HEATING AND VENTILATION. 69.". HEATING AND VENTILATION. or other liquids the resistance coils or the cases which contain them may be placed in the liquid to bo licated. Elei-lric healing is used but slightly, except in electric street-railway ears, where current is more readily available than any other means of heating. The heaters are placed beneath the seats, running throughout the length of the car: thus a good distribution of the heat is possible, making a pleasant contrast with the heat derived from the small red-hot coal-stove formerly used. In special cases, where economy is of rela- tively small importance in comparison with, .say, advertising effects or convenience, electric heat- ing is used for apartments in buildings. In a few- restaurants and clubs it is also used for cooking. Its cost is so much greater than the more direct utilization of fuel that the general use of elec- tric heating is a luxury in which even the very rich do not indulge. This may be the better appreciated when it is remembered that there is a loss at every step in the process of developing heat by electricity, and that the steps are many. Thus, there is a loss in the combustion of fuel." in the transformation of the heat so ob- tained into steam, in the utilization of steam in the engine, in the conversioii of the power thus obtained to electric energy, in the transmission of that energy through wires to the electric heater, and finally in the reconversion of the elec- tric energj' to heat. One of the great advantages of the electric current for cooking is that though there is great loss of power in the course of transmission, there is little loss of heat at the point where it is applied, while only a small proportion of the fuel burned in ordinary cook-stoves is utilized for cooking. See Electric Heater. Heating with Artificial G.s is far less ex- j)ensive than electric heating, but with illuminat- ing gas at $1 per 1000 feet it costs some four to ten times as much as heating with coal. Where cheap fuel gas is available the case for artificial gas heating is not so bad. Gas may be used in fireplaces, stoves, hot-air furnaces, and steam and hot-water systems. For occasional use in fireplaces or other lieating apparatus placed in living-rooms gas is often advantageous. It makes no dust, and thus possesses a great advantage over coal or wood. But without gootl ventilation it vitiates the atmosphere: or at least it consumes much of the available oxygen and may give off objectionable ga.ses. Gas for cooking is rapidly growing in favor, particularly for siuiimer use. The Choice axd Desicx of Heatixg Plants. The factors entering into Ijoth the choice and design of heating plants are many and various, including range of temperature through which the air is to be raised, the size and character of the building to be heated, the sort of fuel to be used, the heating system to be employed, and the amount of ventilation, if any, to be provided. As to temiierature, the usual basis for all American calculations is the attainment of 70° Fahr.. the original temperature varying with the locality and season, sometimes falling to — 20° Fahr.. or even lower. In the matter of the indi- vidual buildings there must be considered the area of the ground plan, the number of stories, the number and cubical contents of the several rooms, the areas of ex|)osed or outer wall and window surfaces, and the material of which the outer walls are built, wliethcr of wood, brick, or stone. A large ground plan, for instance, pre- cludes heating with hot air, unless a fan or blower is used, or many furnaces are employed. The character and area, of the outer walls of the buildings have an important bearing upon the amount of heat lost by jjassage through them. The choice of fuel depends largely upon local prices, but there are other important considera- tions, such as the smoke nuisance from soft coal, which may be (but often is not) avoided with large ])lan"ts, but cannot be avoided in most plants for heating private residences. In the design of a s])ecilic heating plant the relation of grate to healing surface of the liot-air furnace, steam boiler, or hot-water heater must first be con- sidered, having in mind the fuel and the type of furnace or boiler to be employed. Next comes the relation of the heating surface to the radiat- ing surface, when steam or hot water is used, and finally the proportion of the radiating sur- face to the cubical space to be warmed. Any skimping on the various proportions named means either insufficient warmth in very cold weather, or overworking the heating apparatus, a practice which is wasteful of fuel, may injure the heating plant, and, worst of all, be a menace to health. The foregoing factors in the choice or design of heating apparatus are by no means the only ones, but are suflicient to show the tech- nical nature of many of the problems involved, and the desirability of intrusting the solution of the latter to persons of skill and experience. In fact, the possible savings in fuel and doctor's bills are so great, to say nothing of matters of comfort and convenience, that a thoroughly com- petent engineer or architect may w'ell be consult- ed in the selection, or design, and installation of heating plants for all buildings, from moderate- sized residences up. For all but very small heat- ing plants, and for all systems of ventilation, this will be essential to the securing of the best possible result. Central Heating Plants are employed to lieat a number of buildings from a common source. Steam or hot water is conveyed from the central station to the several buildings through underground pipes. Within the buildings the heat is distributed in the same manner as when generated on the premises. Hot water n.ust be re- turned to the central station, but the condensed steam is drawn out of the system in each building and discharged into the sewer. By first passing the exhaust through an economizer indirect heat- ing and ventilation may be afforded. The central station equipment consists of boilers for steam and heaters for hot water, or else utilizes the ex- haust steam from electric light and power sta- tions, as explained below. The large size and greater efficiency of the central station, as com- pared with isolated plants for private heating, results in economy in constraction and operation, in addition to which there are the savings due to the use of cheaper fuel and automatic devices for feeding the coal to and removing the ashes from the furnaces. The consumer reduces his fire risk, avoids the dirt and dust incident to isolated heat- ing, the bother of getting coal into and ashes out of his cellar, and all possible vitiation of the air of his house by furnace gases. The coi^- munity at large may be benefited by a tnarked reduction in both the ashes and the smoke nui- sance, the latter being of crreat possible impor- tance where soft coal is used for domestic fuel. ]'"iiiallv, the consimier mav be assured of an
