Document jmO0BYY1w54601G2j3bJ9VR19

VI American Society of Heating and Ventilating Engineers Guide'TSi^ HMost unit ventilators employ a unique method of air distribution t principal feature is that the air is discharged at a high velocity toward vjL ceiling, with the jet inclined slightly toward the room in order to H-*1l tribute the air over the ceiling. In designing a unit ventilator installat' jj great pains should be taken that nothing will interfere with the opera?011! of this jet. For this reason unit ventilators should never be instalUrl where there is a beam on the ceiling running at right angles to the direct of the air jet. If ceiling beams cannot be avoided, the unit ventilat^l should be placed to discharge parallel to the beams. ^ xExhaustor a R*tum Air DucS TTurred Ctifing 4 Fig. 5. Section Through a Radiator-Heated Room 0$ \G^o I''. J \ Vn- Fig. 6. Section Through a Unit Venh;`1 lator-Equipped Room when,: Heating; Chapter 19--Air Distribution f i inward System - "usually are equipped with downward air distribution with i: ^Miifdiffus_io__n__o_f_the entering_ cool air so as to combine it, both as to orizontai `i*<ifTirC a3-TnIdG dQiHluUtUio_D_nll_,|__wv_vmiituh,i tuhaiev- hiivea*it.evvdi auuir w"h11ich i1n,lev vitably must risev bodies of the patrons. The waste or the recirculated air is with- S--from the room at the floor. If the theater is large, and if the ^ t openings are placed in the side walls at the floor, drafts may be I's^e^aust Hc sit near the openings. There is no objection, how- xcept that of cost, to the use of small exhaust openings under each These may be cleanable floor grilles or may have mushroom covers. ` ,, downward system, if the entering cool air is not deflected hori` iontelly it will fall through the surrounding much hotter air, and will s pJ,,,u`1 Suppty Ducts___ i-w'-y ................................ -............................ Stage j( 1 ' Balcony 1 Warmed 11 , Supply . Stage ' wrrH Downward Ventilation of Ventilation Fig. 7. Section Through a Unit Con ditioner Equipped Room when Cooling Fig. 8. Plan of a . Classroom in a; \School Ventilated by a Central Fan In Fig. 8 the cloakroom ceiling is furred down so as to conceal the metal air supply duct, which is close to the ceiling. The air for ventilation usually is controlled by a duct thermostat near the fan, at a temperature slightly higher than the temperature required in'the room, to allow for heat losses in the duct system. THEATERS Theaters are usually ventilated or cooled by introducing precon ditioned air. No ventilating system for a theater should be given con sideration without definite provision for cooling. Theater cooling generally is far more important than theater heating. There are two widely different methods of theater air distribution, the downward and the upward. 320 reach high velocities by the time it strikes the heads of the occupants. Air at a temperature 10 deg below that of the surrounding air is decidedly ' objectionable when forced over one's.head at a velocity of nearly 400 fpm. Fig. 9 shows a section through a theater with downward ventilation. - The deflectors cause the entering cool air to be spread horizontally so that it will mix with the hotter air. The final escape is through well-distributed i openings in the floor. There have been cases in which the downward system of air distribution such as that illustrated in Fig. 9 gave trouble -due to overheating at the rear, both above and below the balcony, especially when not provided with refrigeration for codling, and when not adequately controlled. It is especially necessary that adequate removal of the heated air be provided at these low-ceiling points and it is probable ..that auxiliary exhaust at or through the ceiling after the manner of the arrangements shown in Fig. 5 would be helpful. Upward System , If no inlet openings are possible in the ceiling, the upward system may be the less objectionable alternative. Fig. 10 shows a section through a theater with the upward system of air distribution. The occupants often suffer from drafts due to the cool air which comes from the unoccupied zones. When the entire seating area is occupied, the upward system 'gives ..little trouble when cooling, and since very little heating is required under such conditions, practically no difficulty is encountered. The maximum 321