Hot-air furnace

“ A hot water furnace disturbs the natural conditions of the air the least, and, on that account, is a very healthy means of artificially heating air. But they are necessarily expensive, and so few persons really appreciate the value of pure air, that but few will go to the expense of introducing them. It is a mistake to suppose that they do not dry the air, so to speak. You cannot elevate the temperature without increasing the capacity for moisture. A hot water furnace, therefore, requires the artificial evaporation of water to give the warmed air its true hygrometric condition. ”

“ Furnaces where air is heated in the furnace-chamber by coils of steam or by hot water, though costing more at first, require much less fuel, and do not involve the evils of warming by hot iron.
The safest and pleasantest way of warming a dwelling is by steam-coils, provided there are fire-places or hot-air flues to carry off bad air. Without these, this is the most unhealthful mode of all, as there is no fresh air brought in, and what is heated is breathed over and over, till it is poisonous. ”

“ Where direct heat is not desired, a register opening in the ceiling of a downstairs room will sometimes carry enough heat to the upper chamber to make it comfortable for sleeping purposes.
Since furnace efficiency is largely dependent upon air control, a strong wind sometimes makes it difficult to heat portions of the house. To meet this emergency there is a combination hot-air and hot-water heater which supplies radiators on the upper floors, or elsewhere if desired. The additional cost is practically all in the installation, as the same fire furnishes both forms of heat. ”

“ Hot gas and hot air burn rapidly and completely, and if properly proportioned yield exceedingly high temperatures. Seeing that in this process a part of the heat of combustion yielded by the fuel is generated in a subsidiary appliance and is thus lost to the furnace, it appears at first sight somewhat surprising that this system of firing is very considerably more efficient than the old “direct” system where the whole of the fuel is burnt in the furnace itself. ”

“ I do not know that cast-iron furnaces are more liable to be overheated than others, and you cannot "burn the air" with them if they are, unless you burn the furnace too. You may fill a room with air, every mouthful of which has been passed between red-hot iron plates, not over half an inch apart, and I do not suppose the essential properties of the air will be perceptibly changed, or hurt for breathing when properly cooled. ”

“ First, it is like the old-fashioned stove in that an even heat is hard to maintain. Second, with coal or wood as the usual fuel, there is a discouraging amount of dust generated. Third, the doors to all rooms must be left open so that the currents of hot air can circulate. One chooses between frosty seclusion and balmy gregariousness. Yet, in spite of these very definite "outs," it is far better than no furnace at all. It is, in fact, an excellent stop gap for the country house owner who is not prepared to invest in the more expensive heating plants at the moment. ”

“ It is known, that two-thirds of the fuel have been saved in the gas-works by this distribution of the furnace. For the purpose of heating apartments, the great object is to supply a vast body of genial air; and, therefore, merely such a moderate fire should be kept up in A, as will suffice to warm all the pipes pretty equably to the temperature of 220° Fahr.; and, indeed, as they are laid with a slight slope, are open to the air at their under ends, and terminate at the upper in a common main pipe or tunnel, they can hardly be rendered very hot by any intemperance of firing. ”

“ However, a furnace properly attended will not need firing during church service. Remember, a large volume of warm air is what you want, and not a small volume of hot air. Never cover the grating or close the cold-air duct to cool off while there is fire in the furnace, but open the doors or windows of the church and check the fire. The closing of the grating or cold-air duct will injure the castings of the furnace by overheating them. ”

“ The following may aid in this duty:
When a furnace does not draw well, it often is owing to the stoppage by fine ashes or soot, and then the smoke-flues must be cleaned. The fewer and more simple the smoke-flues the less this trouble will occur. Sometimes the shaking of a furnace makes cracks in joints, and this causes outflow of gas and also diminishes the draught.
When iron is very hot, it burns the particles floating in the air, making an unpleasant smell and dryness. A large furnace, therefore, is better than a small one that must be kept very hot. ”

“ The want of care in regulating the dampers of the airbox often makes a house cold, however great the furnace181 fire. A strong wind requires the dampers nearly closed, especially when it is on the side where the air enters from without. Every furnace should be supplied, not by cellar air, but by air taken through a shaft from a height, and so more pure.
Remember that an open fire, or an opening into a hot-air flue, will ventilate properly in all seasons and all weathers. ”

“ A short time should be allowed so as to be assured that the center of the tool is as hot as the outside. Then quickly remove the tool from this preheating furnace to the full heat furnace. Keep the tool in this furnace only as long as is necessary for the tool to attain the full temperature of this furnace. Then quickly remove and quench in oil or in a dry air blast. ”

“ For the deficiency of heat, or the failure of some of the hot-air pipes of hot-air furnaces in certain winds and weathers in large houses or specially exposed rooms, the best addendum is an open fire-grate. With this provision in northerly rooms, to be used occasionally, hot-air furnaces may be made to produce all the advantages of steam heat in even the largest dwelling-houses. ”

