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470 CHAPTER 20 Fig. 4. Equivalent Length ojv Fittings . CROUP 1, WARM AIR AND RETURN AIR BONNET OR PLENUM. 1954 Guide"' Forced Warm Air Systems Frc- - ^F^'alent Length of Fittings (Continued) CROUP 4. BOOT FITTINGS. K FROM BRANCH TO .STACK. 471 *>*-- *3ai 70'ta.Pt 45*can VW.A. 35* 40* wrll r.ROUP a. ANGLES; AND. ELBOWS FOR TRUNK DUCTS; INSIDE RADIUS '/% WIDTH OF DUCT. 4^' n re 4 TO IS -- 3 It TO J7 10* 2#.TO 41-13* 42 TO 52-20* 53 TO 64- 25 .'4to ii- io; 12 TO 2 I- 13 22 TO 27 - 20 23TO 33 - 23' 34 TO 42 - 20* 43 TO 31- 4042 TO 64 - 30* ?V' , *> n ^-N- ^n iS 512 TO .3 -33* 20 TO 33 -123* 34 TO 42-130! . ijSaTiOivZSTi-fi* 20 TO 42 - 40* r.nnilP 3. TRUNK DUCT TAKE-OFFS. SB0!,f> 5; STACK ANGLES. ELBOWS, and COMBINATIONS % 5 ax rt ,0`* ^ - 25`ca rr 10'ra ft tO* WIDTH g: : ** ^ -tS* -55* ^ . *rr ' . llbl XX 3sSh * Si! 14 X 3 6 70 o12xX?3 Aft - 47S3. 14 * 3 (l W gROUp fi RETURN AIR .( ture can be expected, in order to secure frequent operation of fans, drafts, and burn ers. The thermostat location should not be on an outside wall, in a bedroom, bath room, or sun room, or in a location where it will be affected by direct radiant beat from cSirnneyr ^r0m a ^reP*ace. or by direct heat from any warm air duct, register or and l^f/pn Svntc*1 control to start blower operations at air temperatures between 110 *, and to stop the blower at about 15 deg below the cut-in point. The lower