=
AHU kW=
(int cfm)per-ton =
Tot Bldper-sen-ton =
WallTot trans ton =
GlassTot-trans-ton=
GlassE-solar ton =
Tstat-int=
(Bld)int.air-ton=
Tstat-per =
SITE kW =
^
Design
4PM
BUILDING NOMENCLATURE:
Building structure;
BLD ft2 = air conditioned space
Kirby Nelson PE
<
^ (Bld)per.air-ton=
>
v
return
air
# Floors = number of building floors
Roof ft2 = roof square feet
N/S wall ft2 =north/south wall square feet
E/W wall ft2 =east/west wall square feet
Wall % glass = percent of each wall that is glass
Glass U = glass heat transfer coefficient
Wall U = wall heat transfer coefficient
Glass SHGC = glass solar heat gain coefficient
Wall emit = wall solar index
Building 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 kW
PlugtkW = kW demand due to plug loads
Lightton = 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 building
Total Bldint-ton = total building interior load (ton)
Tstat-int = interior stat set temperature (F)
Bldint-air-ton = supply air ton to offset interior load
Building perimeter space;
%clear sky = percent solar that hits building
Tdry 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 CFM
Infilsen-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)
Page 16
Tstat-per = perimeter stat set temperature (F)
Bldper-air-ton = supply air ton to offset perimeter load
Tair supply int=
ASHRAE
^
Tair supply per=
Design
ABS Bld Ton =
Ton
^
kW
Ton
(fan)int-ter=
kW
V
(fan)per-ter=
Theat-air=
(D)heat =
Treheat air =
(D)reheat =
(D)int-air-ton=
Tair coils =
(D)int-CFM=
>>>(Coil)sen-ton=
(coil)cap-ton=
Interior
duct
^
^
(coil)H2O-ft/sec=
(D)per-air-ton=
Tair coils=
(D)per-CFM=
(coil)gpm=
UAdesign=
COIL
(coil)des-ft/sec=
Peri
duct
^
^
UA=
(one coil)ton=
(H)coil=
LMTD=
(COIL)L+s-ton=
^
<<<<
V
^ (H)coil-des=
^
Tair VAV=
(FAN)VAV-CFM=
(Air)ret-CFM =
TBLD-AR =
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 =
TEx =
temp pink
Exsen-ton =
gpm orange
V
FIGURE 2A
Air handler system
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 fans
Theat-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 air
Treheat 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 duct
COIL 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 coil
UAdesign = coil UA design value
UA = 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=
^
Tair supply int=
Design
ASHRAE
^
Ton
4PM
Design
^ (Bld)per.air-ton=
^
kW
(fan)int-ter=
air
Tair supply per=
ABS Bld Ton =
Ton
kW
UA=
(one coil)ton=
(H)coil=
LMTD=
(COIL)L+s-ton=
(Bld)int.air-ton=
COIL
(coil)des-ft/sec=
AIR HANDLER DUCT SYSTEM NOMENCLATURE
V
(fan)per-ter=
Theat-air=
(D)heat =
^
^
^
<<<<
V
^ (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)
Treheat air =
(COIL)L+s-ton=
(D)reheat =
<<<<
(D)int-air-ton=
Interior
Tair coils =
duct
(D)int-CFM=
^
^ (H)coil-des=
^
(D)per-air-ton=
Peri
Tair VAV=
(FAN)VAV-CFM=
Tair coils=
duct
(FAN)ton-VAV=
(FAN)ret-kW=
Fan
(D)per-CFM=
^
(FAN)kW-VAV=
(FAN)ret-ton=
V
Duct system nomenclature
Tair 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 duct
Tair coils = supply air temperature off coils to duct
(D)int-CFM = supply air CFM to interior duct
(ABS Bld Ton) = absolute building load on (CCWS)
Kirby Nelson PE
^
TBLD-AR =
^
26 F.A.Inlet
statFA=
(Air)ret-CFM =
Return
(Air)ret-ton =
Tar-to-VAV =
^
VAVret-ton =
26 VAV FANS
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