“ The sun was chiefly depended upon for heat, for there were no proper stoves, though braziers were used to burn coals upon, the smoke escaping through the aperture in the ceiling, and, in rare cases, hot-air furnaces were constructed below, the heat being conveyed to the upper rooms through pipes. ”

“ In houses heated by furnaces or other modern systems, lack of a damper in the fireplace flue may interfere with uniform heating, particularly in very cold windy weather, whether or not there is a fire on the hearth. When air heated by the furnace is carried up the chimney there is a waste of the furnace fuel, but a damper partially open serves a slow fire of hardwood without smoking the room or wasting heated air from the main heating system. ”

“ It was gravel that moved underfoot with never-failing treachery, gravel made hot by the rays of the sun, and flinging up a scorching heat while it crawled and blistered underfoot. On midsummer days men had perished here, driven mad by the dancing of the air and the dread of the movement where they trod. ”

“ The hot air of a furnace is a sirocco; the heat of a wood-fire is only intense sunshine, like that bottled in Lacrimae Christi. Besides this, the eye is delighted, the sense of smell is regaled by the fragrant decomposition, and the ear is pleased with the hissing, crackling, and singing,—a liberation of so many out-door noises. Some people like the sound of bubbling in a boiling pot, or the fizzing of a frying-spider. But there is nothing gross in the animated crackling of sticks of wood blazing on the earth, not even if chestnuts are roasting in the ashes. ”

“ The success of warm-air heating depends on a natural circulation of air thruout all the rooms which are to be heated. The air is the vehicle of transmission of the heat from the fire to the rooms to be warmed.
A warm-air furnace is simply a large stove encased in a sheet-metal jacket (Figs. 26 and 27) . The jacket is usually insulated with asbestos, since the stove is set in the basement where radiation of heat is not desired. The air entering the casing is warmed by the stove. As the air is warmed, it expands and becomes lighter, so rises to the top of the furnace ”

“ In these furnaces, the regenerator chambers themselves are generally placed underneath the melting furnace, and they are built of fire-brick and filled with loosely-stacked fire-bricks, whose function it is to absorb or deliver the heat. In the most modern type of furnaces of this class, the gas-regenerators are omitted entirely, the air only being pre-heated by means of regenerators, while the gas enters the furnace direct from the producer, thus carrying with it the heat generated in the producer during the gasification of the fuel. ”

“ Hot water and steam heat cost more for installation, but have many advantages over the furnace. Their chief drawbacks are the space usurped by radiators, lack of ventilation, and the possibility of an occasional breakdown. ”

“ This increase in furnace volume in the direction of the flame insures free expansion and a thorough mixture of the oil with the air, and the consequent complete combustion of the gases before they come into contact with the tube heating surfaces. In such a furnace flat flame burners should be used, preferably of the Peabody type, in which the flame spreads outward toward the sides in the form of a fan. There is no tendency of the flames to impinge directly on the heating surfaces, and the furnace can handle any quantity of flame without danger of tube difficulties. ”

“ The present system of each man keeping up separate fires all over his house is as crude, and extravagant, and unnecessary as it would be for every man to make his own gas or have his own well for water.
Where a steam furnace is used, two-thirds of the heating surface should be put below the floor and fresh air brought into it, and from there conducted to the rooms through large pipes. This warmed air should be let into the room at the floor, and an opening into an exhaust flue, two-thirds the size of the inlet, should be provided at the floor for the escape of the foul air. ”

“ The gas on leaving the producer passes along fire-brick flues or passages to the furnace proper; the path which it is now caused to take varies somewhat according to the arrangement of the furnace in question. Modern gas-fired furnaces usually belong to one of two distinct types according to the manner in which the heat of the escaping products of combustion is utilised for heating the incoming gas and air ”

“ It can be applied in a working pit, and is certain and steady in its operation. The only defect of the furnace is, its liability to explosion when the current of air by which it is supplied, becomes so charged with inflammable air, in its passage through the workings, as to be explosive. This objection to the furnace is, however, greatly obviated by what I call the system of double ventilation. The principle of this system is to supply the furnace with a current of air, which is not exposed to the hazard of being contaminated by an admixture of inflammable air. ”

“ Furnace Design—Too much stress cannot be laid on the importance of furnace design for the use of this class of fuel. Provided a good type of burner is adopted the furnace arrangement and the method of introducing air for combustion into the furnace are the all important factors. No matter what the type of burner, satisfactory results cannot be secured in a furnace not suited to the fuel. ”

“ The burning of this modern furnace takes place under a forced draught of air blast from eight to twenty pounds per square inch. This pressure serves to drive the air upward through the hundred-foot mass which burns within the furnace. Otherwise, the fire would smother. The gas which results from the imperfect combustion within the furnace is a most valuable by-product and serves a valuable purpose in promoting the furnace operation, and sometimes leaves a product to sell. A part of the gas is taken to the boilers, where it generates power for the blowing engines. ”