Document 06g542dBbNVLq1oV84vyoOOLV

470 CHAPTER 20 1955 Guide in a rectangular duct should be at least one-half the duct dimension in the plane of the turn.' Warm air ducts passing through cold spaces or located in exposed walls, should have 1 to 2 in. of insulation. Special attention should be given to the-problem of noise elimination. The metal duct connection to and from the furnace casing and fan housing should be broken by strips of fire resistant fabric. Motors and mountings must be carefully selected for, quiet operation. Electrical conduit and .water piping must not be fastened to; nor make contact with; the fan housing. Installation of a fan directly under a return air grille is usually avoided. STANDARD COMBINATIONS OF PARTS The combinations of parts selected as standard by the National Warm Air Heating and Air Conditioning Association are shown in Tables 1 and Fig. 3. Recommended Type of Floob ob Low Sidewall Installation on Out side Wall* * Registers set to direct air upward along the wall at as wide an angle as possible. 2. A method for selecting these combinations is indicated in the following section Simplified Method of Design. SIMPLIFIED METHOD OF DESIGN A simplified method for selecting the combinations of branches, boots, stacks, and registers, is given3 in Manual 7 of the National Warm Avr Heating and Air Conditioning Association. In this method, the sizes of the branch ducts are obtained from two tables giving their Btu capacities. The proper combination of parts for each branch can be determined if the follow ing information is available. . Location of room, that is, whether on first or second story. . Actual horizontal length of duct from bonnet to boot, in feet. . c. Btu loss from room to be heated. ~ :: : : . :' . d. Equivalent lengths in feet of''all fittings and of the register. Fig. 4 shows the values of equivalent-lengths of fittings commonly used for domestic systems. Forced Warm Air Systems 471 Table 1. Capacity and Sizing Table--First Story For Warm-Air and Return. Air Stack{Branch', and Registers Equiv. Length op Fittings and Registers Horizontal Length Furnace to Register, .,. Ducts* I nsulated Attic Ducts ' First Story'............... Room Heat Loss-^btuh t. Col. a ; Col. b Col. c Col. d Col. e Col. f Col. g Col. h Col. i Col. j Up to 70 Eq. Ft. 71 to 100 Eq. Ft. 101 to 130 Eq. Ft. 131 to 165 Eq. Ft. 166 to 200 Eq. Ft. Up to 7. 8-12 13-17 18-25 Up' to 5 6-9 10-13 14-18 7,200 6,700 >,8s100 5,600 . . 26-35 ', 36-45 >. . .40-55 Up to 7 8-12 -.13-17 . 18-25 ; 18-25 3 .26-35 36-45 , 46-55 Up to 5 6-9 . 10-13 14-18 4,800 .4,100 3,500 3,000 5;500 5,100 ^ 4.800 4,500 . 26-35 36-45 ...- 46-55 -Up to 7 8-12 .13-17 v.,18-25 19-25 26-35 36-45 46-55 ;Up to 5 6-9 10-13 . .14-18 3,900 3.400 3,000 : 2,600 4,600 .4,300 . :4,100 .3,800 ,26-35 .36-45 .48-55 Up to 7 . 8-12 13-17 , 18-25 19-25 26-35 .36-45 ,46-55 -.Up to 5 . 6-9 v 10-13 -.14-18 3,300 3,000 2,700 2,300 4,100 3,800 3,600 3,400 26-35 . . 