Document Bvvn6QB6b79M2yBjLe42r7YVX

886 CHAPTER 49 1946 Guide of the Society of Naval Architects and Marine Engineers; Part I, Vol. -46, 1938, p. 109; Part II, Vol. 49, 1941, p. 208). / Ventilation of Ships,-by J. Dawson (Journal of The Institution of Heating and- Venti lating Engineers, London, Vol. 10, June-July, 1942, No. Ill, p. 89). - Modern Marine Engineers Manual, Vol. II, Sections 16 to 19, Inch (Cornell Maritime Press, 1943). Warship Ventilating, Heating and Air Conditioning, by Comdr. T. H. Urdahl, U.S.N.R., and W. C. Whittlesey (A.S.H.V.E. Transactions, Vol. , 49, 1943, p. 35). Standardized Heating and Ventilating Equipment for Fighting Ships, by Coihdr. T. H. Urdahl, U.S.N.R. and Lt. John Everetts, Jr., U.S.N.R. (Heating, Piping & Air Conditioning, July, 1943, p. 333).-- Designing Warship .Ventilation, with Standardized Equipment,.by Comdr. T. H. Urdahl, U.S.N.R. and W. C. Whittlesey (Heating; Piping & Air Conditioning, August, 1943, p. 419). i- H \' \. * CHAPTER 50 . `lAJater Supply Hot Water Supply Piping, Storage Capacity and Heating Load, Methods of Heating Water, Computing Grate and Coil Surface Areas, Controls, Solar Water Heaters, Friction Loss IN computing the total heating load for a building, it is important to . allow ample boiler capacity for heating the hot water supply^ The amount of warm water used in any large building is variable, depending on the type of structure, usage, occupancy and time of day. .It is neces sary to provide the piping, water heating and storage facilities of suf ficient capacity to meet the peak demand without wasteful excess in equipment cost. The determination of the amount of water used in residences has been well established over a period of time and as a result, reliable factors for water consumption are available. Tests have been made of the amount of water required by standard fixtures in normal use with water at ordinary pressures so that this.information permits a fairly correct basis of design. HOT WATER SUPPLY PIPING As a result of investigations. conducted at the National Bureau of Standards, basic design principles have been- outlined for the design of the hot and cold-water supply piping requirements in a plumbing system1. It is common practice ;to provide circulating piping in all hot water supply systems in which it is desirable to haive hot water available con tinuously at the fixtures. In average sized and small residences arid systems, in which the piping front.the heater .to the fixtures is short, return circulating piping is generally omitted in order to reduce instal lation cost and to reduce heat loss from the piping,'particularly during periods of no water demand. ,, The hot water supply may be distributed by either an up-feed or downfeed piping system. Three common methods of arranging the circulating lines are shown'in 'Fig: T. Although the diagrams apply to multi-story buildings the arrangements (a) and (b) are sometiiries used in residential designs. A check valve should be provided in the run-out frofri each return riser to prevent teiriporary reversal of flow in the piping when a faucet is operi. Proper air venting of a circulating system is extremely important, par ticularly if gravity circulation is employed. In. Fig. 1 (a) arid (6) this is accomplished by connecting the circulating line below the top fixture supply. . With this arrangement, air is eliminated from the system each time the top fixture, is opened. Where an overhead.supply main'is located above the highest fixture as in Fig. 1' (c), an automatic float type air verit is installed at'the'highest point of the systeiri or a fixture branch is.connected to the.top of the main where air venting is desired and then dropped to the-fixture outlet. It is., sometimes, necessary to make an allowance for pressure -drop through the heater when sizing hot water- lines, particularly where in stantaneous hot water heaters are used and.the available pressure is low. 887