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Disclaimer: The author and ASHRAE do not warrant that the information on this spreadsheet is free of errors.

provided as is without warranty of any kind, either expressed or implied. The entire risk as to the quality and pe

information is with you. In no event will ASHRAE be liable to you for any damages, including without limitation a

savings, or other incidental or consequential damages arising out of the use or inability to use this information.

Copyright 2009 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

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DUCT SIZE CALCULATION SPREADSHEET Run macro "friction factor"

Project system-zone

shaded cell: user imput, cell or col

Reynolds Re = 8.56*D*V e= 0.0003

D=(1.3(a*b)^.625)/(a+b)^.25 rho= 0.0763V=Q/((Pi*D^2/4)/144) dp100(target) = 0.09

Colbrook 1/f^.5 = -2*log(12*e/3.7/D+2.51/Re/f^.5) Zone air flow = 1575

dp = (12*f*L*rho*(V/1097)^2)/D Zone outdoor air = 250

All data below calculated by macro except fixture co

brcountmax = 12 This macro will clear the contents of all calculated ce

duct leg airflow Q height a width b dia D V Re L duct dp

cfm in in in fpm ft iw

1 1575 14 17.0 16.8 1018 146745 20 0.017

2 1185 12 16.0 15.1 952 123097 15 0.013

3 985 12 14.0 14.2 901 109185 22 0.018

4 535 10 10.0 10.9 821 76809 8 0.008

5 385 10 8.0 9.8 741 61894 12 0.011

6 85 0 0.0 6.0 433 22234 20 0.013

7 72 0 0.0 6.0 364 18705 20 0.009

8 324 10 7.0 9.1 716 55799 12 0.011

9 450 10 9.0 10.4 768 68136 8 0.007

10 829 12 12.0 13.1 883 99140 22 0.019

11 997 12 14.0 14.2 912 110505 15 0.013

12 1325 14 15.0 15.8 968 131290 20 0.017

0.155

Template HP1, zone 1

formulas: fixed parameters (user input)

The macro "newductsize" computes duct diamter for a given cfm based on equal friction, us

Therefore the duct diameters and widths shown on sheet two are not rounded to the neares

diameter and width will be rounded to achievable dimensions before calculating the final du

Cell C29) must be the total number of duct segments calculated on sheet 2 in "newductsize"

macro to compute duct dp using the equation above. This macro will also compute fitting lo

input by the user from manufacturers data. The user may input C or dp for up to seven fixtu

input for each segment in the cells indicated by coda - codd below. At least one coda must

To run this macro: First input cfm, desired duct height, and segment length into the macro "

roughness e, air density rho, target dp100 (see below), zone supply air flow and zone outdo

segments "subcountmax" in the indicated cell. If duct height is input as zero, then the macro

rectangular. Run macro "newductsize" which will calculate both supply duct and return duct

number of supply duct segments input, with a return duct segment calculated for each suppl

user may instead input return segment cfm and height.

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umn

code Fixtures Fixture C dp

1 fan out 0.72

2 el 0.11

3 tee thru 0.044 tee branch 0.8

5 fan in 0.3

6 diffuser 0.04

7 ret grille 0.03

es, which are input by the user

lls. The fixture loss input cells, N32 - Q100 will not be cleared

dp/100' vdp fixdp systotdp count

iw/100' iw iw iw coda codb codc codd

0.084 0.066 0.057 0.074 1 2 3 12.000

0.085 0.057 0.002 0.015 3 12.000

0.083 0.051 0.008 0.026 3 2 11.000

0.096 0.043 0.039 0.047 4 2 10.000

0.091 0.035 0.001 0.012 3 11.000

0.063 0.012 0.050 0.062 4 6 13.000

0.046 0.008 0.031 0.041 7 3 2 13.000

0.093 0.032 0.001 0.012 3 12.000

0.090 0.037 0.030 0.037 4 11.000

0.088 0.049 0.007 0.027 3 2 11.000

0.085 0.053 0.002 0.015 3 11.000

0.083 0.059 0.027 0.043 5 3 2 12.000

0.256 0.411

fixture type, C, and dp input by user

fixture C or dp

fixture library

ing the delta p per 100' [dp100(target] input on this sheet in cell I9.

