Home > Documents > Chapter IV Ducting

# Chapter IV Ducting

Date post: 10-Apr-2018
Category:
View: 219 times
Embed Size (px)

of 26

Transcript
• 8/8/2019 Chapter IV Ducting

1/24

CHAPTER IV

DUCT SIZING

The function of a duct sizing is to transmit air from the air handling apparatus to the

space to be conditioned. To fulfill this function in physical manner, the system must be

designed with prescribe limits available space, frictional loss, sound level, heat and leakage

losses and gains.

Method use: Equal Friction Method

Operating pressure for all terminals = 0.15 in. wg (From HVAC, by McQuiston, 5th Ed, PP 437)

Radius elbows = R/D = 1.25

Initial Duct supply air Velocity = 1 700 fpm (From the Book of Carrier, PP 2-37, Table 7)

Initial Duct return air Velocity = 1 500 fpm (From the Book of Carrier, PP 2-37, Table 7)

• 8/8/2019 Chapter IV Ducting

2/24

• 8/8/2019 Chapter IV Ducting

3/24

ZONE 1

Duct Sizing for Supply Air in Zone 1:

Total number of diffuser = 49

Percent of cfm =

Duct area entering section 1:

Duct area = percent of area times initial duct area (fan at section 1)

All areas are listed in Table 3.1.1

The Duct sizes can then be determined by using Carrier handbook, PP 2-36, Table 6.

Table 3.1.1 listed all the duct size.

The Additional Equivalent Length can be determining from Carrier handbook, PP 2-44,

Table 12.

Duct

Section

Air

Quantity

CFM

Capacity

%

Area

%

Area

ft

Duct

SizeItem

Length

(m)

Length

(ft.)

Equiv.

length

AHU1-A 22399.00 100.00 100 13.18 44 X 46 Duct Elbow 8.6 28.208 25

A-B 19199.16 85.71 89.5 11.79 40 X 46 Duct 4.5 14.76

B-C 15999.32 71.43 78 10.28 40 X 40 Duct 4.5 14.76

C-D 14627.96 65.31 72.5 9.55 38 X 40 Duct 4.5 14.76

D-E 13256.60 59.18 67.5 8.89 34 X 40 Duct 4.5 14.76

E-F 11885.24 53.06 61 8.04 34 X 36 Duct 4.5 14.76

F-36 6399.80 28.57 36.5 4.81 22 X 36 Duct Elbow 5.5 18.04 13

A-1 3199.84 14.29 20.5 2.70 22 X 20 Elbow Duct 1 3.28 11

1-2 2742.72 12.24 18.5 2.44 20 X20 Duct 4.5 14.76

2-3 2285.60 10.20 16.5 2.17 18 X 20 Duct 4.5 14.76

• 8/8/2019 Chapter IV Ducting

4/24

3-4 1828.48 8.16 13 1.71 14 X 20 Duct 4.5 14.76

4-5 1371.36 6.12 10.5 1.38 14 X 16 Duct 4.5 14.76

5-6 914.24 4.08 7 0.92 10 X 16 Duct 4.5 14.76

6-7 457.12 2.04 3.5 0.46 10 X 8 Duct 4.5 14.76

B-8 3199.84 14.29 20.5 2.70 22 X 20 Elbow Duct 1 3.28 11

8-9 2742.72 12.24 18.5 2.44 20 X20 Duct 4.5 14.76

9-10 2285.60 10.20 16.5 2.17 18 X 20 Duct 4.5 14.76

10-11 1828.48 8.16 13 1.71 14 X 20 Duct 4.5 14.76

11-12 1371.36 6.12 10.5 1.38 14 X 16 Duct 4.5 14.76

12-13 914.24 4.08 7 0.92 10 X 16 Duct 4.5 14.76

13-14 457.12 2.04 3.5 0.46 10 X 8 Duct 4.5 14.76

C-15 1371.36 6.12 10.5 1.38 14 X 16 Elbow Duct 1 3.28 9

15-16 914.24 4.08 7 0.92 10 X 16 Duct 4.5 14.76

16-17 457.12 2.04 3.5 0.46 10 X 8 Duct 4.5 14.76

D-18 1371.36 6.12 10.5 1.38 14 X 16 Elbow Duct 1 3.28 9

18-19 914.24 4.08 7 0.92 10 X 16 Duct 4.5 14.76

19-20 457.12 2.04 3.5 0.46 10 X 8 Duct 4.5 14.76

E-21 1371.36 6.12 10.5 1.38 14 X 16 Elbow Duct 1 3.28 9

21-22 914.24 4.08 7 0.92 10 X 16 Duct 4.5 14.76

22-23 457.12 2.04 3.5 0.46 10 X 8 Duct 4.5 14.76

F-24 5484.44 24.49 32.5 4.28 20 X 36 Elbow Duct 1 3.28 22

24-25 5028.32 22.45 29.5 3.89 18 X 36 Duct 4.5 14.76

25-26 4571.20 20.41 27 3.56 16 X 36 Duct 4.5 14.76

26-27 4114.08 18.37 25 3.29 14 X 34 Duct 4.5 14.76

27-28 3656.96 16.33 23 3.03 14 X 34 Duct 4.5 14.7628-29 3199.84 14.29 20.5 2.70 22 X 20 Duct 4.5 14.76

29-30 2742.72 12.24 18.5 2.44 20 X20 Duct 4.5 14.76

30-31 2285.60 10.20 16.5 2.17 18 X 20 Duct 4.5 14.76

31-32 1828.48 8.16 13 1.71 14 X 20 Duct 4.5 14.76

32-33 1371.36 6.12 10.5 1.38 14 X 16 Duct 4.5 14.76

33-34 914.24 4.08 7 0.92 10 X 16 Duct 4.5 14.76

34-35 457.12 2.04 3.5 0.46 10 X 8 Duct 4.5 14.76

36-37 5942.56 26.53 34.5 4.55 20 X 36 Duct 4.5 14.76

37-38 5485.44 24.49 32.5 4.28 20 X 36 Duct 4.5 14.76

38-39 5028.32 22.45 30.5 4.02 18 X 36 Duct 4.5 14.7639-40 4571.20 20.41 27 3.56 16 X 36 Duct 4.5 14.76

40-41 4114.08 18.37 25 3.29 14 X 34 Duct 4.5 14.76

41-42 3656.96 16.33 23 3.03 14 X 34 Duct 4.5 14.76

42-43 3199.84 14.29 20.5 2.70 22 X 20 Duct 4.5 14.76

43-44 2742.72 12.24 18.5 2.44 20 X20 Duct Elbow 4.5 14.76 11

44-45 2285.60 10.20 16.5 2.17 18 X 20 Duct 4.5 14.76

• 8/8/2019 Chapter IV Ducting

5/24

45-46 1828.48 8.16 13 1.71 14 X 20 Duct 4.5 14.76

46-47 1371.36 6.12 10.5 1.38 14 X 16 Duct 4.5 14.76

47-48 914.24 4.08 7 0.92 10 X 16 Duct 4.5 14.76

48-49 457.12 2.04 3.5 0.46 10 X 8 Duct 4.5 14.76

TOTAL LENGTH 759.648 120

The total friction loss in the duct work from fan to last terminal 49 is:

Loss = total equivalent length x friction rate

For the total equivalent length, it appears that the longer run is from AHU 1 to terminal

49: 312.3 + 47 = 359.3 ft.

