Part 11

The plan of admitting fresh air to a space behind the grates, leading up the air through channels on each side of the fireplace, and ultimately passing it through perforated gratings within the wall or through perforations in the skirting board on each side of the fireplace cannot be commended, as the passages are apt to get choked up with dust, and the temperature of the air cannot be well regulated in its passage into the room. The true object of a fire and chimney flue should not be to supply fresh air, but to extract it after it has done its work.

Fig. 29 illustrates Boyle’s arrangement for cooling the air entering a room in hot weather. It consists of an air-inlet tube of bracket form, made of iron. The part which penetrates the hole in the wall has an outer casing, so that a space of about ½ in. is left between, which is packed with a non-conducting substance, for the purpose of preventing the heat from the wall penetrating into the interior of the opening and acting upon the blocks of ice, which are placed in a movable drawer, and kept in position by means of open galvanised iron or copper-wire netting. The front of the drawer is also double, and packed same as casing. The outer air entering through the grating is deflected by a metal shield on to the suspended blocks of ice, and from thence on to the ice at the bottom of the drawer, and thence up the tube into the room. The air is not only cooled, but purified thoroughly from dust. See also p. 991.

=Warming.=--In connection with warming an apartment, it is obviously a necessary condition that the warmth shall be conserved as much as possible. Hence there is an evil in having too much glass, as it cools the room too fast in the winter season: 1 sq. ft. of window glass will cool 1½ cub. ft. of warm air in the room to the external temperature per second; that is, if the room be warmed to 60° F., and the thermometer stands at 30° F. outside, there will be a loss of 90 cub. ft. of warm air at 60° per second from a window containing a surface of glass of 60 sq. ft. In colder climates than that of England, this subject is of much greater importance. In America, for instance, during the cold weather, there will always be found, no matter how tightly or closely the sashes are fitted and protected with weather-strips, a draught of cold air falling downward. This arises from the contact of the heated air with the cold glass, which renders the air cooler and heavier, and causes it to fall. The air, at the same time, parts with a considerable proportion of its moisture by condensation upon the glass. The cold air thus formed falls to the floor, forming a layer of cold air, which surrounds the feet and legs, while the upper part of the body is enveloped in overheated air. The layers of cold and warm air in an apartment will not mix. The warm air will not descend, and the cold air cannot go upward, except the one is deprived of its heat by radiation, and the other receives its heat by actual contact with a heated surface. This radical difference in the upper and lower strata of atmosphere of the rooms, in which people live during the cold season, is the prolific cause of most of the throat and lung diseases with which they are afflicted. Double windows to the houses, therefore, would not only be a great economy as to fuel, but highly conductive to human longevity.

There are only two ways in which dwelling-houses can be heated, namely, by radiant heat and by hot air. The former is produced by the open fire, and by it alone. The latter is obtained in various ways. The question whether we shall use hot air or radiant heat in our rooms is by no means one to be lightly passed over. Instinct tells us to select radiant heat, and instinct is quite right; it is so because radiant heat operates in a very peculiar way. It is known that as a matter of health it is best to breathe air considerably below the natural temperature of the body--98° F.; in air heated to this temperature most persons would in a short time feel stifled. But it is also known that the body likes, as far as sensation is concerned, to be kept at a temperature as near 98° F. as may be, and that very much higher temperatures can be enjoyed; as, for example, when we sit before a fire, or bask in the sun. Now radiant heat will not warm air as it passes through it, and so, at one and the same time, we can enjoy the warmth of a fire and breathe that cool air which is best suited to the wants of our system. Herein lies the secret of the popularity of the open fireplace. But in order that the open fireplace may succeed, it must be worked within the proper limits of temperature. If air falls much below 40° F. it becomes unpleasant to breathe; and it is also very difficult to keep the body warm enough when at rest by any quantity of clothes. In Russia and Canada the temperature of the air outside the houses often falls far below zero, and in the houses it cannot be much above the freezing-point. Here the open fire fails; it can only warm air by first heating the walls, furniture, and other materials in a room, and these, in turn, heat the air with which they come in contact. But this will not do for North American winters; and accordingly in Canada and the United States the stove or some other expedient for warming air by direct contact with heated metal or earthenware is imperatively required. But this is the misfortune of those who live in cold climates, and when they ask us to follow their example and take to close stoves and steam-pipes, and such like, they strongly remind us of the fable of the fox who had lost his tail. How accurately instinct works in the selection of the two systems is demonstrated by the fact that a succession of mild winters is always followed in the United States by an extended use of open grates; that is to say, the English system becomes, or tends to become fashionable, while, on the other hand, a succession of severe winters in this country brings at once into favour with builders and others a whole host of close stoves and similar devices which would not be looked at under more favourable conditions of the weather. While English winters remain moderately temperate, the open fireplace will enjoy the favour it deserves, as not only the most attractive, but the most scientific apparatus available for warming houses. (_Engineer._)

