Ductwork System Calculation Input Data Sheet

System/Zone Name: XYZ system Project: UVW-123456

Designed by: Designer Date: 10/20/2009

To run this program, fill in the input below, then go to sheet 1 and run the macro "friction factor". A further
explanation of how this spreadsheet works is given on sheet 1. For guidance in selecting values for the
input, consult the ASHRAE Handbook, Fundamentals, "Duct Design". This is Chapter 21 in the 2009
Handbook, but the chapter may be different in other editions. Data generated by sheets 1 and 2 will
automatically be entered in the "Report" sheet.
Roughness e = 0.0003 [-]
Air Density rho = 0.0763 [lbm/ft3] Specific Volume = 13.106
dp/100= 0.09 [inwc/100-ft] (Target pressure drop per 100')
Kinevisc = 0.000163
Supply Air (SA) = 1,575 [CFM]
Outdoor Air (OA) = 250 [CFM]

No. SA Segments = 6
No. RA Segments = 6 Instruction:
Total Duct Segments = 12 1) Input blue cells in Input Tab,
3) Run Macro 1: "fraction factor" in
fixture library Sheet 1 Tab,
fixture type, C, and dp input by user 4) Print out Report in Report tab.
code Fixtures Fixture C dp [inwc]
1 fan out 0.72
2 el 0.11
3 tee thru 0.04
4 tee branch 0.8 AHU
5 fan in 0.3 OA SA
6 diffuser 0.04
7 ret grille 0.03 RA

Duct Segment Input - For round ducts, input duct height as zero (0)
Duct Seg. Air Flow Duct Height Duct Length fixture C or dp
No. cfm in ft code a code b code c code d
1 1,575 14.0 20.0 1 2 3
2 1,185 12.0 15.0 3
3 985 12.0 22.0 3 2
4 535 10.0 8.0 4 2
5 385 10.0 12.0 3
6 85 0.0 20.0 4 6
7 72 0.0 20.0 7 3 2
8 324 10.0 12.0 3
9 450 10.0 8.0 4
10 829 12.0 22.0 3 2
11 997 12.0 15.0 3
12 1,325 14.0 20.0 5 3 2
13
14
15
16
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 Duct System Pressure Drop Calculation Result

System - Zone XYZ system

Project Number UVW-123456
Designer Designer
Date 10/20/2009

System/Zone Name: XYZ system Designed by: Designer Date: 10/20/2009

duct airflow height width dia velocity Re l'nth duct dp dp/100' vel. dp fix'tr dp tot. dp
leg Q H W D V Re L dP_duct dp/100' dP_v dP-fx dP_tot
No. [cfm] [in] [in] [in] [fpm] [-] [ft] [in. w.g.] [iw/100'] [in. w.g.] [in. w.g.] [in. w.g.]
1 1,575 14 17 17 1,018 146,745 20.0 0.017 0.084 0.07 0.06 0.07
2 1,185 12 16 15 952 123,097 15.0 0.013 0.085 0.06 0.00 0.02
3 985 12 14 14 901 109,185 22.0 0.018 0.083 0.05 0.01 0.03
4 535 10 10 11 821 76,809 8.0 0.008 0.096 0.04 0.04 0.05
5 385 10 8 10 741 61,894 12.0 0.011 0.091 0.03 0.00 0.01
6 85 0 0.01 6 433 22,234 20.0 0.013 0.063 0.01 0.05 0.06
7 72 0 0.01 6 367 18,833 20.0 0.009 0.047 0.01 0.03 0.04
8 324 10 7 9 716 55,818 12.0 0.011 0.093 0.03 0.00 0.01
9 450 10 9 10 768 68,124 8.0 0.007 0.090 0.04 0.03 0.04
10 829 12 12 13 883 99,182 22.0 0.019 0.088 0.05 0.01 0.03
11 997 12 14 14 912 110,515 15.0 0.013 0.085 0.05 0.00 0.01
12 1,325 14 15 16 968 131,290 20.0 0.017 0.083 0.06 0.03 0.04

0.155 0.26 0.41

DUCT SIZE CALCULATION SPREADSHEET Run macro "friction factor"
Project UVW-123456 system-zone XYZ system fixture library
<-- input data from Input tab fixture type, C, and dp input by user
formulas: code Fixtures Fixture C dp [inwc]
Reynolds Number Re = 8.56*D*V fixed parameters (user input) 1 fan out 0.72 0
D=(1.3(a*b)^.625)/(a+b)^.25 Roughness e = 0.0003 [-] 2 el 0.11 0
V=Q/((Pi*D^2/4)/144) Air Density rho = 0.0763 [lbm/ft3] 3 tee thru 0.04 0
Target dp/100' = 0.090 [inwc/100-ft] 4 tee branch 0.8 0
Colbrook 1/f^.5 = -2*log(12*e/3.7/D+2.51/Re/f^.5) kinevisc = 0.000163 5 fan in 0.3 0
dp = (12*f*L*rho*(V/1097)^2)/D Zone air flow = 1575 [CFM] 6 diffuser 0 0.04
Zone outdoor air = 250 [CFM] 7 ret grille 0 0.03
Fixture Loss vdp = rho*(V/1097)^2 specific volume = 13.106
fixdp = vdp*C or fixdp = dp from fixture library

After the input sheet is completed, the size of each duct segment that will give the exact desired pressure loss per 100 feet of duct length. If a height is imput, the exact
width corresponding to the height and hydraulic diameter is also given. There is no need for the user to reference sheet two except to verify results. For convenience, the
branch flow rates are also shown on sheet 2.