Friction rate: using Vsupply = 1700 fpm, cfm = 22399, Fr = 0.062 (from chart 7, page 2-33

friction loss for round duct)

Loss = 359.3 ft. x (0.062 in wg /100 ft.)

Loss = 0.223 in wg

The total static pressure required at fan discharge is the sum of the terminal operating

pressure and the loss in the duct work. Credit can be taken for the regain between the

first and last section of the duct.

From chart 7, p. 2-33 of Carrier Handbook with cfm of 457.12 and equivalent circular

duct diameter = 9.8 in., velocity in the last section = 920 fpm.

Using 75% regain coefficient;

Regain = = 0.096 in wg

Therefore, the total static pressure at fan discharge is;

= duct friction + terminal pressure regain

= 0.223 + 0.15 0.096

= 0.277 in wg

Duct Sizing for Return Air in Zone 1:

Total number of diffuser = 14

Percent of cfm =

Duct area entering section 1:

• 8/8/2019 Chapter IV Ducting

6/24

Duct

Section

Air

Quantity

CFM

Capacity

%

Area

%

Area

ft.

Duct

SizeItem

Length

(m)

Length

(ft)

Equiv.

LengthAHU 1 - 1 21049 100.00 100 14.03 46 x 48 Duct Elbow 15.25 50.02 25

1-2 19545.5 92.86 94.5 13.26 46 x 44 Duct 6.46 21.1888

2-3 18042 85.71 89.5 12.56 44 x 44 Duct Elbow 10.6 34.768 24

3-A 7517.5 35.71 44 6.17 30 x 32 Duct Elbow 4.5 14.76 16

A-10 3007 14.29 20.5 2.88 16 x 28 Duct Elbow 4.5 14.76 10

10-11 1503.5 7.14 11.5 1.61 16 x 16 Duct 9 29.52

A-12 4510.5 21.43 28 3.93 22 x 28 Duct 9 29.52

12-13 3007 14.29 20.5 2.88 16 x 28 Duct 9 29.52

13-14 1503.5 7.14 11.5 1.61 16 x 16 Duct 9 29.52

3-4 9021 42.86 51 7.16 32 x 34 Duct 9 29.52

4-5 7517.5 35.71 44 6.17 32 x 30 Duct 9 29.52

5-6 6014 28.57 36.5 5.12 28 X 28 Duct Elbow 9 29.52 15

6-7 4510.5 21.43 28 3.93 22 x 28 Duct 9 29.52

7-8 3007 14.29 20.5 2.88 16 x 28 Duct 9 29.52

8-9 1503.5 7.14 11.5 1.61 16 x 16 Duct 9 29.52

TOTAL LENGTH 430.6968 90

The total friction loss in the duct work from fan to last terminal 14 is:

Loss = total equivalent length x friction rate

For the total equivalent length, it appears that the longer run is from AHU 1 to terminal

9: 86.3 + 64 = 150.3 ft.

Friction rate: using Vsupply = 1500 fpm, cfm = 21049, Fr = 0.047 (from chart 7, page 2-33

friction loss for round duct)

Loss = 150.3 ft. x (0.047 in wg /100 ft.)

Loss = 0.0706 in wg

The total static pressure required at fan discharge is the sum of the terminal operating

pressure and the loss in the duct work. Credit can be taken for the regain between the

first and last section of the duct.

From chart 7, p. 2-33 of Carrier Handbook with cfm of 1503.5 and equivalent circular

duct diameter = 17.5 in., velocity in the last section = 920 fpm.

Using 75% regain coefficient;

Regain = = 0.0658 in wg

Therefore, the total static pressure at fan discharge is;

• 8/8/2019 Chapter IV Ducting

7/24

= duct friction + terminal pressure regain

= 00706 + 0.15 0.0658

= 0.15 in wg

ZONE 2

Duct Sizing for Supply Air in Zone 2:

Total number of diffuser = 42

Percent of cfm =

Duct area entering section 1:

Duct area = percent of area times initial duct area (fan at section 1)

All areas are listed in Table 3.1.1

The Duct sizes can then be determined by using Carrier handbook, PP 2-36, Table 6.

Table 3.1.1 listed all the duct size.

The Additional Equivalent Length can be determining from Carrier handbook, PP 2-44,

Table 12.

Duct

Section

Air

Quantity

CFM

Capacity%

Area

%

Area

ft

Duct

Size Item

Length

(m)

Length

(ft)

