Document EdYmpVDJ7wYXmvjRq5OMB8Y6N

426 CHAPTER 19 1950 Guide Register and Grille Openings Supply registers located in the floor require attention to keep them clean and are usually avoided. Tests- conducted in the Warm Air Research Residence at the University of Illinois have indicated that comparable results are obtainable with either high side wall or baseboard registers, if proper registers and air velocities are selected. Baseboard registers should be of a deflecting-diffuser type which throw the air downward toward the floor and diffuse it at the same time. For baseboard registers air tempera tures under 125 F, and air velocities over 500 fpm should be avoided as they may cause drafts. High side wall registers must be of such type that the air is delivered horizontally or in a Sightly downward direction, and must be so located as to avoid impingement of air on ceiling or wall. Directional flow diffusing Fig. 1. Recommended Type of BaseBoard AND LOW SlDEWALL REGISTERS* Fig. 2. Recommended Type of High Sidewall Registers1' * Vertical ban with adjustable deflection, or fixed vertical bare with deflections to right and left not exceeding about 23 deg. For low sidewall location, the deflection for horizontal, multiple valve registers should not exceed 22 deg. For baseboard locations, the deflection for horizontal, multiple valve registers should not exceed about 10 deg. b Horizontal valves, in back or front, to give downward deflections not to exceed from 15 to 22 deg. . type registers should be used to.insure best results. Register air velocities should be such that the air velocity will be about 50 fpm three quarters of the distance from the register to the opposite -wall. Velocities through registers may be reduced by the use of registers larger than the connecting ducts. Diffusers should be used to spread the air uniformly over the register face: Basic rules for'the location and selection of registers are given in Section B of Manual 7 of the National Warm Air Heating and Air Conditioning Association. Registers should be well proportioned and decorated to harmonize with the trim. Air supply registers should be equipped with dampers and all registers should be sealed against leakage around edges. The register types shown in Figs. 1 and 2 have been recommended as standard by the National Warm Air Heating and Air Conditioning Association. ; .Return air grilles may be located in hallways, near entrance doors, under windows, in exposed comers,- or inside walls, depending on "location of supply registers. Baseboard returns are preferable to floor grilles. Mechanical Warm Air Systems 427 Table L Warm Air Duct System Combinations of Parts Selected as Standard Combina tion No. 1 41 42 43 44 Stack Size In. Branch Pipe Size, In. Round RecTANOULAB 3 10x31 10x31 12x31 14 x31 <4 6 ; 4x8 6 4x8 7 5x8 8 6x8 Rboxethb Size, In. (Su FlOS. I AMD 2) Babm-boabd High ob Low Sidewall 5 10x6 10x6 12x6 14 x 6 Floos Reoibtebs* 6 8 x 10* 8x10* 9 x 12* 9 x 12* or longer 45 10x3} 9 8x8 (2) 10 x 6 10 x 12* (2-Stacks) or (1) 24 x 6 46 12x31 10 10 x 8 (2) 12 x 6 12 x 14* (2-Stacks) or (1) 30 x 6 Required . Incbhase in Tbunk Duct, In. 7 i 2 3 4 5 7 these items only when the building construction or capacity requirements necessitate the use of floor registers. The state Listed for floor registers correspond to the standard sizes for gravity warm air furnace zyztems, except for tneeu es of the floor box collars. The useof standard blind boxesIssuggested, A 13 x 5} in. stack may be used or i Combination 45, and a 14 x 51 in. stack on Combination 46 with floor registers. Dampers Suitable dampers for air direction or volume control are essential to any duct system. Special care must be used in the design of any system to avoid turbulence and to minimize resistance. Sharp elbows, angles, and offsets should be avoided. Three types of dampers are commonly used. Volume dampers are used to completely cut off or reduce the flow through pipes. Splitter dampers are used where a branch is taken off from a main trunk. Squeeze dampers are used for adjusting the volume of air flow and resistance through a given duct. It is essential that a damper with positive locking-device be provided for each main or duct branch. Labels placed on ducts should indicate the room being served. Damper positions should be marked for summer and winter operation, and to avoid tampering. Ducts The ducts may be either round or rectangular in cross section. The radii of elbows should preferably be not less than one and one-half times the pipe diameter for round pipes, or the equivalent round pipe size in the case of rectangular ducts. Warm air ducts passing through cold spaces, or where located in exposed walls, should have to 2 in. of insulation. Special attention should be given to the problem of noise elimination. The metal duct connection to and from the furnace casing and fan housing should be broken by strips of canvas. Motors and mountings must be carefully selected for quiet operation. Electrical conduit and water piping must not be fastened to, nor make contact with fan housing. Installation of a fan directly under a cold air grille is usually avoided.