District Steam Heating.
At Lockport, New York, a city of about 20,000 population, more than 350 dwellings and business premises are heated by the American District Steam Company, a concern which has installed more than 250 similar plants throughout the Union. The advantages of this system are plain:—cleanliness is promoted; customers handle no coal or ashes, tend no fires or boilers; the heat is more steadily and equably supplied than if it came from individual boilers; heat is ready day or night during the heating season; the hazard from fire is lowered and the risk of boiler explosion is abolished; water may be heated for laundries, bath-rooms and kitchens. Cheap fuel may be used, and stoked by machinery. An individual boiler in a building has to be large enough for its heaviest duty; in many cases it is called upon for but one tenth to one fifth of its full power, with much incidental waste. At a central station only as many boilers of a group are employed at a time as may be worked to their full capacity, responding to the demands of the weather.
At Lockport the steam-pipes are of wrought iron covered with sheet asbestos and enclosed in a round tin-lined wood casing, having a shell 4 inches thick, with a dead air space of about one inch between the tin and the asbestos. In its largest size this pipe has shown a total loss by radiation and conduction of but one part in four hundred in one mile; for the same distance the smallest pipe has suffered a loss of six per cent. Live steam is used at Lockport, but as a rule heating plants are supplied with exhaust steam. When intensely cold weather prevails this may be supplemented by boilers in reserve which supply live steam.
It is worth while to remark the tendency to unify, on lines of the best economy, a service of both heat and electricity. In Atlanta there were recently in operation twenty-two isolated electric plants. The central station installed a steam heating system, and as a result in less than a year all but two of the isolated plants went out of business.