Equiv.length

AHU2-A 50136.00 100.00 100 29.50 64 x 72 Duct Elbow 10.75 35.26 34.67

A-B 50136.00 100.00 100 29.50 64 x 72 Duct Elbow 10.7 35.096 34.67

B-C 40586.40 80.95 85.5 25.22 64 x 60

Series of

Elbow 7 22.96 33.67

C-D 31036.80 61.91 69 20.36 52 x 60

Series of

Elbow 4.2 13.776 28.67

• 8/8/2019 Chapter IV Ducting

8/24

D-E 22680.90 45.24 53 15.64 52 x 46

Series of

Elbow 4.7 15.416 26.5

E-F 14325.00 28.57 36.5 10.77 36 x 46 Elbow Duct 3.5 11.48 20

F-38 5969.10 11.91 18.5 5.46 30 x 28 Duct Elbow 6.6 21.648 16

B-1 9549.60 19.05 26 7.67 32 x 38 Elbow Duct 2.6 8.528 20

1-2 8355.90 16.67 24 7.08 32 x 34 Duct 4.5 14.76

2-3 7162.20 14.29 20.5 6.05 28 x 34 Duct 4.5 14.76

3-4 5968.50 11.90 18.5 5.46 28 x 30 Duct 4.5 14.76

4-5 4774.80 9.52 16.5 4.87 28 x 26 Duct 4.5 14.76

5-6 3581.10 7.14 11.5 3.39 20 x 26 Duct 4.5 14.76

6-7 2387.40 4.76 9 2.66 20 x 20 Duct 4.5 14.76

7-8 1193.70 2.38 3.5 1.03 10 x 16 Duct 4.5 14.76

C-9 9549.60 19.05 26 7.67 32 x 38 Elbow Duct 2.4 7.872 20

9-10 8355.90 16.67 24 7.08 32 x 34 Duct 4.5 14.76

10-11 7162.20 14.29 20.5 6.05 28 x 34 Duct 4.5 14.76

11-12 5968.50 11.90 18.5 5.46 28 x 30 Duct 4.5 14.76

12-13 4774.80 9.52 16.5 4.87 28 x 26 Duct 4.5 14.76

13-14 3581.10 7.14 11.5 3.39 20 x 26 Duct 4.5 14.76

14-15 2387.40 4.76 9 2.66 20 x 20 Duct 4.5 14.76

15-16 1193.70 2.38 3.5 1.03 10 x 16 Duct 4.5 14.76

D-17 8355.90 16.67 24 7.08 32 x 34 Elbow Duct 4.35 14.268 18

17-18 7162.20 14.29 20.5 6.05 28 x 34 Duct 4.5 14.76

18-19 5968.50 11.90 18.5 5.46 28 x 30 Duct 4.5 14.76

19-20 4774.80 9.52 16.5 4.87 28 x 26 Duct 4.5 14.76

20-21 3581.10 7.14 11.5 3.39 20 x 26 Duct 4.5 14.76

21-22 2387.40 4.76 9 2.66 20 x 20 Duct 4.5 14.76

22-23 1193.70 2.38 3.5 1.03 10 x 16 Duct 4.5 14.76

E-24 8355.90 16.67 24 7.08 32 x 34 Elbow Duct 8.14 26.6992 18

24-25 7162.20 14.29 20.5 6.05 28 x 34 Duct 4.5 14.76

25-26 5968.50 11.90 18.5 5.46 28 x 30 Duct 4.5 14.76

26-27 4774.80 9.52 16.5 4.87 28 x 26 Duct 4.5 14.76

27-28 3581.10 7.14 11.5 3.39 20 x 26 Duct 4.5 14.76

28-29 2387.40 4.76 9 2.66 20 x 20 Duct 4.5 14.76

29-30 1193.70 2.38 3.5 1.03 10 x 16 Duct 4.5 14.76

F-31 8355.90 16.67 24 7.08 32 x 34 Elbow Duct 3.6 11.808 18

31-32 7162.20 14.29 20.5 6.05 28 x 34 Duct 4.5 14.76

32-33 5968.50 11.90 18.5 5.46 28 x 30 Duct 4.5 14.76

33-34 4774.80 9.52 16.5 4.87 28 x 26 Duct 4.5 14.76

34-35 3581.10 7.14 11.5 3.39 20 x 26 Duct 4.5 14.76

35-36 2387.40 4.76 9 2.66 20 x 20 Duct 4.5 14.76

36-37 1193.70 2.38 3.5 1.03 10 x 16 Duct 4.5 14.76

• 8/8/2019 Chapter IV Ducting

9/24

38-39 4774.80 9.52 16.5 4.87 28 x 26 Duct 4.5 14.76

39-40 3581.10 7.14 11.5 3.39 20 x 26 Duct 4.5 14.76

40-41 2387.40 4.76 9 2.66 20 x 20 Duct 4.5 14.76

41-42 1193.70 2.38 3.5 1.03 10 x 16 Duct 4.45 14.596

TOTAL LENGTH 756.0072 288.18

The total friction loss in the duct work from fan to last terminal 42 is:

Loss = total equivalent length x friction rate

For the total equivalent length, it appears that the longer run is from AHU 2 to terminal

42: 211.04 + 174.18 = 385.22 ft.

Friction rate: using Vsupply = 1700 fpm, cfm = 50136, Fr = 0.032 (from chart 7, page 2-33

friction loss for round duct)

Loss = 385.22 ft. x (0.032 in wg /100 ft.)

Loss = 0.1387 in wgThe total static pressure required at fan discharge is the sum of the terminal operating

pressure and the loss in the duct work. Credit can be taken for the regain between the

first and last section of the duct.

From chart 7, p. 2-33 of Carrier Handbook with cfm of 1193.7 and equivalent circular

duct diameter = 13.7 in., velocity in the last section = 1220 fpm.

Using 75% regain coefficient;

Regain = = 0.0657 in wg

Therefore, the total static pressure at fan discharge is;

= duct friction + terminal pressure regain= 0.1387 + 0.15 0.0657

= 0.223 in wg

Duct Sizing for Return Air in Zone 2:

Total number of diffuser = 27

Percent of cfm =

Duct area entering section 1:

• 8/8/2019 Chapter IV Ducting

10/24

DuctSection

AirQuantity

CFM

Capacity

%

Area%

Areaft.

DuctSize

Item Length(m)

Length(ft)

Equiv.

Length

AHU 2 - 1 47533.5 100.00 100 31.69 68 x 72 Elbow Duct 15.55 51.004 36.33

1-2 45773 96.30 96.5 30.5868 x 72

series

Elbow 5.44 17.8432 36.33

2-3 44012.5 92.59 94.5 29.95 64 x 72 Duct 9 29.52

3-4 42242 88.87 91.5 29.00 64 x 72 Duct 9 29.52

4-5 40491.5 85.19 88.5 28.05 64 x 68 Duct 9 29.52

5-6 38731 81.48 86 27.25 64 x 68 Duct 9 29.52

6-7 36970.5 77.78 83 26.30 60 x 68 Duct 5.25 17.22

7-8 35210 74.07 80 25.35 60 x 60 Duct 5.25 17.228-A 26407.5 55.56 64 20.28 52 x 60 Duct Elbow 3.5 11.48 28

A-B 19365.5 40.74 49 15.53 52 x 46 Elbow Duct 6.95 22.796 28

B-C 12323.5 25.93 33.5 10.62 36 x 46 Duct 6.95 22.796

C-25 5281.5 11.11 17.5 5.55 36 x 24 Duct 6.95 22.796

8-9 7042 14.81 21.5 6.81 36 x 30 Duct 9 29.52

9-10 5281.5 11.11 17.5 5.55 36 x 24 Duct 9 29.52

10-11 3521 7.41 11.5 3.64 24 x 24 Duct 9 29.52

11-12 1760.5 3.70 7 2.22 16 x 24 Duct 9 29.52

A-13 7042 14.81 21.5 6.81 36 x 30 Elbow Duct 4.5 14.76 16

13-14 5281.5 11.11 17.5 5.55 36 x 24 Duct 9 29.52

14-15 3521 7.41 11.5 3.64 24 x 24 Duct 9 29.52

15-16 1760.5 3.70 7 2.22 16 x 24 Duct 9 29.52

B-17 7042 14.81 21.5 6.81 36 x 30 Elbow Duct 3 9.84 16

17-18 5281.5 11.11 17.5 5.55 36 x 24 Duct 9 29.52

18-19 3521 7.41 11.5 3.64 24 x 24 Duct 9 29.52

19-20 1760.5 3.70 7 2.22 16 x 24 Duct 9 29.52

C-21 7042 14.81 21.5 6.81 36 x 30 Elbow Duct 1.5 4.92 16

21-22 5281.5 11.11 17.5 5.55 36 x 24 Duct 9 29.52

22-23 3521 7.41 11.5 3.64 24 x 24 Duct 9 29.52

23-24 1760.5 3.70 7 2.22 16 x 24 Duct 9 29.52

25-26 3521 7.41 11.5 3.64 24 x 24 Duct 9 29.52

26-27 1760.5 3.70 7 2.22 16 x 24 Duct 9 29.52

TOTAL LENGTH 773.5552 176.66

• 8/8/2019 Chapter IV Ducting

11/24

The total friction loss in the duct work from fan to last terminal 27 is:

Loss = total equivalent length x friction rate

For the total equivalent length, it appears that the longer run is from AHU 2 to terminal

27: 109.83 + 128.66 = 238.5 ft.