36-45 46-55 Up to 7 8-12 13-17 18-25 - .19-25 : 26-35 36-45 46-55 Up to 5 -0-9 .10-13 14-18 .2,900 * 2,600 2,300 2,000 s: 3,800 3.500 3,300 3,100 26-35 36-45 46-55 19-25 . 26-35 36-45 46-55 2,700 2,400 ; 2,100 1,700 .12,500 11,700 10,800 9,900 V 8,500 >7;400 5,400 5,500 9,900 9,200 8,600 8i 100 7,100 6,200 . 5,400 4,600 8.500 7,900 7,400 : 6,900 6,100 5.300 4,700 4,000 -7,300 6,900 6,400 r6,000 5,300 4,700 4,200 3,600 6,500 6,100 5,700 .5,400 4; 800 4,300 3,800 .. 3,000 . 16,000 15,000 14,000 13,000 11,000 9,900 8,700 7,700 13,100 . 12,300 11,600 10,900 9,700 8,500 7,500 6,500 11,300 10,600 . 10,000 9,400 .8,400 7,400 6,500 5,400 9,800 9,100 8,600 8;100 7;200 6,400 : 5,600 4,700 8;800 8,200 7,700 7,200 <6,400 * 5,700 5.000 3;900 19,100 18,000 17,000 16,000 25.000 23,400 21,600 19,800 14,200 17,000 12,500 14,800 11,000 . 12,800 9,600 : : 11,000 16,300 15,400 14;500 13,700 19,800 18,400 17,200 16,200 12,200 10,800 9,500 .8/300 14,300 13,500 12,700 11,900. 14,200 12,400 10,800 9,200 17,000 15,800 14,800 13,800 10,500 9,300 8,300 . . 7,000 . 12,300 s 11,700 11,000 10,300 . 12,200 10,600 9,400 8,000 14,600 13,800 12,800 12,000 9,100 8,100 7,100 6,000 11,000 10,500 9,900 9,300 10,600 9.600 8.400 7,200 13,000 12,200 11,400 10.800 . 8,300 7,300 . ;,*6,400 . 5,100 ; . 9,600 8,600 7,600 6,000 32.000 30.000 28.000 26,000 22,600 16,800 17.400 .15,400 . 26,200 24.600 23.200 21,800 19.400 17.000 15.000 13.000 22.600 21.200 20.000 18,800 16,800 14.800 13,000 10.800 19.600 18,200 17.200 16.200 14.400 12,800 11,200 9,400 17.600 16.400 15.400 14.400 12,800 11.400 . 10,000 80,000 75.000 70.000 65.000 56.500 49.500 43.500 38.500 65.500 61.500 58.000 54.500 48.500 42.500 37.500 33.500 56.200 52,600 50.200 47;300 42.000 37.000 32,400 27.000 49.200 45.800 41,900 : 40; 300 31.800 28,100 23.500 44,100 51.500 38.800 36,000 32,000 28.200 24,700 19,500 Combination Number Btacksb No. Size Rectangular Branch Size Round Branch Size (Diam) Number of Joist Spaces and minimum Depth-Return Air registers: Low Wall, High Wall or Baseboard 41 1 10x3H 3x8 5 1 at 3 10x6 Popsters: Floor-Warm Air 8x10 .42 1 10x3H 4x8 6 1 at 3 . 10x6 8x10 Registers: Floor-Return Air trunk Duct Increase, Inches 6x10 or 4x14 1 6x10 or 4x14 2 43 .1 12x3 M 5x8 7 1 at 4 12x6 9x12 6x)2 or 6x14 3 44 1 14x3H -6x8 8 1 at 5 14x6 9x12 longer 6x14 45 - 2 10x3)4 8x8, -.9 1 at 6 or 2 at 3 (2)10x6 or (1)24x6 10x12 -,46 2 12x3M - 40x8 .10 1 at 7 or 2 at 4 (2)12x6 or (1)30x6 12X14 : 47 15x8 12 1 at 9 or 2 at 5 6x30 6x30 : :. 8x30 45 12 * Uninsulated ducts irr heated'spaces and insulated ducts in unheated spaces. ^. ,- : Note: For returiV air a 14x3^i in. stud space may be used instead of 10x3)4 in. stack. Where 12x3)4 in. or.14x3)4 inrstack is required,-a 14x3Hin. stud space may be-used only when inside of.stud space is smooth without protruding plaster keys. The number of joist spaces for combination 47 is based on 2X8 in. joists. ue space may be used with 2x10 in. joists. The limiting factor for a duct combination is the stack capacity.