In the real world, there are no decimal fractions in duct diameters or the width of rectanglular ducts. Also, the objective is to calculate the external static pressure for a fan
or air handler. Therefore, the user must run the macro "friction factor" on sheet 1. This macro rounds the diameter of round ducts, or the width of rectanglular ducts to the
nearest inch. If the duct is rectangular, the macro recalculates the hydraulic diamter to correspond to the new width. Velocity (V) and pressure loss per 100' (dp/100') is
then recalculated for the new hydraulic or integer duct diameter (dia D). Duct friction loss for each segment is calculated and totaled (duct dp). Fixture loss (fixdp), based
on loss coefficients or pressure losses from ASHRAE data and manufacturer's performance data, is calculated based on the fixtures input from the sheet Input. Finally,
the external static pressure (systotdp) is calculated and totaled.

All data below calculated by macro except fixture codes, which are input by the user
branch count max = 12 This macro will clear the contents of all calculated cells. The fixture loss input cells, N32 - Q100 will not be cleared
duct leg airflow Q height a width b dia D V Re L duct dp dp/100' vdp fixdp systotdp fixture C or dp
cfm in in in fpm ft iw iw/100' iw iw iw coda codb codc codd
1 1575 14 17.0 16.8 1018 146745 20 0.017 0.084 0.066 0.057 0.074 1 2 3 0
2 1185 12 16.0 15.1 952 123097 15 0.013 0.085 0.057 0.002 0.015 3 0 0 0
3 985 12 14.0 14.2 901 109185 22 0.018 0.083 0.051 0.008 0.026 3 2 0 0
4 535 10 10.0 10.9 821 76809 8 0.008 0.096 0.043 0.039 0.047 4 2 0 0
5 385 10 8.0 9.8 741 61894 12 0.011 0.091 0.035 0.001 0.012 3 0 0 0
6 85 0 0.0 6.0 433 22234 20 0.013 0.063 0.012 0.050 0.062 4 6 0 0
7 72 0 0.0 6.0 367 18833 20 0.009 0.047 0.009 0.031 0.041 7 3 2 0
8 324 10 7.0 9.1 716 55818 12 0.011 0.093 0.032 0.001 0.012 3 0 0 0
9 450 10 9.0 10.4 768 68124 8 0.007 0.090 0.037 0.030 0.037 4 0 0 0
10 829 12 12.0 13.1 883 99182 22 0.019 0.088 0.049 0.007 0.027 3 2 0 0
11 997 12 14.0 14.2 912 110515 15 0.013 0.085 0.053 0.002 0.015 3 0 0 0
12 1325 14 15.0 15.8 968 131290 20 0.017 0.083 0.059 0.027 0.043 5 3 2 0
0 0 0
0.155 0.256 0.411 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
Project
System-Zone green cell: input data from Input sheet
calculation date shaded cell: calculated by UDF or formula

Duct Size and Rectangular/round duct conversion

supply air flow = 1575.0 cfm dp100 = 0.090 return segments:

outdoor air flow = 250.0 oacfm e = 0.0003
return air flow = 1325.0 rcfm rho = 0.0763 spvol= 13.106
kinevisc = 0.000163
subcountmax = 6 supply duct segments return segments =
D=(1.3(a*b)^.625)/(a+b)^.25 Curve fit of dia for dp100=.095 (first guess): D=alog(.38352*log(cfm) + .00864
airflow height dia width dp100 branch sbrcount L
cfm in in in iw/100' cfm ft
1,575.0 14.0 #VALUE! #VALUE! #VALUE! 1.0 20.0
1,185.0 12.0 #VALUE! #VALUE! #VALUE! 390.0 2.0 15.0
985.0 12.0 #VALUE! #VALUE! #VALUE! 200.0 3.0 22.0
535.0 10.0 #VALUE! #VALUE! #VALUE! 450.0 4.0 8.0
385.0 10.0 #VALUE! #VALUE! #VALUE! 150.0 5.0 12.0
85.0 0.0 #VALUE! 0.0 #VALUE! 300.0 6.0 20.0
72.0 0.0 #VALUE! 0.0 #VALUE! 0.0 7.0 20.0
324.0 10.0 #VALUE! #VALUE! #VALUE! 0.0 8.0 12.0
450.0 10.0 #VALUE! #VALUE! #VALUE! 0.0 9.0 8.0
829.0 12.0 #VALUE! #VALUE! #VALUE! 0.0 10.0 22.0
997.0 12.0 #VALUE! #VALUE! #VALUE! 0.0 11.0 15.0
1,325.0 14.0 #VALUE! #VALUE! #VALUE! 0.0 12.0 20.0
0.0 0.0 0.0 13.0
0.0 0.0 0.0 14.0
0.0 0.0 0.0 15.0 0.0
0.0 0.0 0.0 16.0 0.0
0.0 0.0 0.0 17.0 0.0
0.0 0.0 0.0 18.0 0.0
0.0 0.0 0.0 19.0 0.0
0.0 0.0 0.0 20.0 0.0
0.0 0.0 0.0 21.0 0.0
0.0 0.0 0.0 22.0 0.0
0.0 0.0 0.0 23.0 0.0
0.0 0.0 0.0 24.0 0.0
0.0 0.0 0.0 25.0 0.0
0.0 0.0 0.0 26.0 0.0
0.0 0.0 0.0 27.0 0.0
0.0 0.0 0.0 28.0 0.0
0.0 0.0 0.0 29.0 0.0
0.0 0.0 0.0 30.0 0.0
0.0 0.0 0.0 31.0 0.0
0.0 0.0 0.0 32.0 0.0
return segments: 0 means returns correspond to supply segments
> 0 means returns are entered by user

return segments = 6
D=alog(.38352*log(cfm) + .00864)

module 1 friction factor macro

module 111 fcalc UDF
module 12 AirCap UDF
module 21 Air Dia UDF
module 31 Wcalc UDF
module 51 AirPd UDF