Friction rate: using Vsupply = 1500 fpm, cfm = 47533.5, Fr = 0.028 (from chart 7, page 2-33 friction loss for round duct)

Loss = 238.5 ft. x (0.028 in wg /100 ft.)

Loss = 0.0668 in wg

The total static pressure required at fan discharge is the sum of the terminal operating

pressure and the loss in the duct work. Credit can be taken for the regain between the

first and last section of the duct.

From chart 7, p. 2-33 of Carrier Handbook with cfm of 1760.5 and equivalent circular

duct diameter = 21.3 in., velocity in the last section = 720 fpm.

Using 75% regain coefficient;

Regain = = 0.0812 in wgTherefore, the total static pressure at fan discharge is;

= duct friction + terminal pressure regain

= 0.0668 + 0.15 0.0812

= 0.1356 in wg

ZONE 3

Duct Sizing for Supply Air in Zone 3:

Total number of diffuser = 79

Percent of cfm =

Duct area entering section 1:

Duct area = percent of area times initial duct area (fan at section 1)

• 8/8/2019 Chapter IV Ducting

12/24

All areas are listed in Table 3.1.1

The Duct sizes can then be determined by using Carrier handbook, PP 2-36, Table 6.

Table 3.1.1 listed all the duct size.

The Additional Equivalent Length can be determining from Carrier handbook, PP 2-44,

Table 12.

Duct

Section

Air

Quantity

CFM

Capacity

%

Area

%

Area

ft

Duct

Size Item

Length

(m) Length (ft)

Equiv.

length

AHU 3 - A 60838.80 100.00 100 35.79 72 x 76 Duct Elbow 7.8 25.584 38

A-1 53907.80 88.61 91.5 32.75 68 x 76 series elbow 8 26.24 36.33

1-2 53137.70 87.34 90 32.21 68 x 68 series elbow 5.4 17.712 36

2-B 52367.59 86.08 89.5 32.03 68 x 68 series elbow 1.2 3.936 36

B-C 40815.94 67.09 73.5 26.31 68 x 56 series elbow 8.4 27.552 35

C-D 29264.29 48.10 56 20.04 52 x 56 series elbow 3.76 12.3328 29.56

D-E 16942.53 27.85 35.5 12.71 42 x 44 series elbow 8.6 28.208 24

E-68 2310.44 3.80 7 2.51 18 x 20 Duct Elbow 3.9 12.792 10

B-3 11551.65 18.99 26 9.31 36 x 38 Elbow Duct 2.4 7.872 19.83

3-4 10781.54 17.72 25 8.95 36 x 36 Duct 4 13.12

4-5 10011.43 16.46 23 8.23 34 x 36 Duct 4.2 13.776

5-6 9241.32 15.19 21.5 7.69 34 x 34 Duct 4.15 13.612

6-7 8471.21 13.92 20.5 7.34 32 x 34 Duct 4 13.12

7-8 7701.1 12.66 19.5 6.98 32 x 32 Duct 4.2 13.776

8-9 6930.99 11.39 18.5 6.62 30 x 32 Duct 4.15 13.612

9-10 6160.88 10.13 16.5 5.91 30 x 30 Duct 4 13.12

10-11 5390.77 8.86 14.5 5.19 26 x 30 Duct 4.2 13.776

11-12 4620.66 7.59 13 4.65 26 x 26 Duct 4.15 13.612

12-13 3850.55 6.33 10.5 3.76 26 x 24 Duct 4 13.12

13-14 3080.44 5.06 9 3.22 20 x 24 Duct 4.2 13.776

14-15 2310.33 3.80 7 2.51 20 x 18 Duct 4.15 13.612

15-16 1540.22 2.53 5.5 1.97 16 x 18 Duct 4 13.12

16-17 770.11 1.27 2 0.72 6 x 18 Duct 4.2 13.776

C-18 11551.65 18.99 26 9.31 36 x 38 Elbow Duct 5.87 19.2536 19.83

18-19 10781.54 17.72 25 8.95 36 x 36 Duct 4 13.12

19-20 10011.43 16.46 23 8.23 34 x 36 Duct 4.2 13.776

20-21 9241.32 15.19 21.5 7.69 34 x 34 Duct 4.15 13.612

• 8/8/2019 Chapter IV Ducting

13/24

21-22 8471.21 13.92 20.5 7.34 32 x 34 Duct 4 13.12

22-23 7701.1 12.66 19.5 6.98 32 x 32 Duct 4.2 13.776

23-24 6930.99 11.39 18.5 6.62 30 x 32 Duct 4.15 13.612

24-25 6160.88 10.13 16.5 5.91 30 x 30 Duct 4 13.12

25-26 5390.77 8.86 14.5 5.19 26 x 30 Duct 4.2 13.77626-27 4620.66 7.59 13 4.65 26 x 26 Duct 4.15 13.612