gpm orange
TEx =
Exsen-ton =
V
VAV FAN SYSTEM NOMENCLATURE
Page 17
Fresh 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 temperature
Air 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 fans
TAR to VAV = TBLD-AR + delta T due to return fans kW
VAVret-ton = return (ton) to VAV fans inlet
InfilVAV-Lat-ton = infiltration latent (ton) to VAV fans
VAVret-CFM = return CFM to VAV fans inlet
InfilCFM-ton = load (ton) due to infiltration CFM
Exhaust air nomenclature
ExLat-ton = latent load (ton) exhausted
ExCFM = CFM of exhaust air
TEx = temperature of exhaust air
Exsen-ton = sensible load (ton) exhausted
VAV Fans nomenclature
Tair-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 demand
Tret+FA = return and fresh air mix temperature (F)
(dh) = VAV air static pressure (ft)
Efan-VSD = VAV fans efficiency
AIR SIDE SYSTEM PLUS BUILDING
BLD ft2 =
%clear sky =
# floors =
Tdry-bulb =
Infil-CFM =
Roof ft =
Twet-bulb=
Infilsen-ton =
2
N/S wall ft2 =
WallNtrans ton=
E/W wall ft2 =
WallStrans ton=
Wall % glass=
WallEtrans ton=
Glass U =
Wall U =
WallWtranston=
GlassN trans ton =
Glass SHGC =
Wall emitt =
GlassS trans ton =
GlassE-trans ton =
RoofTrans ton =
GlassW-trans ton =
Roofsky lite ton =
GlassN-solar-ton =
Peopleton =
kW GlassS-solar-ton =
plugton =
Lightton=
GlassW-solar ton =
(int-cfm)to-per-ret=
BLD kW=
InfilLat-ton =
<
WallTot trans ton =
GlassTot-trans-ton=
GlassE-solar ton =
Total Bldint-ton =
GlassTot-solar-ton =
(int cfm)per-ton =
AHU kW=
Tstat-int=
^
Design
Tair supply int=
^
air
Tair supply per=
Design
ABS Bld Ton =
^
kW
Ton
(fan)int-ter=
return
^ (Bld)per.air-ton=
4PM
ASHRAE
Ton
v
Tstat-per =
SITE kW =
(Bld)int.air-ton=
>
Tot Bldper-sen-ton =
kW
V
(fan)per-ter=
Theat-air=
(D)heat =
Treheat air =
(D)reheat =
(D)int-air-ton=
Tair coils =
Interior
duct
(D)int-CFM=
>>>(Coil)sen-ton=
(D)per-air-ton=
Tair coils=
^
^
(D)per-CFM=
(coil)gpm=
(coil)cap-ton=
COIL
(coil)des-ft/sec=
UA=
(one coil)ton=
(H)coil=
LMTD=
<<<<
^
V
^ (H)coil-des=
^
Tair VAV=
(FAN)VAV-CFM=
(Air)ret-CFM =
TBLD-AR =
Return
(FAN)ton-VAV=
(FAN)ret-kW=
Fan
(FAN)kW-VAV=
(FAN)ret-ton=
V
^
26 F.A.Inlet
statFA=
^
^
UAdesign=
(coil)H2O-ft/sec=
(COIL)L+s-ton=
Peri
duct
^
26 VAV FANS
(Air)ret-ton =
Tar-to-VAV =
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
gpm orange
Kirby Nelson PE
TEx =
Exsen-ton =
V
Page 18
Condenser
(H)T-pipe=
Tower
TCR=
> gpmT=
> (ewt)T=
tfan-kW=
TCR-app=
(COND)ton=
(H)T-total=
PT-heat =
(H)T-static =
Trange=
Tfan-kW=
tfan-% =
(H)cond=
< pT-kW=
EfTpump=
(lwt)T =
tton-ex=
(cond)ton=
Pipesize-in =
(cond)ft/sec=
<
Tapproach =
T #=
Ptower # =
T-Ton-ex=
Trg+app =
Compressor
ASHRAE Design
(chiller)kW=
Chicago
(chiller)lift=
Large
Office
(chiller)% =
Peak day
Design
(chiller)#=
Weather
%clear sky =
(CHILLER)kW=
(chiller)kW/ton=
90.1-2010
4PM
conditions Tdry bulb =
Twet bulb =
Plant kW =
>
Evaporator
(evap)ton=
TER=
TER-app=
^
EVAPton=
(H)evap=
(evap)ft/sec=
(evap)des-ft/sec=
^
V
gpmevap=
Psec-heat-ton =
(lwt)evap =
>
(H)pri-total=
^
v
(H)pri-pipe=
Tbp=
(H)pri-fitings=
gpmbp=
(H)sec=
(Ef)c-pump=
(H)pri-bp=
(H)sec-pipe=
Pc-heat-ton=
^
Psec-kW=
< pc-kW=
Efsec-pump =
v
(ewt)evap =
> (ewt)coil=
Efdes-sec-p =
PLANTton =
(H)sec-bp=
Pipesize-in =
< (gpm)sec=
< (lwt)coil=
Pchiller-# =
CENTRAL PLANT
Nomenclature will be defined by addressing each
component of the plant.
