Figure 7 (fi/. 9) exhibits a form of an American base-burning coal stove, with section removed to show the interior arrangement of the maga zine, or supply-hopper, and fire-g-rate. A popular form of heating apparatus is the Franklin stove (fig. 8), which combines the sanitary advantages of the open fireplace or g-rate with the economical heating effect of the closed stove, or hot-air furnace. A modification of the Franklin stove has the open-grate fire with provision for warm-air circulation. It may be used, therefore, for heating several apartments by a suitable arrangement of hot air flues. A convenient adjunct to either a stove or a hot-air furnace is that shown in Figure 6. This consists of an extension of the smoke-flue to the floor, at which point it is perforated with suitable openings to admit air. The pipe leading from the stove is provided with a damper; as is also the extension-pipe. By closing the door of the stove or furnace and partly shutting off the damper in the stove-pipe and openino, the damper in the 6 auxiliary flue, the draft will be so controlled as to maintain the fire in moderate activity for a long time. A reversal of these operations quickens the fire. By this improvement the heating apparatus can be perfectly regulated without opening the fire-door.
The forms of heating apparatus in which the heat is generated outside the room are extensively used at the present time for public buildings as well as for private dwellings. According to the means employed, these methods are known as " hot-air," " water," or " steam heating." Hot-air Heating is accomplished by air warmed in a special chamber by a stove or heater and conducted by flues to the room where it is needed. The cool air of the room may be taken back to the heating chamber through downward flues, or channels of circulation, to be warmed again, or through -ascending flues, or channels of ventilation, upward to the open air. In the latter case, fresh air from outside must be supplied to the heating chamber. The heater and flues may be arranged in a variety of ways. Fig ures 15 and 16 (pl. ro) represent the hot-air heating apparatus constructed on correct principles by the above-mentioned Engineer Kelling. The lower parts of the cuts show the 'heating chamber (A), in both cross- and longi tudinal-section, and the heater, which consists mainly of cast-iron tubes (B). The former is divided by partitions into sections, according to the number of the rooms to be heated and the amount of heat likely to be lost in them. For cold air, each section has an opening (f) below, which com municates with the main duct (c); and for the heated air above, a corre sponding- opening, which communicates with the hot-air flue. The fire is self-feeding. In Figure 16, / is the receiver for fuel; K, the fire-grate, in steps, with horizontal grate beneath; i, raker for removing ashes; m, turn plate in the smoke-pipe leading to the chimney; and gg, caps for cleaning openings in heating flues. To assure moisture to the air, an evaporator,
seen at c (fig. i5), is set parallel to the heating flues and adjusted from the outside. The manner in which the heating is done is seen in the upper part of the Figure, where a is the register; d, damper for summer ventila tion; and e, damper for spring and autumn. The double damper (b), when the other dampers are rightly adjusted, effects circulation when lifted and ventilation when lowered. The following- directions, prepared for the use of this heater, will complete the explanation: r. For kindling the fire: a open; b lifted; c, f, closed. 2. For winter ventilation: a open; b low ered; c, ri, closed; f open. 3. For ventilation in spring and autumn: a closed; b lifted; c open; a' closed; f open. 4. For summer ventilation: a closed; b lifted; c, f, closed; d open; windows open.
Hot-air Heating in arc United Statcs.—A large proportion of the dwell ings located in cities and populous towns in the United States are heated bv air warmed in furnaces, usually located in cellars, and nuinerous devices are used in connection with such systems. Physicians and sanitary engi neers as a rule regard them as deleterious to health, and especially to those who are closely confined and when the ventilating apparatus is defective.
Furnaces of considerable size and heating capacity are commonly brick cased—an arrangement which greatly facilitates the proper setting of the furnace, and which is desirable on the score of economy, as the masonry aids substantially in preventing the wasteful conduction of heat. Figure 9 Go/. 9) illustrates an improved brick-set furnace with a section cut awav to show the construction, and Figure to exhibits one of the more common forms of furnaces nsnally called " portable heaters." A belief that there are more agreeable and wholesome modes of heating dwellings is leading to changes in prevailing practice, some of which are in the direc tion of a return to open grates, and others toward the use of systems of heating by hot water or by steam.
Hot-water Heating depends upon the circulation of bot water through pipes, the heat being communicated to the air of the room by the walls of the pipes. The chilled air, being specifically heavier, canses the ascent of the warm water, which is specifically lighter. This is accomplished by two methods—one known as " high pressure," the other " low pres sure." In the low-pressure (p/. io, Ac. 17), the water is raised to the boiling-point. In the high-pressure system (fig. r9)—also known as Per kins' method, from the name of the inventor—the water is raised above the boiling-point, and for this reason the system of pipes must be entirely closed.