27-28 3850.55 6.33 10.5 3.76 26 x 24 Duct 4 13.12

28-29 3080.44 5.06 9 3.22 20 x 24 Duct 4.2 13.776

29-30 2310.33 3.80 7 2.51 20 x 18 Duct 4.15 13.612

30-31 1540.22 2.53 5.5 1.97 16 x 18 Duct 4 13.12

31-32 770.11 1.27 2 0.72 6 x 18 Duct 4.2 13.776

D-33 12321.76 20.25 27 9.66 36 x 38 Elbow Duct 4.7 15.416 19.83

33-34 11551.65 18.99 26 9.31 36 x 38 Duct 6.4 20.992

34-35 10781.54 17.72 25 8.95 36 x 36 Duct 4.5 14.76

35-36 10011.43 16.46 23 8.23 34 x 36 Duct 4.5 14.76

36-37 9241.32 15.19 21.5 7.69 34 x 34 Duct 3.4 11.152

37-38 8471.21 13.92 20.5 7.34 32 x 34 Duct 4.5 14.76

38-39 7701.1 12.66 19.5 6.98 32 x 32 Duct 4.5 14.76

39-40 6930.99 11.39 18.5 6.62 30 x 32 Duct 3.4 11.152

40-41 6160.88 10.13 16.5 5.91 30 x 30 Duct 4.5 14.76

41-42 5390.77 8.86 14.5 5.19 26 x 30 Duct 4.5 14.76

42-43 4620.66 7.59 13 4.65 26 x 26 Duct 3.4 11.152

43-44 3850.55 6.33 10.5 3.76 26 x 24 Duct 4.5 14.76

44-45 3080.44 5.06 9 3.22 20 x 24 Duct 4.5 14.76

45-46 2310.33 3.80 7 2.51 20 x 18 Duct 3.4 11.152

46-47 1540.22 2.53 5.5 1.97 16 x 18 Duct 4.5 14.76

47-48 770.11 1.27 2 0.72 6 x 18 Duct 4.5 14.76

E-49 14632.09 24.05 31.5 11.27 40 x 40 Elbow Duct 0.8 2.624 21.56

49-50 13861.98 22.78 30.5 10.92 40 x 40 Duct 4.5 14.76

50-51 13091.89 21.52 29.5 10.56 40 x 38 Duct 4.5 14.76

51-52 12321.76 20.25 27 9.66 36 x 38 Duct Elbow 4.2 13.776 19.83

52-53 11551.65 18.99 26 9.31 36 x 38 Duct 6.3 20.664

53-54 10781.54 17.72 25 8.95 36 x 36 Duct 4.5 14.76

54-55 10011.43 16.46 23 8.23 34 x 36 Duct 4.5 14.76

55-56 9241.32 15.19 21.5 7.69 34 x 34 Duct 3.4 11.152

56-57 8471.21 13.92 20.5 7.34 32 x 34 Duct 4.5 14.76

57-58 7701.1 12.66 19.5 6.98 32 x 32 Duct 4.5 14.76

58-59 6930.99 11.39 18.5 6.62 30 x 32 Duct 3.4 11.152

• 8/8/2019 Chapter IV Ducting

14/24

59-60 6160.88 10.13 16.5 5.91 30 x 30 Duct 4.5 14.76

60-61 5390.77 8.86 14.5 5.19 26 x 30 Duct 4.5 14.76

61-62 4620.66 7.59 13 4.65 26 x 26 Duct 3.4 11.152

62-63 3850.55 6.33 10.5 3.76 26 x 24 Duct 4.5 14.76

63-64 3080.44 5.06 9 3.22 20 x 24 Duct 4.5 14.7664-65 2310.33 3.80 7 2.51 20 x 18 Duct 3.4 11.152

65-66 1540.22 2.53 5.5 1.97 16 x 18 Duct 4.5 14.76

66-67 770.11 1.27 2 0.72 6 x 18 Duct 4.5 14.76

68-69 1540.22 2.53 5.5 1.97 10 x 12 Duct 4.5 14.76

69-70 770.11 1.27 2 0.72 6 x 10 Duct 4.5 14.76

A-H 6930.99 11.39 18.5 6.62 30 x 32 Duct Elbow 4.4 14.432

H-71 6930.99 11.39 18.5 6.62 30 x 32 series elbow 4.85 15.908

71-72 6160.88 10.13 16.5 5.91 30 x 30 series elbow 5.6 18.368 16

72-73 5390.77 8.86 14.5 5.19 26 x 30 series elbow 5 16.4 15.625

73-74 4620.66 7.59 13 4.65 26 x 26 series elbow 5.8 19.024 13.875

74-75 3850.55 6.33 10.5 3.76 26 x 24 series elbow 5.9 19.352 13.75

75-76 3080.44 5.06 9 3.22 20 x 24 series elbow 6.25 20.5 11

76-77 2310.33 3.80 7 2.51 20 x 18 series elbow 5.45 17.876 10

77-78 1540.22 2.53 5.5 1.97 16 x 18 series elbow 5 16.4 10

78-79 770.11 1.27 2 0.72 6 x 18 series elbow 4.86 15.9408 8

TOTAL LENGTH 1250.4672 444.02

The total friction loss in the duct work from fan to last terminal 79 is:

Loss = total equivalent length x friction rate

For the total equivalent length, it appears that the longer run is from AHU 3 to terminal

67: 399.64 + 276.28 = 675.92 ft.

Friction rate: using Vsupply = 1700 fpm, cfm = 60838.8, Fr = 0.0325 (from chart 7, page

2-33 friction loss for round duct)

Loss = 675.92 ft. x (0.0325 in wg /100 ft.)

Loss = 0.22 in wg

The total static pressure required at fan discharge is the sum of the terminal operating

pressure and the loss in the duct work. Credit can be taken for the regain between the

first and last section of the duct.

From chart 7, p. 2-33 of Carrier Handbook with cfm of 770.11 and equivalent circular

duct diameter = 11.5 in., velocity in the last section = 1110 fpm.

Using 75% regain coefficient;

Regain = = 0.0777 in wg

Therefore, the total static pressure at fan discharge is;

• 8/8/2019 Chapter IV Ducting

15/24

= duct friction + terminal pressure regain

= 0.22 + 0.15 0.0777

= 02923 in wg

Duct Sizing for Return Air in Zone 3:

Total number of diffuser = 27

Percent of cfm =

Duct area entering section 1:

Duct

Section

Air

Quantity

CFM

Capacity

%

Area

%

Area

ft.

Duct

SizeItem

Length

(m)

Length

(ft)

Equiv.

