Document jg5VR2p3OqnyZKoxkv9rV2kE5

468 CHAPTER 19 1956 Guide *9 Gouge jbvrtfOQta! thkkf extendingjb` beyond Cosing. ^ Incombustible Spacers rotr space-open Insulated with Otr Space, or cov ered with magne 310, osbe&tos, or bond Inner l/ner-from top casing ring to grate level ttetat cosing Tornace foundation- cf brick, cement'or other like ) incombustible material Fig. 3. Details op Furnace Bonnet, Casing, and Foundation (From NWAH & ACA Manual 5, Fifth Edition) Table 5. Resistances of Warm Air Boot Combinations Expressed in Elbow Equivalents Wabm Aib Boot A: B C D E F G H I J K L Name of Combination 45-Deg Angle Boot and 45-Deg Elbow 90-Deg Angle Boot Universal Boot and 90-Deg Elbow End Boot Offset Boot 45-Deg Angle Floor Register--Second Story Offset Offset Hound Side Take-Off Offset Starting Collar Straight Starting Collar Equivalent No. or 90*Djsq Elbowb .i i i 2 2 3 2 1 1 3 Fig. 4. Details of Bonnet and Leader of Gravity Warm-Air Furnace (From NWAH & ACA Manual 5, Fifth Edition) Gravity Wami Air Systems 469 Table 6. Warm Air Carrying Capacity, Btub Delivered, First Story Registers Actual Lenqth (Bonnet to Boot) Feet Combi- nation No. No. or 1 2 31 4 1 2 32 4 1 2 33 4 1 2 34 4 1 2 35 4 6 SH 7 m 2. i st Is 1 2a ' s 4 6 8 10 4 6 8 10 12 14 4 6 8 10 12 14 16 18 4 6 8 10 12 14 16 18 20 22 6,020 5,850 5,680 5,510 5,340 5,170 5,000 4,830 4,660 4,490 7,620 7,400 7,180 6,970 6,760 6,540 6,320 6,110 5,890 5,680 9,400 9,140 8,870 8,600 8,340 8,070 7,810 7,540 7,270 7,010 13,350 12,970 12,590 12,210 11,830 11,450 11,080 10,700 10,320 9,950 5,850 5,660 5,490 5,330 5,160 5,000 4,840 4,670 4,510 4,340 7,360 7,150 6,940 8,730 6,520 6,320 6,110 5,910 5,700 5,500 9,090 8,840 8,580 8,320 8,060 7,800 7,550 7,290 7,040 6,780 12,910 12,540 12,170 11,800 11,430 11,060 10,690 10,320 9,950 9,580 5,620 5,460 5,310 5,150 4,990 4,830 4,670 4,510 4,350 4,190 7,120 6,910 6,710 6,510 6,310 6,110 5,900 5,700 5,500 5,300 8,780 8,530 8,280 8,030 7,780 7,530 7,290 7,040 6,800 6,550 12,450 12,100 11,750 11,400 11,050 10,700 10,350 10,000 9,650 9,300 5,420 5,260 5,110 4,960 4,800 4,650 4.500 4,350 4.190 4,040 6,860 6,660 6,46Q 6,270 6,080 5.890 5,690 5,500 5,300 5,110 8,460 8,220 7,980 7,740 7,500 7,260 7,020 6,780 6,550 6,310 12,010 11,670 11,330 10,990 10,650 10,310 9,970 9,630 9,290 8,950 5,240 5,090 4,940 4,790 4,840 4,500 4,350 4,200 4,050 3,910 6,630 6,440 6,250 6,060 5,880 5,690 5,500 5,320 5,130 4,940 8,180 7,950 7,720 7,490 7,260 7.030 6,800 6,560 6,330 6,100 11,610 11,290 10,950 10,620 10,300 9,970 9,640 9,320 8,990 8,660 Notes: Carrying capacity and length of run increased with basement depth. Length of trunk and carrying capacity of gravity extended plenum installations should be based on the 6 ft basement depth capacities. pressed in equivalent elbows are shown in Table 5. It is essential that free areas be maintained throughout fittings. Figs. 3 and 4 show recommended practice as given in Manual 5 of the National Warm Air Heating and Air Conditioning Association. ' For con struction, design features, and ratings of gravity furnaces see Chapter 16. Carrying Capacity The Btu per hour carrying capacities of the selected warm air and return air combinations are shown in Tables 6, 7 and 8. The selected types of return air ducts and fittings are shown in Fig. 5. Design Procedure The steps to be taken in designing a gravity warm air duct system are: 1. Calculate the heat loss from each room as explained in Chapters 9,'ll and 12. 2. Prepare a layout showing (a) furnace, (b) chimney connection, (e) warm air registers (whether floor, baseboard or wall), (d) return air grilles. 3. Indicate on each warm air leader (using symbols shown in Fig. 6): (a) whether the room to be heated is on first or second story; (ft) the approximate length of leader pipe in the basement; (c) the number of right angle elbows and equivalent elbows (Table 5) required, including the elbow at the boot connection (see Fig. 2); (d) whether the register is to be located in the floor, in the baseboard, or in the wall.