HEATING SYSTEMS The principal systems of heating dwelling houses are the use of steam, hot water or hot air, generated by furnaces (located usually in a base ment or cellar), and the use of closed coal, oil, or gas stoves, or of open grates, which may be placed in stoves or in fireplaces. Each of these sys tems has its advantages and disad vantages, but, disregarding the first cost, it is probable that, from the double standpoint of efficiency and economy, they may all be rated about as follows: First, steam; second, hot water; third, hot air; fourth, the open grate; fifth, the closed coal stove; sixth, closed oil stove; seventh, closed gas stove.
Furnaces.— Furnaces vary greatly in the amount of coal that they con sume to produce a given temperature. At best only a small percentage of the actual heat value of the fuel is realized, and the future will doubtless witness great improvement in this di rection. At present a number of new devices are on the market, of which one of the most notable is the under feed system. This furnace is so con structed that the fuel is deposited in a chamber below the fire box, where it is gradually warmed before being forced from below by means of a lever into the fire box. Thus the heat is saved which is wasted in other types of furnaces by raising the tempera ture of cold fuel thrown directly upon the blaze, and less fuel is consumed to produce a given increase of tem perature. There is also less unneces sary combustion. The difference may be illustrated by the burning of two candles, one right side up and the other upside down. The former con sumes no more fuel than is necessary; the latter produces an inevitable waste.
Another device consists in a perfo rated plate of metal, placed across the fire box so that the flame is broken up into a large number of small jets of burning gas. The plate also be comes exceedingly hot and thus assists the combustion of the gases.
Other important devices are means to prevent heat from being wasted by radiation in the cellar or basement or by escaping up the chimney. The in direct-draught furnace contains a de vice which causes the heated products of combustion to circulate in such a way, before going up the chimney, as to heat every part of the furnace.
The saving in the use of these devices would far exceed the difference in the first cost, even if they were much more expensive than other types of heating apparatus, which is not neces sarily the case. Hence, their univer sal use is to be recommended.
Steam and Hot-water Heating Sys tems.—The first cost of installing a steam or hot-water system is consid erable, and both require a good deal of care to produce satisfactory results. They also demand some provision for ventilation, which is an additional ex pense. Both steam heat and hot wa ter are difficult to adjust to sudden changes of temperature. In mild weather, steam heat is not economical, because the furnace must be kept hot enough to boil water in order to pro duce any steam at all, and hot-water heat is inconvenient, since, if the weather becomes suddenly mild when the pipes are filled with hot water, the house will be too warm. On the other hand, if the water is allowed to cool and the temperature again changes, considerable time is required in either system to reheat the boiler.
Thermostat.—The most satisfactory results with the steam and hot-water systems are obtained by the installa tion of the thermostat, an instrument which can be adjusted at any given temperature, so that if the heat falls below this standard the furnace draught will be automatically opened; if it rises above, the furnace draught will be closed. Thus a uniform tem perature can be maintained with the least possible attention.
The Ideal System. — Probably the ideal system of heating is the so-called vacuum steam system, by which a par tial vacuum is formed in the steam pipes. Thus, steam may be produced in the pipes at a temperature below 212°. An attachment, known as the automatic vacuum valve, which pro duces a similar effect, can be supplied to ordinary steam radiators. Prob ably, then, an underfeed, indirect draught furnace with a system of ventilation and a suitable thermostat, while somewhat expensive to install, would give the most perfect and sat isfactory results.