Document 93p8kK7rrxVQEazL3vJdoQ697

254 CHAPTER 18 1960 Guide Table 5.... Btuh Capacities and Cfm of Individual Ducts in Perimeter Systems ____________________________________Used in Crawl-Space or Basement Construction (Conduded) Section C For 6-<nch Individual Sound Plp and for Baseboard Diffexen Oidy Bonnet Pressure 0.16 in. Static Bonnet Temperature 170 F 5 10 15 20 25 30 35 40 45 50 55 40 65 70 75 B0 0 Btuh Cfm 1 Btuh Cfm 2 Btuh Cfm 3 Btuh Cfm 4 Btuh Cfm 5 Btuh Cfm 6 Btuh Cfm 8570 8000 7450 6910 6420 5960 5560 5150 4800 4450 4160 109.0 107.2 105.5 103-7 102.0 100.4 98.8 97.5 96.1 94.8 93.5 8700 8100 7550 7000 6520 6060 5630 5250 4860 4530 4220 3930 105.5 104.0 102.3 100.7 99.2 97.6 96.2 95.0 93.6 92.3 91.1 90.0 8890 8270 7700 7160 6660 6200 5750 5350 4980 4620 4300 4000 3700 102.8 101.3 99.8 98.2 96.7 95.3 94.0 92.7 91.5 90.2 89.0 87.8 86.5 8440 7870 7320 6820 6350 5880 5460 5070 4700 4350 4020 3710 3440 98.4 96.8 95.3 93.9 92.5 91.3 90.0 89.0 88.0 86.9 85.8 84.7 83.5 8940 93.4 8580 90.0 8690 95.8 8320 92.2 7960 89.8 8080 94.4 7740 91.0 7380 87.6 7500 93.0 7200 89.8 6850 86.5 6980 91.6 6680 88.5 6350 85.5 6500 90.3 6190 87.3 5880 84.2 6030 89.0 5720 86.2 5440 83.1 5580 87.8 5320 84.8 5040 82.0 5180 86.7 4920 83.8 4660 80.9 4800 85.7 4550 82.8 4320 80.0 4450 84.6 4220 81.7 4000 79.0 4120 83.7 3890 80.8 3670 78.0 3820 82.6 3600 79.9 3400 77.3 3520 81.6 3350 79.0 3150 76.5 3250 80.5 3100 78.0 2930 76.0 t The Equivalent ^agth Values used tod included in calculating thi table are: Diffuser and Boot -- 100 ft; Plenum Take-off -- B) ft; uditicau 14 ft eqiiinlest length of boot nod diSoMr count oae additiooel elbow. All cfm values are bond on standard air. Elba* = Mft. For web This is a preliminary estimate of the cumber of diffusers needed. 4. Measure the length and count the number of elbows in each feeder duct. Determine Btuh capacity of each feeder duct from Table 4. Use Table 4 (Section A) for side-wall and Boor diffusers and Table 4 (Section B) for baseboard diffusers. 5. If the total Btuh capacity of all feeders to each room or area equals or exceeds the heat loss of that room or area, the number of feeders initially chosen is satisfactory. If the heat loss exceeds the Btuh capacity of the feeders, use and locate additional diffusers and feeder ducts. 6. The cfm values in Table 4 are used for designing the return-duct system. Perimeter-Radial System in Crawl Space or Base ment Construction The perimeter concept of warm air heating has been ap plied to crawl-space and basement homes by locating the diffusers in the perimeter location and by warming the area underneath the floor of such structures. Although the con struction of the crawl space and the foundation wall is the responsibility of the architect and the general contractor, it is important that the engineer check the construction to make certain that it will not adversely affect the perform ance of the heating system. Details on crawl-space con struction are shown in Manual 4 of the National Warm Air Heating and Air Conditioning Association* The crawl space or basement should be heated to provide warm floors. A simplified design procedure* for an individual duct sys tem is summarized as follows: 1. Calculate the heat loss of each room or area using the method explained in Chapter 12. Consider the basement or crawl space as a part of the structure and calculate its heat loss. Information in Manual 3s supplements that contained in Chapter 12, particularly with respect to crawl-space heat losses. 2. Determine the required furnace-bonnet capacity from the heat loss of the building. 3. Locate the diffusers on the plan. Allow at least one dif fuser for each exposed wall in each room or area of building, and locate them preferably beneath window areas. For resi dential installations limit each diffuser to a maximum of 7,000 Btuh. 4. Determine the required Btuh delivery of each diffuser. Where more than one diffuser is used, per room; proportion the heat loss equally among all diffusers. 5. Measure length and count number of elbows in each duct. From Table 5, determine the duct size (5 or 6-in. diameter) needed. Section A is for 5-in. duct. Section B is for 6-in. duct using side-wall or floor diffusers, and Section C is for 6-in. duct using baseboard diffusers. Perimeter Extended-Plenum Systems in Crawl- Space or Basement Construction The considerations involved in the design of extendedplenum systems are essentially the same as those of the in dividual pipe system. A simplified design procedure is sum marized as follows: 1. Calculate the heat loss of each room or area using the method explained in Chapter 12. Consider the basement or crawl space as a part of the structure and calculate its heat loss. Information in Manual 3** supplements that contained in Chapter 12, particularly with respect to crawi-epace beat losses. 