Length

AHU 3 - 1 57253.8 100.00 100 38.17 68 x 88 Elbow 32 104.96 39.44

1-2 55133.3 96.30 96.5 36.83 64 x 88 Duct 8.2 26.896

2-3 53012.8 92.59 94.5 36.07 64 x 88 Duct 8.2 26.896

3-4 50892.3 88.89 91.5 34.93 64 x 84 Duct 8.2 26.896

4-5 48771.8 85.19 88.5 33.78 64 x 80 Duct 8.2 26.896

5-6 46651.3 81.48 86 32.83 64 x 80 Duct 8.2 26.896

6-A 44530.8 77.78 83 31.68 60 x 80 Elbow Duct 12.6 41.328 40.33

A-15 27566.8 48.15 56 21.38 60 x 56 Duct Elbow 12.7 41.656 30.33

A-7 16964 29.63 37.5 14.31 42 x 54 Elbow Duct 3.9 12.792 29

7-8 14843.5 25.93 33.5 12.79 42 x 48 Duct 8.2 26.896

8-9 12723 22.22 29.5 11.26 42 x 42 Duct 8.2 26.896

9-10 10602.5 18.52 26 9.92 38 x 42 Duct 8.2 26.896

10-11 8482 14.81 21.5 8.21 38 x 34 Duct 8.2 26.896

11-12 6361.5 11.11 17.5 6.68 30 x 34 Duct 8.2 26.896

12-13 4241 7.41 11.5 4.39 30 x 24 Duct 8.2 26.896

13-14 2120.5 3.70 7 2.67 18 x 24 Duct 8.2 26.896

15-16 25446 44.44 52 19.85 56 x 56 Duct 4.5 14.76

16-17 23325.5 40.74 49 18.70 52 x 56 Duct 7.9 25.912

17-18 21205 37.04 45 17.18 52 x 50 Duct 4.5 14.76

• 8/8/2019 Chapter IV Ducting

16/24

18-19 19084.5 33.33 41 15.65 48 x 50 Duct 7.9 25.912

19-20 16964 29.63 37.5 14.31 42 x 54 Duct 4.5 14.76

20-21 14843.5 25.93 33.5 12.79 42 x 48 Duct 7.9 25.912

21-22 12723 22.22 29.5 11.26 42 x 42 Duct 4.5 14.76

22-23 10602.5 18.52 26 9.92 38 x 42 Duct 7.9 25.912

23-24 8482 14.81 21.5 8.21 38 x 34 Duct 4.5 14.76

24-25 6361.5 11.11 17.5 6.68 30 x 34 Duct 4.5 14.76

25-26 4241 7.41 11.5 4.39 30 x 24 Duct 4.5 14.76

26-27 2120.5 3.70 7 2.67 18 x 24 Duct 4.5 14.76

TOTAL LENGTH 745.216 139.1

The total friction loss in the duct work from fan to last terminal 27 is:

Loss = total equivalent length x friction rate

For the total equivalent length, it appears that the longer run is from AHU 3 to terminal

27: 166.22 + 110.06 = 276.28 ft.

Friction rate: using Vsupply = 1500 fpm, cfm = 57253.8, Fr = 0.025 (from chart 7, page 2-

33 friction loss for round duct)

Loss = 276.28 ft. x (0.025 in wg /100 ft.)

Loss = 0.069 in wg

The total static pressure required at fan discharge is the sum of the terminal operating

pressure and the loss in the duct work. Credit can be taken for the regain between the

first and last section of the duct.

From chart 7, p. 2-33 of Carrier Handbook with cfm of 2120.5 and equivalent circular

duct diameter = 22.6 in., velocity in the last section = 780 fpm.

Using 75% regain coefficient;

Regain = = 0.0777 in wgTherefore, the total static pressure at fan discharge is;

= duct friction + terminal pressure regain

= 0.069 + 0.15 0.0777

= 0.142 in wg

ZONE 4

Duct Sizing for Supply Air in Zone 4:

Total number of diffuser = 45

• 8/8/2019 Chapter IV Ducting

17/24

Percent of cfm =

Duct area entering section 1:

Duct area = percent of area times initial duct area (fan at section 1)

All areas are listed in Table 3.1.1

The Duct sizes can then be determined by using Carrier handbook, PP 2-36, Table 6.

Table 3.1.1 listed all the duct size.

The Additional Equivalent Length can be determining from Carrier handbook, PP 2-44,

Table 12.

Duct

Section

Air

Quantity

CFM

Capacity

%

Area

%

Area

ft

Duct

SizeItem

Length

(m)Length(ft)

Equiv.

length

AHU 4 - 1 26131 100.00 100 15.37 48 x 50 Duct 8.88 29.12641-2 25550.3 97.78 98 15.06 46 x 50 Duct 4.5 14.76

2-3 24969.6 95.56 96.5 14.83 46 x 50 Duct 4.5 14.76

3-4 24388.9 93.33 94.5 14.52 46 x 50 Duct 4.5 14.76

4-A 23808.2 91.11 93 14.29 46 x 48 Elbow Duct 6 19.68 25

A-B 19162.6 73.33 79 12.14 42 x 44 Duct 4.5 14.76

B-C 14517 55.55 64 9.84 42 x 36 Duct 4.5 14.76

C-D 9871.4 37.78 46 7.07 34 x 32 Duct Elbow 3.5 11.48 18

D-E 9290.7 35.55 44 6.76 32 x 32 Duct 4.5 14.76

E-F 8710 33.33 41 6.30 32 x 30 Duct 4.5 14.76

F-G 8129.3 31.11 39 5.99 30 x 30 Duct 4.5 14.76

G-H 6387.2 24.44 31.5 4.84 28 x 28 Duct 4.5 14.76

H-I 4645.1 17.78 25 3.84 24 x 28 Duct 4.5 14.76

I-J 2903 11.11 17.5 2.69 24 x 18 Duct 4.5 14.76

A-5 4645.6 17.78 25 3.84 24 x 28 Elbow Duct 1.5 4.92 13

5-6 4064.9 15.56 23 3.54 20 x 28 Duct 4.5 14.76

• 8/8/2019 Chapter IV Ducting

18/24

6-7 3484.2 13.33 19.5 3.00 20 x 24 Duct 4.5 14.76

7-8 2903.5 11.11 17.5 2.69 18 x 24 Duct 4.5 14.76

8-9 2322.8 8.89 14.5 2.23 18 x 20 Duct 4.5 14.76

9-10 1742.1 6.67 11.5 1.77 14 x 20 Duct 4.5 14.76

10-11 1161.4 4.44 7 1.08 14 x 12 Duct 4.5 14.7611-12 580.7 2.22 3.5 0.54 8 x 12 Duct 4.5 14.76

