Document RadBnk5Yxyn63Dq9voBaMD94X

American Society of Heating and Ventilating Engineers Guide, 1930 the main is equivalent to a 22.2-in. diameter round pipe. From Fig. 3, 30 per cent of this is a pipe 13.5 in. in diameter, and referring again to Table 3, the rectangular equivalent branch is a 12 x 13-in., 10 x 15-in. or any other desirable combination. Exhaust Systems In the design of piping for an exhaust system where-no dampers are provided, it is considered good practice to make the area of the main pipe approximately 20 per cent greater than the sum of the areas of the branch pipes at that point. This. method gives greater uniformity of distribution than where the increase in area is not made. INSTALLATION OF AIR DUCTS The following suggestions will be found helpful in the installation of air ducts: 1. For heating and ventilating work, ducts 6x6 in. represent a minimum size. In any place where other considerations do not outweigh, round pipe for small flues is recommended. 2. Abrupt turns or sharp bends should never be made. Elbows should have a throat radius equal to the depth of the duct. 3. Transformations and offsets should not be made abruptly. Angles greater than 45 deg. should be avoided. In any case, care should be taken not to restrict the true cross-sectional area. 4. Tees or branches from main ducts should make curved connections. Accessible and operative volume dampers should be used. Adjustable dampers should be provided with a means of indicating from the outside, the true position of the damper. 5. Access doors to ducts should be hinged and tightly fastened. Fire dampers in S supply and vent ducts should be Ms in. steel plate, held by a fusible link for release at ' 160 deg. fahr. 6. Air intake should be screened with 1 in. mesh or less, at least No. 10 wire galvanized. 7. Final exit for exhaust discharges should be protected from the weather and pointed away from prevailing wind where possible. 8. Underground ducts should be water-proofed, provided with means of access for inspection and cleaning; also a drain connection trapped to sewer. 9. The use of varied metals and special finishes for different conditions encountered is of prime importance. The present day metal market affords wide range of choice, and a study of requirements for the individual application should be made. 10. Wherever water is present or condensation is likely to occur, galvanized iron sheets should be used. 11. When service encountered is severe and the material used may be subjected to rapid deterioration, either from abrasion or excessive corrosion, heavier gages of materials than ordinarily used are recommended. 12. In exposed work the same method of formation should be used throughout. All visible work should present a neat and workmanlike appearance. 13. The following table gives recommended gages of galvanized iron or steel sheets used for ducts, both rectangular and round: Round Ducts Diamcter, In. 6 in. to 19 in. 20 in. to 29 in. 30 in. to 39 in. 40 in. to 49 in. 50 in. and above Gage U. S. Standard No. 26 gage No. 24 gage No. 22 gage No. 20 gage No. 18 gage Rectangular Ducts Width, In. 4 in. to 18 in. 19 in. to 30 in. 31 in.' to 60 in. 61 in. to 118 in. 120 in. and above . 