2. Determine the required furnace-bonnet capacity from the heat loss of the building. 3. Locate the diffusers on the plan. Allow at least one dif fuser for each exposed wall in each room or area of building, and preferably beneath window areas. For residential installa tions limit each diffuser to a maximum of 7,000 Btuh. 4. Determine the required Btuh delivery of each diffuser. Where more than one diffuser is used per room, proportion the heat loss equally among all diffusers. 5. Measure the length of each duct and count number of elbows from the extended plenum to the diffuser. Note whether top or side plenum take-offs are to be used. From Table 6, determine the duct size needed. (Note: Use that section of Table 6, Sections A to F, which applies both to the type of plenum take-off and diffuser to be used.) 6. The cfm values in Table 6 are used with Table 7 for Warm Air Heating Systems 255 Table 6.... Heating Capacities and Cfm of Branch Ducts in ExtendedPlenum Perimeter Systems Section A. Side Take-off to 5-fod> Bound Pipe for $>de-wa9. Floor, and board Diffuxerx Extended-Plenum Pressure O.lt in. Static at 160 F___________ Furnace-Plenum Pressure 0.16 in. Static at 170 F No. of Bbowt 0 Btuh Cfm 1 Btuh Cfm 2 Btuh Cfm 3 Btuh Cfm 4 Btuh Cfm 5 Btuh am 6 Btuh Cfm 5 8960 97.2 8070 88.4 7340 81.1 6810 75.0 6350 70.4 5970 65.2 5660 63.0 10 8X00 93.1 7290 85.2 6650 78.6 6180 73.0 5750 68.8 5400 64.8 5120 61.5 15 7310 89.4 6580 82.2 6020 76.0 5600 71.0 5210 67.0 4900 63.2 4630 60.2 Actual length from xfeded-P(*oam to Offoter--Feoi 20 6550 86.0 5950 79.3 5460 73.9 5070 69.2 4740 65.4 4440 62.0 4190 59.1 25 5900 S3-0 5400 76.9 4950 71.9 4610 67.3 4300 64.0 4040 60.7 3800 58.0 30 5310 81.2 4880 74.6 4500 70.0 4200 65.8 3900 62.5 3670 59.4 3430 56.9 35 4800 77.7 4400 72.5 4070 68.2 3800 64.4 3530 61.1 3330 58.3 3100 55.9 40 4330 75.5 3980 70.7 3680 66.6 3420 63.1 3180 60.0 2990 57.4 2800 55.1 45 3900 73.1 3550 68.9 3300 64.1 3080 61.7 2870 58.8 2770 56.2 2520 54.0 50 3510 71.1 3200 67.1 2980 63.7 2770 60.2 2570 57!7 2410 55.3 2270 53.0 55 3170 69.3 2900 65.7 2680 62.3 2480 69.0 2300 56.7 2160 54.4 2040 52.2 60 2850 67.8 2620 64-2 2410 61.0 2230 58.2 2070 55.9 1930 53.7 1800 51.8 Note: When--y of tbe finrt three rant from tbe extended-plenum exceeds 10 ft end 3 elbows, count ! extra elbows for that run. Tbe Equivalent Lcsflh Values used and included In this table are: Diffuser and Boot * U ft; Each Elbow 11 (t; Side Take-off 30 ft. Tapered Extended-Plenum Starting Collar. Section B. Top Take-off to 5-inch Round Pipe tor Side-waU, Boor, and Baseboard Diffusers Extended-Plenum Pressure O.lt in. Static at 160 P Furnace-Plenum Pressure 0.16 in. Static at 170F Actual Length from Extended-Plenum to Dtffuxer--Pool 5 10 15 20- 25 30 35 40 45 50 55 40 0 Btuh 7070 6400 5800 5260 4800 4350 3940 3550 3190 2870 2580 2310 Cfm 77.8 75.6 73.4 71.4 69.5 68-0 66.4 64.8 63.4 62.0 60.6 59.5 1 Btuh 6570 6970 5400 4890 4430 4010 3640 3290 2950 2650 2380 2140 Cfm 72.6 70-8 68.9 67.2 65.6 64.2 62.8 61.5 60.3 59.0 58.0 57.0 2 Btuh 6180 5610 5080 4590 4160 3770 3410 3080 2770 2480 2210 ' 2000 am 68.4 66.8 65.2 63.7 62.3 61.1 60.0 58.7 57.6 56.4 55.3 54.4 3 Btuh 5800 5250 4750 4310 3900 3540 3200 2890 2600 2340 2100 1870 Cfm 64.4 63.1 61.8 60.5 59.3 58.3 57.1 56.3 55.5 64.7 53.9 53.2 4 Btuh 5490 . 4960 4500 4080 3700 3340 3020 2720 2440 2200 1970 1750 am 61.2. 60.0 58.8 57.8 56.7 55.8 54.9 54.1 53.3 52.6 51.9 51.1 5 Btuh 5200 4710 4280 3870 3510 3180 2880 2580 2310 2060 1830 1640 Cfm 58.5 57.5 56.5 55.5 54.5 53.7 52.9 52.1 51.4 50.7 50.0 49.5 6 Btuh 5000 4520 5100 3700 3350 3010 2700 2440 2160 1910 1700 1551 am 56.0 55.0 54.0 53.4 52.4 51.7 51.0 50.5 59.7 49.1 48.6 48.1 -------------- / Note: Where any of tbe first three runs from tbe extended-plenum exceeds 31 ft and I elbows, count 3 extra elbows for that run. Tbe Equivalent length Values used and included in calculating this table are: Diffuser and Boot -- 35 It; Each Elbow -- 13 ft; Top Take-off 60 ft. Tapered Extended-Plenum Starting Collar. sizing the extended-plenum system. No one extended plenum should exoeed 35 ft in length. Design of .Return Duct System for Perimeter In stallations With perimeter systems designed in accordance with the foregoing simplified procedures, there is a circulating head of only 0.05 in. water available on the return side of the system. It is therefore necessary that the return ducts be adequately sized and be as short and straight as practicable. The return grilles may be centrally located, and tbe ducts may be located in the attic or other unheated spaces pro vided they are adequately insulated. Return air may be