B-13 4645.6 17.78 25 3.84 24 x 28 Elbow Duct 1.5 4.92 13

13-14 4064.9 15.56 23 3.54 20 x 28 Duct 4.5 14.76

14-15 3484.2 13.33 19.5 3.00 20 x 24 Duct 4.5 14.76

15-16 2903.5 11.11 17.5 2.69 18 x 24 Duct 4.5 14.76

16-17 2322.8 8.89 14.5 2.23 18 x 20 Duct 4.5 14.76

17-18 1742.1 6.67 11.5 1.77 14 x 20 Duct 4.5 14.76

18-19 1161.4 4.44 7 1.08 14 x 12 Duct 4.5 14.76

19-20 580.7 2.22 3.5 0.54 8 x 12 Duct 4.5 14.76

C-21 4645.6 17.78 25 3.84 24 x 28 Elbow Duct 1.5 4.92 13

21-22 4064.9 15.56 23 3.54 20 x 28 Duct 4.5 14.76

22-23 3484.2 13.33 19.5 3.00 20 x 24 Duct 4.5 14.76

23-24 2903.5 11.11 17.5 2.69 18 x 24 Duct 4.5 14.76

24-25 2322.8 8.89 14.5 2.23 18 x 20 Duct 4.5 14.76

25-26 1742.1 6.67 11.5 1.77 14 x 20 Duct 4.5 14.76

26-27 1161.4 4.44 7 1.08 14 x 12 Duct 4.5 14.76

27-28 580.7 2.22 3.5 0.54 8 x 12 Duct 4.5 14.76

D-29 580.7 2.22 3.5 0.54 8 x 12 Elbow Duct 1 3.28 5

E-30 580.7 2.22 3.5 0.54 8 x 12 Elbow Duct 1 3.28 5

F-31 580.7 2.22 3.5 0.54 8 x 12 Elbow Duct 1 3.28 5

G-32 1742.1 6.67 11.5 1.77 14 x 20 Elbow Duct 1 3.28 8

32-33 1161.4 4.44 7 1.08 14 x 12 Duct 4.5 14.76

33-34 580.7 2.22 3.5 0.54 8 x 12 Duct 4.5 14.76

H-35 1742.1 6.67 11.5 1.77 14 x 20 Elbow Duct 1 3.28 8

35-36 1161.4 4.44 7 1.08 14 x 12 Duct 4.5 14.76

36-37 580.7 2.22 3.5 0.54 8 x 12 Duct 4.5 14.76

I-38 1742.1 6.67 11.5 1.77 14 x 20 Elbow Duct 1 3.28 8

38-39 1161.4 4.44 7 1.08 14 x 12 Duct 4.5 14.76

39-40 580.7 2.22 3.5 0.54 8 x 12 Duct 4.5 14.76

J-41 1742.1 6.67 11.5 1.77 14 x 20 Elbow Duct 1 3.28 8

41-42 1161.4 4.44 7 1.08 14 x 12 Duct 4.5 14.76

42-43 580.7 2.22 3.5 0.54 8 x 12 Duct 4.5 14.76

J-44 1160.9 4.44 7 1.08 14 x 12 Duct Elbow 5.5 18.04 8

• 8/8/2019 Chapter IV Ducting

19/24

44-45 580.7 2.22 3.5 0.54 8 x 12 Duct 4.5 14.76

TOTAL LENGTH 721.2064 137

The total friction loss in the duct work from fan to last terminal 45 is:

Loss = total equivalent length x friction rateFor the total equivalent length, it appears that the longer run is from AHU 4 to terminal

43: 260.33 + 51 = 311.33 ft.

Friction rate: using Vsupply = 1700 fpm, cfm = 26131, Fr = 0.056 (from chart 7, page 2-33

friction loss for round duct)

Loss = 311.33 ft. x (0.056 in wg /100 ft.)

Loss = 0.1743 in wg

The total static pressure required at fan discharge is the sum of the terminal operating

pressure and the loss in the duct work. Credit can be taken for the regain between the

first and last section of the duct.

From chart 7, p. 2-33 of Carrier Handbook with cfm of 580.7 and equivalent circular duct

diameter = 10.7 in., velocity in the last section = 940 fpm.

Using 75% regain coefficient;

Regain = = 0.09405 in wg

Therefore, the total static pressure at fan discharge is;

= duct friction + terminal pressure regain

= 0.1743 + 0.15 0.09405

= 0.230 in wg

Duct Sizing for Return Air in Zone 4:

Total number of diffuser = 18

Percent of cfm =

Duct area entering section 1:

• 8/8/2019 Chapter IV Ducting

20/24

Duct

Section

Air

Quantity

CFM

Capacity

%

Area

%

Area

ft.

Duct

SizeItem

Length

(m)

Length

(ft)

Equiv.

Length

AHU 4 - A 24706 100.00 100 16.47 50 x 50 Duct 0.95 3.116

A-1 20588.33 83.33 87 14.33 44 x 50 Elbow Duct 3.88 12.7264 27

1-B 19215.78 77.78 83 13.67 44 x 48 Duct Elbow 8.82 28.9296 24B-C 15098.11 61.11 68 11.20 42 x 42 Duct 4.5 14.76

C-D 9607.89 38.89 47 7.74 30 x 40 Duct 4.5 14.76

D-15 5490.22 22.22 29.5 4.86 30 x 26 Duct 4 13.12

A-2 4117.67 16.67 24 3.95 24 x 26 Elbow Duct 5 16.4 14

2-3 2745.11 11.11 17.5 2.88 22 x 20 Duct 9 29.52

3-4 1372.56 5.56 10.6 1.75 14 x 20 Duct 9 29.52

B-5 4117.67 16.67 24 3.95 24 x 26 Elbow Duct 8.82 28.9296 14

5-6 2745.11 11.11 17.5 2.88 22 x 20 Duct 9 29.52

6-7 1372.56 5.56 10.6 1.75 14 x 20 Duct 9 29.52

C-8 5490.22 22.22 29.5 4.86 30 x 26 Elbow Duct 4.32 14.1696 15

8-9 4117.67 16.67 24 3.95 24 x 26 Duct 9 29.52

9-10 2745.11 11.11 17.5 2.88 22 x 20 Duct 9 29.52

10-11 1372.56 5.56 10.6 1.75 14 x 20 Duct 9 29.52

D-12 4117.67 16.67 24 3.95 24 x 26 Elbow Duct 8.82 28.9296 14

12-13 2745.11 11.11 17.5 2.88 22 x 20 Duct 9 29.52

13-14 1372.56 5.56 10.6 1.75 14 x 20 Duct 9 29.52

15-16 4117.67 16.67 24 3.95 24 x 26 Duct Elbow 9.32 30.5696 14

16-17 2745.11 11.11 17.5 2.88 22 x 20 Duct Elbow 10 32.8 8

17-18 1372.56 5.56 10.6 1.75 14 x 20 Duct 9 29.52

TOTAL LENGTH 534.4104 130

The total friction loss in the duct work from fan to last terminal 18 is:

Loss = total equivalent length x friction rate

For the total equivalent length, it appears that the longer run is from AHU 4 to terminal

18: 55.03 + 73 = 128.03 ft.

Friction rate: using Vsupply = 1500 fpm, cfm = 24706, Fr = 0.0435 (from chart 7, page 2-33 friction loss for round duct)

Loss = 128.03 ft. x (0.0435 in wg /100 ft.)

Loss = 0.0557 in wg

The total static pressure required at fan discharge is the sum of the terminal operating

pressure and the loss in the duct work. Credit can be taken for the regain between the

first and last section of the duct.

• 8/8/2019 Chapter IV Ducting

21/24

From chart 7, p. 2-33 of Carrier Handbook with cfm of 1372.56 and equivalent circular

duct diameter = 18.2 in., velocity in the last section = 720 fpm.

Using 75% regain coefficient;

Regain = = 0.0812 in wg

Therefore, the total static pressure at fan discharge is;= duct friction + terminal pressure regain

= 0.0557 + 0.15 0.0812

= 0.1245 in wg

ZONE 5

Duct Sizing for Supply Air in Zone 5:

Total number of diffuser = 25

Percent of cfm =

Duct area entering section 1:

Duct area = percent of area times initial duct area (fan at section 1)

All areas are listed in Table 3.1.1

The Duct sizes can then be determined by using Carrier handbook, PP 2-36, Table 6.

Table 3.1.1 listed all the duct size.

The Additional Equivalent Length can be determining from Carrier handbook, PP 2-44,

Table 12.

Duct

Section

Air

Quantity

CFM

Capacity

Area

%

Area

ft

Duct

SizeItem

Length

(m)

Length

(ft)

Equiv.

