Document YDXzawDMZJJ5GE1D1J1qzEqz0

CHAPTER 19. GRAVITY WARM AIR FURNACE SYSTEMS perature of the warm air entering the room at the register. For most successful operation, the furnace should be centrally located with respect to register and stack positions so that the leaders will be of uniform length and as short as possible, in which case the frictional resistance to air flow and the temperature loss from the ducts will be about the same for all runs. CHAPTER 19 arm `Ju.rnace jSy.&tem6 Warm Air Leaders, Stacks, and Registers; Return Air Ducts, Grilles, and Shoe Connections; Outline of Design Procedure; Furnace Capacity WARM air heating systems of the gravity type are described in this chapter1, and those of the mechanical type are described in Chapter 20. In the gravity type, the.motive head producing flow depends upon the difference in weight between the heated air leaving the top of the casing arid the cooled air entering the bottom of the casing, while in the mechanical type a fan may supply all or part of the motive head. Booster fans are often used in conjunction with gravity-designed systems to increase air circulation. In general, a warm-air furnace heating plant consists of a fuel-burning furnace or heater, enclosed in a casing of sheet metal or brick, which is placed in the basement of the building. The heated air, taken from the top or sides near the top of the furnace casing, is distributed to the various rooms of the building through-sheet metal warm-air pipes. The warm-air pipes in the basement are known as leaders, and the vertical warm-air pipes which are run in the inside partitions of the building are called stacks. The heated air is finally discharged into the rooms through registers which are set in register boxes placed either in the floor or in the side wall, usually at or near the baseboard. A sectional view of a typical plant showing good installation practice is given in Fig. 1. The air supply to the furnace is usually taken entirely from inside the building through one or more recirculating ducts, although in some cases an outside air supply duct is provided. WARM AIR LEADERS, STACKS, AND REGISTERS In a gravity circulating warm-air furnace system, the size of the leader pipe to a given room depends upon the length of the leader and the tem- lThe engineering data which follow are from University of Illinois. Engineering Experiment Station Bulletins Nos. 141. 188. 189 and 246; Warm Air Furnaces and Heating Systems, by A. C. Willard. A. P. Kratz, V. S. Day. and S. Konzo. See also Standard Code Application Manual for Gravity Warm-Air Heating Systems, published by the National Warm Air Hotting and Air Conditioning Association. 358 Fig. 1. A Sectional View of a Typical Plant Showing Good Installation Practice3 N. Sleeve with air space - around leader. where AB.. THooupsoefcchhimimnneeyy, naot bleeansdts2nfoereot fafsbeotsv.e ridge of passing through wall. O. Dampers in all leaders. roof. C. Flue lining, fireclay. D. All joints air tight, EF.. ANtoleoathste8r,cino.nbnreiccktio. n beside that to furnace. GH.. CSmleoakneouptipfera, emnedaflnudshdwooitrh, ianinrteigrhsut.rface of flue. P. Transition fittings. . Q. Rectangular wall-stack. RS.. DBaissterbibouartde rpeipgeissteerq. ually aroundbonnet. T. -Floor register. V. Return air face. V. Panning under joist. I. Draft door. JL.. UCsaesifnlugehothoidmobrleb.onnet, top of all leader collars W. Transition collar. X. Round return pipe. YZ.. TTompnosiftsiohnoeshaotec.asing not above grate level. on same level. KM.. CRaosuinndg bleoaddye.r,. pitch 1 in. per foot.- ' .(Froffl N.W.A.H.&A.C. Assn! Stands* Cods Action / In the Standard Code for Installation of Gravity Warm Air Heating Systems, the design was originally based on the heat carrying capacities per square inch of leader pipe area, as shown in Table 1. These values were based on register air temperatures of 175 F. In a recent revision of the entire design procedure, as outlined in the section entitled Outline of 359