PAGE 30

TABLES TO AID IN PIPE SELECTION

DISCLAIMER: This information is displayed for general approximation only.  It does not constitute a recommendation for a given application.  Local codes and equipment manufacture's instruction override this "public domain" information

 

CORRECTED PRESSURE DROP (FRICTION) PER 100 FT. DUCT LENGTH

ADJUSTMENT OF DUCT DESIGN PRESSURE FOR EQUIVALENT LENGTH (NORMAL RESIDENTIAL DUCT CALCULATION SETTING - .10) PER 100 FT
(1200 CFM MAX) .08 RETURN

PRESSURE DROP (IN. OF WATER COLUMN)

TOTAL EFF                                                                                                                                         LENGTH                                                                                                                                            
DUCT & FITTING                                                                                                                                    
IN FEET            .05    .06    .08    .10    .125   .14    .16    .18    .20    .25    .30    .34    .375    .40     .50    .625     .75    1.00
35-44              .13    .15    .20    .25    .32    .35    .40    .45    .50    .63    .75    .85    .95    1.00    1.25    1.50    1.90    2.54
45-54              .10    .12    .16    .20    .25    .28    .32    .36    .40    .50    .60    .68    .76     .80    1.00    1.26    1.52    2.02
57-64              .08    .10    .13    .17    .21    .23    .27    .30    .33    .42    .50    .57    .63     .67     .83    1.05    1.26    1.68
65-74              .07    .09    .11    .14    .18    .20    .23    .26    .29    .36    .43    .49    .54     .57     .72     .90    1.08    1.44
75-84              .06    .08    .10    .13    .16    .18    .20    .23    .25    .31    .38    .43    .47     .50     .63     .79     .94    1.26
85-94              .06    .07    .09    .11    .14    .16    .18    .20    .22    .28    .33    .38    .42     .45     .56     .70     .84    1.12
95-104             .05    .06    .08    .10    .13    .14    .16    .18    .20    .25    .30    .33    .38     .40     .50     .63     .75    1.01
105-114            .05    .05    .07    .09    .11    .13    .15    .16    .18    .23    .28    .31    .34     .37     .47     .57     .69     .91
115-129            .04    .05    .07    .08    .10    .12    .13    .15    .17    .21    .25    .28    .31     .33     .46     .51     .62     .82
130-149            .04    .04    .06    .07    .09    .10    .11    .13    .14    .18    .21    .24    .27     .29     .36     .45     .54     .72
150-169            .03    .04    .05    .06    .08    .09    .10    .11    .13    .16    .19    .21    .24     .25     .31     .39     .47     .63
170-189            .03    .03    .04    .06    .07    .08    .09    .10    .11    .14    .17    .19    .21     .22     .28     .35     .42     .56
190-214            .03    .03    .04    .05    .06    .07    .08    .09    .10    .13    .15    .17    .19     .20     .25     .31     .37     .50
215-239            .02    .03    .04    .05    .05    .06    .07    .08    .09    .11    .13    .15    .17     .18     .22     .28     .33     .44
240-264            .02    .02    .03    .04    .05    .06    .06    .07    .08    .10    .12    .14    .15     .16     .20     .25     .30     .40
265-289            .02    .02    .03    .04    .04    .05    .06    .07    .07    .09    .11    .12    .14     .15     .18     .23     .27     .36
290-324            .02    .02    .03    .03    .04    .05    .05    .06    .07    .08    .10    .11    .12     .13     .17     .20     .24     .33
325-374            .02    .02    .02    .03    .04    .04    .05    .05    .06    .07    .09    .10    .11     .11     .14     .18     .21     .29
375-424            .01    .02    .02    .03    .03    .04    .04    .05    .05    .06    .08    .09    .09     .10     .13     .16     .19     .25
425-474            .01    .01    .02    .03    .03    .03    .04    .04    .05    .06    .07    .08    .08     .09     .11     .14     .17     .22
475-524            .01    .01    .02    .02    .03    .03    .03    .04    .04    .05    .06    .07    .08     .08     .10     .13     .15     .20
525-574            .01    .01    .02    .02    .02    .03    .03    .03    .04    .05    .06    .07    .07     .07     .09     .11     .14     .18
575-625            .01    .01    .01    .02    .02    .02    .03    .03    .03    .04    .05    .06    .06     .07     .08     .10     .13     .17

 

MAXIMUM DUCT VELOCITY (FEET PER MINUITE)


      MAIN DUCT*           BRANCH                                      
SUPPLY    RETURN      SUPPLY     RETURN         APPLICATION             
1000........800........500........500.......APARTMENTS, RESIDENTS       
1300.......1100.......1000........800.......AUDITORIUMS, THEATERS       
1500.......1300.......1200.......1000.......HOSPITAL ROOMS, HOTEL ROOMS 
2000.......1500.......1600.......1200.......BANKS, LIBRARIES, OFFICES,  
                                            MEETING ROOMS, RESTAURANTS, 
                                            RETAIL STORES               
3000.......1000.......2200.......1500.......INDUSTRIAL                   

*Use branch duct velocities where sound control is critical.

CFM=  BTUH                                       
    1.08xT.D.       (TEMPERATURE DIFFERENCE - DRY BULB)

 

 
DUCT SIZE/CAPACITY (100 EQUIVALENT FEET)
SUPPY OR RETURN SIZES


 CFM     ROUND      RECTANGULAR                                       
  50.......5".........8 X 6
  75.......5".........8 X 6
 100.......5".........8 X 6........3 1/4 X 10......................(110)
 125.......6".........8 X 6........3 1/4 X 12......................(140)
 150.......7".........8 X 6........3 1/4 X 14.........(160) (STUD SPACE)
 175.......7".........8 X  6
 200.......7".........8 X 6
 250.......8".........6 X 10.........8 X 8......................6 X 12
 300.......9".........6 X 10.........8 X 8......................6 X 12
 350.......9".........6 X 10.........8 X 8......................6 X 12
 400.......9".........6 X 10.........8 X 8......................6 X 12
 500......10"........10 X 10........12 X 8......................8 X 12
 600......12"........10 X 10........12 X 8......................8 X 12
 700......12"........12 X 10........14 X 8.....................10 X 12
 800......12"........12 X 10........16 X 8.....................10 X 12
 900......14"........14 X 10........18 X 8.....................12 X 12
1000......14"........14 X 10........18 X 8.....................12 X 12
1200......14"........16 X 10........22 X 8.....................14 X 12
1400......16"........18 X 10........24 X 8.....................16 X 12
1600......16"........20 X 10........28 X 8.....................18 X 12
1800......16"........24 X 10........30 X 8.....................20 X 12
2000......18"........26 X 10........32 X 8.....................20 X 12
2500......18"........30 X 10........20 X 14....................24 X 12
3000......20"........36 X 10........24 X 14....................28 X 12
3500......22"........40 X 10........28 X 14....................32 X 12
4000......24"........26 X 16........32 X 14....................38 X 12        

                      8" JOIST - 375 CFM; 10" JOIST - 525 CFM (RETURN)
The above charts when used in conjunction with a "duct calculator" can be a big aid to designing proper air distribution systems.  All capacities are based on total effective feet of 100 (duct and all fittings in the run).  The common, residential design perimeter for friction loss is .10 drop per 100 feet on the supply side and .08 on the return side.  Each fitting is assigned a drop in pressure value due to friction by means of its relationship to straight pipe (effective feet). See Page 31.

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