Primary/secondary pumping nomenclature
gpmevap = 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 pump
Pc-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)
Kirby Nelson PE
Psec-heat-ton = secondary pump energy not into
system (ton), goes to atmosphere
Psec-kW = kW demand of secondary pumps
Efdes-sec-p = design efficiency of secondary pumping
Efsec-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 plant
Pipesize-in = secondary pipe size (inches)
(lwt)coil = temperature of water leaving coil (F)
Condenser nomenclature:
(cond)ton = load (ton) on one condenser
TCR = 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 ton
Evaporator
(evap)ton = load (ton) on one evaporator
TER = 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 velocity
Tower piping nomenclature
Pipesize-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 demand
EfT-pump = tower pump efficiency
Ptower # = number of tower pumps
(H)T-pipe = total tower pump head (ft)
Page 19
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 fan
Tfan-kW = tower fan kW of fans on
tfan-% = percent tower fan speed
tton-ex = ton exhaust by one tower
T# = number of towers on
Tton-ex = ton exhaust by all towers on
Trg+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
Performance
4PM
4PM
All ElectricFuel Heat
Design
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 =
kW
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
Design
BLD sq ft =
Fuel heat
Peak day
Design
24hr
BLD.24hr-kW=
(Fan)24hr-kW =
(Duct)24hr-heat therm =
(FA)24hr-heat therm =
Heat24hr-total therm =
Plant24hr-kW=
SYST 24hr-kW =
Therm
24 Hour performance, heat with fuel
THERM
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
Pumptot-heat-ton =
AHU ExLat-ton =
BLD.kW=
AHU Exsen-ton =
CCWSkW =
Tower Tton-Ex =
SystkW =
Total Eout-ton =
Performance table at given hour
ASHRAE
ALL ELECTRIC SYSTEM
Design
W/sqft
kbtu/sqft-day
(bEQ)day
BLD.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)=
(bEQ)day
FUEL HEAT SYSTEM
Bld,Fan,Plant24hr-W/sq ft-=
Heat24hr-btu/sq ft=
Syst Total24hr-=
90 day (bEQ)=
49.70
0.00
(bEQ) estimate
Next the full system energy equilibrium (SEE)
schematic.