• 8/8/2019 Chapter IV Ducting

22/24

% length

AHU 5 - A 21216.43 100.00 100 12.48 44 x 44 Elbow 1.6 5.248

A-10 16124.47 76.00 81 10.11 36 x 44 Duct 4.5 14.76

10-16 11032.51 52.00 60 7.49 36 x 32 Duct 4.5 14.76

16-21 6789.21 32.00 40 4.99 24 x 32 Duct 4.5 14.7621-25 2545.91 12.00 18.5 2.31 24 x 16 Duct 4.5 14.76

A-2 1697.32 8.00 13 1.62 16 x 16 Elbow Duct 4.5 14.76 7.67

2-1 848.66 4.00 7 0.87 8 x 16 Duct 4.5 14.76

A-3 3394.64 16.00 23 2.87 20 x 22 Elbow Duct 4.5 14.76 13.2

3-4 2545.98 12.00 18.5 2.31 20 x 18 Duct 4.5 14.76

4-5 1697.32 8.00 13 1.62 14 x 18 Duct 4.5 14.76

5-6 848.66 4.00 7 0.87 14 x 10 Duct 4.5 14.76

10-9 2545.98 12.00 18.5 2.31 20 x 18 Duct 4.5 14.76

9-8 1697.32 8.00 13 1.62 14 x 18 Duct 4.5 14.76

8-7 848.66 4.00 7 0.87 14 x 10 Duct 4.5 14.76

10-11 1697.32 8.00 13 1.62 14 x 18 Duct 4.5 14.76

11-12 848.66 4.00 7 0.87 14 x 10 Duct 4.5 14.76

16-17 848.66 4.00 7 0.87 14 x 10 Duct 4.5 14.76

16-15 2545.98 12.00 18.5 2.31 20 x 18 Duct 4.5 14.76

15-14 1697.32 8.00 13 1.62 14 x 18 Duct 4.5 14.76

14-13 848.66 4.00 7 0.87 14 x 10 Duct 4.5 14.76

21-22 848.66 4.00 7 0.87 14 x 10 Duct 4.5 14.76

21-20 2545.98 12.00 18.5 2.31 20 x 18 Duct 4.5 14.76

20-19 1697.32 8.00 13 1.62 14 x 18 Duct 4.5 14.76

19-18 848.66 4.00 7 0.87 14 x 10 Duct 4.5 14.76

25-24 1697.32 8.00 13 1.62 14 x 18 Duct 4.5 14.76

24-23 848.66 4.00 7 0.87 14 x 10 Duct 4.5 14.76

TOTAL LENGTH 374.248 20.87

The total friction loss in the duct work from fan to last terminal 25 is:

Loss = total equivalent length x friction rate

For the total equivalent length, it appears that the longer run is from AHU 5 to terminal

25: 28.5 ft.

Friction rate: using Vsupply = 1700 fpm, cfm = 21216.3, Fr = 0.064 (from chart 7, page 2-

33 friction loss for round duct)

Loss = 28.5 ft. x (0.064 in wg /100 ft.)

Loss = 0.01824 in wg

• 8/8/2019 Chapter IV Ducting

23/24

The total static pressure required at fan discharge is the sum of the terminal operating

pressure and the loss in the duct work. Credit can be taken for the regain between the

first and last section of the duct.

From chart 7, p. 2-33 of Carrier Handbook with cfm of 848.66 and equivalent circular

duct diameter = 12.9 in., velocity in the last section = 1000 fpm.Using 75% regain coefficient;

Regain = = 0.0886 in wg

Therefore, the total static pressure at fan discharge is;

= duct friction + terminal pressure regain

= 0.01824 + 0.15 0.0886

= 0.15 in wg

Duct Sizing for Return Air in Zone 5:

Total number of diffuser = 12

Percent of cfm =

Duct area entering section 1:

Duct

Section

Air

Quantity

CFM

Capacity

%

Area

%

Area

ft.

Duct

Size

Item

Length

(m)

Length

(ft)

Equiv.

LengthAHU 5 - A 20766.43 100.00 100 13.84 46 x 46 Duct Elbow 16.8 55.104 25

A-B 19035.89 91.67 94 13.01 44 x 46 Duct 4.66 15.2848

B-C 15574.82 75.00 80.5 11.14 44 x 40 Duct 4.66 15.2848

C-D 12113.75 58.33 65.6 9.08 36 x 40 Duct 4.66 15.2848

D-7 10383.22 50.00 58 8.03 34 x 38 Duct Elbow 14 45.92 20

7-E 8652.68 41.67 50 6.92 30 x 36 Duct Elbow 12.86 42.1808 16

• 8/8/2019 Chapter IV Ducting

24/24

E-F 6922.14 33.33 41 5.67 30 x 30 Duct 5.56 18.2368

F-G 5191.61 25.00 32.5 4.50 24 x 30 Duct 5.56 18.2368

G-11 3461.07 16.67 24 3.32 24 x 22 Duct Elbow 7.96 26.1088 12

A-1 1730.54 8.33 13 1.80 14 x 22 Elbow Duct 7.8 25.584 10.5

B-2 3461.07 16.67 24 3.32 24 x 22 Elbow Duct 4.5 14.76 12

2-3 1730.54 8.33 13 1.80 14 x 22 Duct 9 29.52

C-4 3461.07 16.67 24 3.32 24 x 22 Elbow Duct 1.2 3.936 12

4-5 1730.54 8.33 13 1.80 14 x 22 Duct 9 29.52

D-6 1730.54 8.33 13 1.80 14 x 22 Elbow Duct 6.9 22.632 10.5

E-8 1730.54 8.33 13 1.80 14 x 22 Elbow Duct 6.1 20.008 10.5

F-9 1730.54 8.33 13 1.80 14 x 22 Elbow Duct 4.87 15.9736 10.5

G-10 1730.54 8.33 13 1.80 14 x 22 Elbow Duct 3.64 11.9392 10.5

11-12 1730.54 8.33 13 1.80 14 x 22 Duct 9 29.52

TOTAL LENGTH 455.0344 149.5

The total friction loss in the duct work from fan to last terminal 12 is:

Loss = total equivalent length x friction rate

For the total equivalent length, it appears that the longer run is from AHU 5 to terminal

12: 85.95 ft. + 73 = 158.95 ft.

Friction rate: using Vsupply = 1500 fpm, cfm = 20766.43, Fr = 0.04 (from chart 7, page 2-

33 friction loss for round duct)

Loss = 158.95 ft. x (0.04 in wg /100 ft.)

Loss = 0.0636 in wg

The total static pressure required at fan discharge is the sum of the terminal operating

pressure and the loss in the duct work. Credit can be taken for the regain between the

first and last section of the duct.

From chart 7, p. 2-33 of Carrier Handbook with cfm of 1730.54 and equivalent circular

duct diameter = 19.1 in., velocity in the last section = 880 fpm.

Using 75% regain coefficient;

Regain = = 0.0692 in wg

Therefore, the total static pressure at fan discharge is;

= duct friction + terminal pressure regain

= 0.0636 + 0.15 0.0692

= 0.144 in wg

Recommended