Document ypjaLZr3rO9nEB3BRgkoQ5qyd

j02_.________________ . CHAPTER 22 ,, 1946 Guide Table 1. . Warm Ajr Duct System Combinations of Parts Selected as Standard ' Combi nation No. Stack Size In. Branch Pipe Size. In. Register Size. In. (See Figs. 1 and 2) Round Rec tangular Baseboard, or Low Sidewall High Sidewall For throws For throws less than more than 13 ft 13 ft 5-i 2 3 4 6 .7 Id41 10x3 6 4x8 10 x 6 10x6 10 x 4 Floor Regis- " TBRS*. Required Increase in Width of Trunk Duct. In. 8 8 x ltt 9. 1 42 10x3K 6 743 12 x 3K 4x8 5x8 10 x 6 12 x 6 10x6 12 x 6 10 X 4 12 x 4 8 x 103 9 x 12a 2 3 44 14 x 3K 8 %45 10x3 (2-Stacks) 9 6x8 14 x 6 14 x 6 14 x 4 .9 x 12a or longer 8x8. (2) 10 x 6 (2) 10x6 (2)10x4 or or or (1)24x6 (1)24x6 (1)24x4 10 X 12a 4 6 46 12x3^ (2-Stacks) 10 10 x 8 (2) 12 x 6 or (1)30x6 (2) 12 x 6 or (1)30x6 (2) 12 x 4 or (1)30x4 12 x 14a 7 Use these items only when the building construction or capacity requirements necessitate the use of floor registers. The sizes listed for floor registers correspond to the standard sizes for gravity warm-air systems, except for the sizes of the floor box collars. The use of standard blind boxes is suggested. SIMPLIFIED METHOD OF DESIGNING DOMESTIC FORCED-AIR SYSTEMS A simplified method for selecting, the combinations of branches, bdots, stacks, and registers, is given in the Code and Manual (Textbook, section No., 7) of the National Warm Air Heating and Air Conditioning Associa tion. 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 following information is available. a. Location of room, that is, whether on first or second story. b. Actual length of basement 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. 3 shows the values of equivalent lengths of fittings ^commonly, used for domestic systems. This simplified method is applicable to structures having heat losses not in excess of approximately 150,000 Btu per hour. The capacities shown in Tables 3 and 4 are based upon the most reliable, data'pertaining to friction losses and temperature drops in ducts. They are also-based upon a 100 deg temperature rise of the air, and a static pressure available for overcoming friction losses in the external duct system alone of 0:20 in. water gage.' The use of this method assumes that the fan in the fan- furnace assembly will be capable not only .of overcoming the resistance of' the external duct system alone, but also the resistances imposed, by the blower inlet, the filter, and the furnace casing. . .. Mechanical Warm Air Systems ' . . ________________ 403 Table 2. Return-Air Duct. System Combinations of Parts Selected as Standard ' Gombi- No. -1 51 52 53 54 55 56 57 Return-Air Intake Size, In. Base board 2 10 x 6 Floor* 3 6x 10 or 4 x 14 Riser Size. In. Where Stack is. Used in Stud Space Branch Pipe Size, In. Round Rec- TANGULAR When Joist Lining IS USEDb Number of Joist Spaces Lined and Minimum Depth of ' Space Required Required Increase in Width of Trunk, Duct (for ; J In. Depth of duct). In. 4 56 7 8 10 x3Kc 6 4x8 1 space of 3 in. depth 1 10 x 6 6 x 10 or 4 x.14 10 x 3}4C 6 4x8 1 space of 3 in. depth .2 12x6 6 x 12 or 6 x 14 12 x 3Hd 7 5x8 1 space of 4 in. depth 3 14x6 6 x 14 14 x 3YiA 8 6x8 1 space of 5 in. depth *4 24 x 6 or 30x6 6 x 30 Two stacks each 10 x 3%c 9 8x8' i space of 6 in. depth or 2 spaces of 3 in. depth 6. 30 x 6 6 x 30 Two stacks 12 x 3^d 10 10 x 8 1 space of 7 in. depth or 2 spaces of 4 in. depth 7 8 x 30 12 15 x 8 1 space of 9 in., 11 depth or 2 spaces of 5 in. depth Use these items only when building construction, or capacities, requires the use of floor intakes. The sizes listed correspond to standard sizes for gravity installations, except floor box collars. The use' of . standard blind boxes is suggested. bBased on 14 in. space between joists. Use full depth of joist, except when joist depth is less than mini mum depth required, in which case a drop pan must be used. This may occur when two or more return ducts are connected to the same joist space. , *If it is desired to use 14 in. x 3H >n. stud space, it makes no difference whether this space has pro truding keys or not. djf it is desired to^use 14 in. x 3H in. stud space, the plaster base must be smooth, without any pro truding piaster.keys to interfere with the flow of air. The combination numbers shown in the right hand column of Tables 3 and 4 correspond to those given in Tables 1 and 2. - Tables 3 and 4 are also applicable for the selection of the return air branches. A depth of 8 in. has been adopted .as the standard for the trunk ducts. The width of a trunk duct serving two. branches is deter mined by adding to the width of the remote branch the value shown in column 9 of Table 1, or column 8 of Table 2. ` For buildings having a heat loss in excess of 150,000 Btu per hour the design procedure may be that given in the Technical Code, Fourth Edition, of the National Warm Air Heating and Air Conditioning Association. Air ' duct sizes and air distribution may also be calculated in accordance .with . data given in Chapters 40 and 41. COOLING METHODS A slight cooling effect may be obtained under certain conditions by the use of the cooler basement air. A more positive cooling effect may be