452 T a b l e 3. C ir c u la r E q u iv a l e n t s of R e c t a n g u la r D ucts for E q u a l F r ic t io n 20, Chapter 27--Air Ducts 22 23 24 w oo -- <o z to O OO r iq ap to SO i-- 04 04 to to to to Ot to ro 04 --4 tO 04 tO tO ^ to to to to t0 04> tO * 4-4to to to to rotO ctootcooto aP 0400 ^ Os Os t0o4 04 00 CO 4OsOOOsO 04 C4O40 tO to -4 00 -4 04 tO tO to to to to SP>ap --00 ^so ttoo*to sto ^Or>4< r-oooo to to to to o4oO OOnn spsp^^1 04 04 tO 04 t0o4 04 tO 04 -4 t-000 C4 04 04 to OO to SO O -4 04 tO to to to to 4-- s 04 ttoo to* ttoo *t*0> SO 04 CO ap -a 04 OO to4t--o 4to-CtOO tOtO^*^1 >OON t0O4 a0p4 04 SO .*1-4 sssa 00*0 04 -4 04 to to to to CO too 04 to ap SO to to to to tO ap --a p- 04 00 ttooto to rto- tao.otoeOtoto ---- 04 to ap so 04 04 04 04 009 0 10 S0O4 S0O4 40--4 0004 tO 00 ^ 00-4 04 to tO tO -- OC* -- 04 04 to aP to to to to 4-tO"* atop ttoo ttoo to --0.044(t--o 4t--o 0to0 0to0 to to *o ^ to 0400- to 04 O- 04 to -a 00'*<ds -- -- CM 04 0044 t0o4 ^04 o 0(0 s 04 04 04 04 0040 04 04 otO -a -a 04 to to to to tO ttoo atop apo StoO to to <--o 4to- OO ap O--' N Os Os 00 00 **C>4 O -- 04 to 04 04 04 04. ap SO 04 04 04.04 4--^s -4 00 r04- o04o04 04 tO 04 O-a --04 to CO to to ^s* 04 to to ap tO tO t*J to apap ^s SO to *o to to to NNDO 00 Os O to 04 0s04< 04 04 0--4 0044 t0o4 to ap so 04 04 04 04 OO to 04 OO r-- 00 oo 04 04 04 04 to --a t/J to 00-4 04 tO tO CO OO to oo to --a 04 04 tO o to to to oo to oo to tO ap ap to to to to o <ONrN 4-- oo oo *--> to o -- 04 -- 04 04 04 -4 Os SO to tO tO ^s SO 04 04 04 04 t- to <OsOt.N 04 04 04 04 to-as tO CO 04 04 04 to r- 04 t-- 04 -- -- 04 to to to to (-044- 04 04 tO O ap to to to to SO -- SO -- OCNOCO * -- 00^* -4 00 V> -as 04 --a --O SO t-t- co oo -- -- 04 --04 0044 tCO4 *004 ,04 t0O4 t0o4 04 s04 40--4 0004 0004 04 OO-- 04 to to 0 -- 04 04 to tO *0 to to ^ to to O^1 Os r- r- r- *> 04 00 OO OS tO 04 IO -4 04 04 to 04 04 04 04 04 OO 4* <Osq 04 04 04 04 to to 4--4--00 04 04 04 04 oo 004004 04 tO *o to t-- tO OtO t--O --tO room ap ap so CO to O0 C4 <o to to ICOON 4-00 4--^ -- P4 04 04-04 04 04 04 OO * t0o4 t0O4 404* 404* * * t0o4 S0O4 0S4 04 *C0tO*-- -- SO tO 40--4 40--4 00400004 04 040410 04 t-- tot-- to to ^ to so 00 to 04 0.0. oo Os 00 to 44 NO -4 04 --04 0--4 04 CO tOCO 04 04 to to 04 04 04 04 to 00 04 0aP ap SO SO 04 04 04 04 04 O aP (-- 4-- 04 04 04 04 00 04 O 4-- CO 00 04 04 04 04 -a -- 04 Os "O tO 04 0-04 0. -a -a I tO 4-- --a SO to C-- CM 04 to ro ap ap WJ 0 SO 4-00 Os Os -044 0--4 0044 0044 to to ap ap 04 04 041 04 04040404 04040404 0<0 ZZ OV)Ostj> 00 04 to -* *> SO O* -4 00 to tq0N O to -4 so 00 OO -as -as o04o04 --04 --04 O-^s CO 04 0044 0044 0044 t0O4 ap 4-- t0O40*P40aP404* -- SO 04 S04O0S4O0S4O04 oo V OO n; t- MinooN O 04 OO O' ^ssqiOC to to ONOOOO O" OO tO -- -- -- 3 4- -a to O -a -a -a 04 04 04 04 04 0 04 04 04 tO 04 04 04 04 to tO ap aP ap 04 04 04 04 oo ro oo 04 0 9>9iO to so to (N <N rq SO 04 oO O' to ap ap so ap OS <0 tO s so 4-- 0-04 sO O --2--2 00 -a >* --a --a 04 04 CO -- sOaO o04 0--4 0--4 --04 --apt-- 0044 0044 0044 t0O4 OOOO 0\ -- aP 00 -- ^ 4-- 04 00 tO 04 tO tO 00 04 -- to to <o 00 04 * *(- **0 4--4-- CO OOOO 04 04 -- ----04 ^4--004 04 O04 --04 0--4 'OOt t-- OO 00 C4 >0 04 O' Os 9s to 00 -- af 0-2 > --` -- --a 04 04 to toosno to to I t t so 4>NO<0 C--4-- 04 ap 4-- 4-- CO 00 4-00410 CO Os to t-- 4--4--00 to 4- OO 00 CO Os to 00 tO Os O iqO^OO -4-- -- 04 SO 04 04 04 04 to o to o (-> ro Tf af OO -a ap I-- aP so to SO -- to SO 00 O to >n 4--4--4-- OS 5 aoS 00 Os O -- 04 ro ap SO <OP>0 <*4ap 04 04 04 04 00 04 ap 04 tO to tO *to 0to0 O" 0ap4 aaPp ap OaOp SOO 04 aP OO O 04 ap so so sO so a 453