Document v13o0LJ4Zn4yOxxByKRd0M2Xw

446 CHAPTER 19 Fig. 3. Equivalent Length of Fittings GROUP 1. WARM AIR AND RETURN AIR BONNET OR PLENUM. 1951 Guide; V Forced Warm Air Systems Fig. 3. Equivalent. Length or Fittings (Continued) CROUP 4. BOOT FITTINGS. - FROM BRANCH TO STACK. 447 GROUP 2, ANGLES AND ELBOWS FOR TRUNK DUCTS, inside radius wioth OF DUCT. A\ - 4 TO 11-10* 12 TO 2 I - 15 22 TO 27-20' 28 TO 33 - 25' 34 TO 42 - 30' 43 TO SI- 40' 52 TO 84-50' T TO 0 12 TO 15 - 55' 16 TO 21 - 75' 22 TO 27 -100* 26 TO 33-125* 34 TO 42-130' 4 TO II 13* 12 TO 21 - 20' 22 TO 27-- 25* 26 TO 42 - 40' bonnet pressure is not high enough to accommodate the pressure loss through the registers, use a higher bonnet pressure. If the register pres sure is critically large, it may be necessary to reduce it by either using two registers in place of one, or using smaller deflection angles, b. Obtain actual duct loss by subtracting register pressure loss from maxi mum bonnet pressure. GROUP 5. STACK ANGLES, ELBOWS. AND COMBINATIONS GROUP 6. RETURN AIR ID* WIDTH - 15* 12* - 15* 10* WIDTH 40* 10*10. Ift'ca. rt cart IO X J 75' 12 X 3 E-85* 14 X 3 b - 90 RETURN AIR UNCR TO .DUCT.. STUD SPACE TO LINER. STUD SPACE TO LINER. R.A. CRRX AND FlTTtNO. R. A. GRILL TO STUO SPACE. R.A. GRILL ONLT. FLOOR GRILL TO LINER c. Obtain the pressure drop, in each duct per 100 ft by use of Table 10. d. Determine duct size by means of air friction chart (such as Fig. 1, Chapter 31), volume (cfm), and pressure drop per 100 ft of duct. B. Return air branches. a. Select a low value of actual duct loss obtained from step b under item A for the suction loss of return duct system.