whole inch. When running the macro "friction factor", the duct

t velocity and friction loss. The parameter "brcountmax" (Sheet 1,

. Segment length, input on sheet 2, is used by the friction factor

ss based on either fitting "C" values from ASHRAE (Idlechik) or dp

es (Sheet 1, Cells M5 to N11), and up to four fixture codes may be

be input for each duct leg.

ewductsize" on sheet two, in the columns indicated. Input

r air on Sheet 1 Input the maximum number of supply duct

will assume that the duct segment will be round duct, not

iameter and width for each segment input, up to the maximum

y duct segment. If "return segments" is input greater than zero, the

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f' fact fact1 diff dpfixa dpfixb dpfixc dpfixd

iw iw iw iw

0.0180 7.4636 7.4637 -7.5E-05 0.0473 0.0072 0.0026 0.0000

0.0186 7.3389 7.3390 -5.1E-05 0.0023 0.0000 0.0000 0.0000

0.0190 7.2559 7.2559 -7.7E-05 0.0021 0.0057 0.0000 0.0000

0.0204 6.9962 6.9962 7.01E-05 0.0342 0.0047 0.0000 0.0000

0.0213 6.8467 6.8466 9.49E-05 0.0014 0.0000 0.0000 0.0000

0.0266 6.1363 6.1362 7.72E-05 0.0095 0.0400 0.0000 0.0000

0.0275 6.0258 6.0258 8.3E-05 0.0300 0.0003 0.0009 0.0000

0.0218 6.7715 6.7715 5.77E-05 0.0013 0.0000 0.0000 0.0000

0.0209 6.9154 6.9153 6.58E-05 0.0299 0.0000 0.0000 0.0000

0.0194 7.1833 7.1834 -4.7E-05 0.0020 0.0054 0.0000 0.0000

0.0190 7.2627 7.2627 -8E-05 0.0021 0.0000 0.0000 0.0000

0.0183 7.3865 7.3865 -6E-05 0.0178 0.0024 0.0065 0.0000

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Project

System-Zone clear cell: input data

calculation date shaded cell: calculated by macro "newductsize"

shaded cell: user input, cell or column

Duct Size and Rectangular/round duct conversion Run macro "newductsize"

supply air flow = cfm dp100= return segoutdoor air flow = oacfm e =

return air flow = rcfm rho =

subcountmax = 6 supply duct segments return seg

D=(1.3(a*b)^.625)/(a+b)^.25 Curve fit of dia for dp100=.095 (first guess): D=alog(.38

airflow height dia width dp100 branch sbrcount L f

cfm in in in iw/100' cfm ft

1575 14 16.6 16.5 0.090 390 20 0.017931

1185 12 14.9 15.6 0.090 200 15 0.018547

985 12 13.9 13.5 0.090 450 22 0.018965

535 10 11.1 10.2 0.090 150 8 0.020457

385 10 9.8 8.1 0.090 300 12 0.02133985 0 5.6 0.0 0.090 85 20 0.026265

72 0 5.2 0.0 0.090 20 0.026938

324 10 9.2 7.1 0.090 12 0.021827

450 10 10.4 9.0 0.090 8 0.020913

829 12 13.0 11.9 0.090 22 0.01937

997 12 14.0 13.6 0.090 15 0.018938

1325 14 15.6 14.5 0.090 20 0.018301

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ents: 0 means returns correspond to supply segments>0 means returns are entered by user

ents = 0

352*log(cfm) + .00864)

count countf countw fact fact1 diff diffw

30 12 8 7.467784 7.46786 -7.6E-05 0.000835

30 12 9 7.34282 7.342872 -5.2E-05 0.000787

30 11 8 7.261387 7.261467 -8E-05 0.000565

29 10 5 6.991693 6.991619 7.39E-05 0.000826

28 11 8 6.845639 6.845543 9.58E-05 -0.0005822 13 8 6.170421 6.170344 7.66E-05

20 13 8 6.092783 6.092701 8.28E-05

28 12 8 6.768711 6.768652 5.82E-05 -0.00072

29 11 7 6.915003 6.914936 6.62E-05 -0.00069

29 11 4 7.185162 7.18521 -4.8E-05 -0.00067

30 11 8 7.266681 7.266763 -8.2E-05 0.000617

30 12 6 7.391912 7.391974 -6.2E-05 0.000551

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