Kirby Nelson PE
Page 20
2
Condenser
(cond)ton=
Pipesize-in =
%clear sky =
# floors =
Tdry-bulb =
Infil-CFM =
Twet-bulb=
Infilsen-ton =
2
Tower
(H)T-pipe=
BLD ft =
Roof ft =
2
TCR=
> gpmT=
> (ewt)T=
tfan-kW=
N/S wall ft =
TCR-app=
(COND)ton=
(H)T-total=
PT-heat =
(H)T-static =
Trange=
Tfan-kW=
tfan-% =
E/W wall ft =
Wall % glass=
WallStrans ton=
WallEtrans ton=
(H)cond=
(cond)ft/sec=
< pT-kW=
EfTpump=
(lwt)T =
Tapproach =
tton-ex=
T #=
Glass U =
Wall U =
WallWtranston=
GlassN trans ton =
Glass SHGC =
Wall emitt =
GlassS trans ton =
GlassE-trans ton =
RoofTrans ton =
Roofsky lite ton =
GlassW-trans ton =
GlassN-solar-ton =
Peopleton =
plugton =
kW GlassS-solar-ton =
<
Ptower # =
Compressor
(chiller)kW=
ASHRAE Design
Chicago 90.1-2010
(chiller)lift=
(chiller)% =
Large
Peak day
Office
Design
(chiller)#=
Weather
%clear sky =
Lightton=
GlassW-solar ton =
(CHILLER)kW=
conditions Tdry bulb =
(int-cfm)to-per-ret=
BLD kW=
(chiller)kW/ton=
Twet bulb =
Total Bldint-ton =
4PM
^
(int cfm)per-ton =
^
Design
ABS Bld Ton =
^
kW
Ton
(D)heat =
EVAPton=
Treheat air =
(H)evap=
(D)reheat =
(D)int-air-ton=
Interior
Tair coils =
(D)int-CFM=
duct
^
Tair coils=
(D)per-CFM=
duct
^
^
(coil)gpm=
UAdesign=
^
V
gpmevap=
Psec-heat-ton =
(lwt)evap =
(H)pri-total=
v
> Psec-kW=
Efdes-sec-p =
(H)pri-pipe=
Tbp=
Efsec-pump =
(H)pri-fitings=
gpmbp=
(H)sec=
(Ef)c-pump=
(H)pri-bp=
v
< pc-kW=
> (ewt)coil=
>>>(Coil)sen-ton=
(coil)cap-ton=
(coil)H2O-ft/sec=
PLANTton =
(coil)des-ft/sec=
(H)sec-bp=
Pipesize-in =
(COIL)L+s-ton=
< (gpm)sec=
< (lwt)coil=
(H)sec-pipe=
Pc-heat-ton=
^
(ewt)evap =
Chicago
4PM
4PM
<<<<
All ElectricFuel Heat
Design
chillerkW/evapton=
BLD.kW=
(plant)kW/site ton=
(Fan)kW =
CCWSkW/bld ton=
Ductheat=
kW
THERM
COIL
V
UA=
(H)coil=
^
(FA)heat=
(Site)kW-Ein-ton =
Heat total =
Tdry bulb =
PlantkW-Ein-ton =
PlantkW=
Fresh air >
Total Ein-ton =
SystkW =
Twet bulb =
AHU ExLat-ton =
BLD.kW=
SEE SCHEMATIC
AHU Exsen-ton =
CCWSkW =
Tower Tton-Ex =
SystkW =
>>>
Tair VAV=
(FAN)VAV-CFM=
(Air)ret-CFM =
TBLD-AR =
Return
(FAN)ton-VAV=
(FAN)ret-kW=
Fan
(FAN)kW-VAV=
(FAN)ret-ton=
V
^
26 VAV FANS
(Air)ret-ton =
Tar-to-VAV =
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=
Pumptot-heat-ton =
(FA)kW=
ton blue
V
^ (H)coil-des=
^
26 F.A.Inlet
statFA=
Peri
(one coil)ton=
^
WeatherEin-ton =
Total Eout-ton =
(D)per-air-ton=
LMTD=
Pchiller-# =
Performance
kW
(fan)per-ter=
Theat-air=
(evap)ft/sec=
(evap)des-ft/sec=
^
air
Tair supply per=
Design
(fan)int-ter=
return
^ (Bld)per.air-ton=
4PM
TER-app=
^
v
Tstat-per =
TER=
^
>
Tot Bldper-sen-ton =
ASHRAE
Ton
(evap)ton=
GlassTot-solar-ton =
SITE kW =
Tair supply int=
Evaporator
GlassTot-trans-ton=
AHU kW=
(Bld)int.air-ton=
>
WallTot trans ton =
GlassE-solar ton =
Tstat-int=
Plant kW =
<
WallNtrans ton=
2
T-Ton-ex=
Trg+app =
InfilLat-ton =
ExLat-ton =
ExCFM =
water temp pink
air cfm purplewater gpm orange
air temp green
TEx =
Exsen-ton =
V
kW red
System Energy Equilibrium (SEE) Schematic
Kirby Nelson PE
Page 21