Chicago CCWS Design-cont Manual ASHRAE vs min kW Web viewSystem energy equilibrium (SEE) models and schematics can be developed for any condition of weather and operational conditions

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.


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/


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


http://www.energycodes.gov/achieving-30-goal-energy-and-cost-savings-analysis-ashrae-standard-901-2010



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.


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.


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:


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


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






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


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

400

600

800

1000

1200

1400

1600

1800

2000

0

200

400

600

800

1000

1200

1400

1600

1800

2000


Syst

em (k

W)

Syst

em (k

W)

TIME of DAY

SYSTEM TOTAL (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.


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



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







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.


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



Figure 1-13: (min kW design) kW components

BLD sq-ft = 498,600ALL ELECTRIC Avg Summer







Table 1-5: (min kW design) 24 hours average summer weather

(Min kW) Wk. Day kbtu/sqft-day




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


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

1200

1400


Syst

em (k

W)

Syst

em (k

W)

TIME of DAY

SYSTEM TOTAL (kW)


Figure 1-15: Systems total kW demand


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



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


(Fan)24hr-kW = 6,587(Duct)24hr-heat kW= 8,654

(FA)24hr-heat kW= 0Heat24hr-total kW= 8,654




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.






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


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




BLD sq-ft = 498,600ALL ELECTRIC Spring/Fall



(FA)24hr-heat kW= 0Heat24hr-total kW= 2,494




Table 1-8: (min kW design) 24 hours average spring/fall weather






Heat24hr-btu/sq ft= 21.34 0.021Syst Total24hr-= 0.113

185 day (bEQ)= 20.94


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


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


Syst

em (k

W)

Syst

em (k

W)

TIME of DAY

SYSTEM TOTAL (kW)


Figure 1-19: Systems total kW demand


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



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



(FA)24hr-heat kW= 1,695Heat24hr-total kW= 30,878




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.






Bld,Fan,Plant24hr-W/sq ft-= 46.78 0.160Heat24hr-btu/sq ft= 264.20 0.264Syst Total24hr-= 0.42490 day (bEQ)= 38.15



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




BLD sq-ft = 498,600ALL ELECTRIC Winter



(FA)24hr-heat kW= 1,695Heat24hr-total kW= 14,657




Table 1-13: (min kW design) 24 hours average winter weather






Heat24hr-btu/sq ft= 125.42 0.125Syst Total24hr-= 0.21290 day (bEQ)= 19.09


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.


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;





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=





(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


(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.




<<<< 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






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


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=








<<<< 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







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)



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



=(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.


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


Documents

Chicago CCWS Design-cont Manual ASHRAE vs min kW Web viewSystem energy equilibrium (SEE) models and schematics can be developed for any condition of weather and operational conditions