Heat radiated from a fire passes through the air without increasing its temperature, in the same manner that the sun’s rays in warming the earth pass through and leave the atmosphere at the higher altitudes so bitterly cold that water and even mercury will freeze: it is for this reason that open fires should be lighted some time before the apartment is required for use, so that firstly a glowing fire be obtained (flames do not radiate any material quantity of heat, and practically heat by contact only), and secondly the surrounding objects, walls, &c., be heated by radiation, and these in their turn warm the air.

In discussing the various methods of warming, it will be convenient to classify them under general heads.

To put the reader upon a more familiar basis with this subject, a short explanation of the cause of heat will be here given. Combustion is the chemical union of oxygen (contained in the air) with some other substance for which it has an affinity; as applied to coal, it is the combining of oxygen and carbon producing carbonic acid gas, and it is known to every one that all chemical combinations evolve heat.

Combustion may be said to be complete when coke, wood charcoal, or anthracite coal is burnt, as there is no smoke, the up current is colourless, and these fuels burn quite away, leaving nothing except a little ash, &c., which originally consisted of earthy impurities in the fuel. Ordinary coal contains bitumen (pitch) in its composition, which at a temperature of about 500° to 600° F., distils off as a smoky gas (carbon and hydrogen), but at a higher temperature this is ignited, forming flame by the union of oxygen with the smoke (carbon); the main principles of underfed, smoke-consuming grates are based upon this, with the object of causing all gaseous products from the fuel to pass through the incandescent portion of the fire and so render the consumption of the fuel complete, as will be explained later on.

A good authority says that “the correct method of warming is to obtain everywhere, at will, the warmth most congenial to the constitution with air as pure as blows at the mountain top,” and it might have been added “without an unreasonable consumption of fuel.”

_Open Grate._--The ordinary open grate is too familiar to need any description, but it is wasteful of fuel to a degree that could only be tolerated in a mild climate where fuel was cheap. As a matter of fact, only some 10-12 per cent. of the heat generated in an open grate is utilised, the remainder going up the chimney. But this very fault is in one sense a virtue, in that it performs the ventilation of the apartment in an eminently satisfactory manner. By the addition of a contrivance for regulating the combustion in au open grate, the fuel consumption is much reduced, the combustion is rendered more perfect (diminishing or preventing smoke), the radiated heat is much increased, while the appearance of an open grate is retained, though it is in reality converted into an open stove.

It would not be out of place to explain the cause of draught. After a chimney has been used, the brickwork surrounding and forming it becomes warmed and retains its heat for a very considerable period even if no fire is lighted; this heat is slowly radiated, and warms the air contained in the chimney, rendering it lighter and causing it to rise and flow out at the top; this is immediately replaced by cold air from below, which is warmed and rises as before, and so continues, causing an up current of air to be passing through the flue, its swiftness varying with the heat. The more intense the heat produced by the fire, and the greater the height of the chimney, the more swift is the current of air known as the “draught”; and when once the draught is established it will remain for a very long time without any fire being lighted. A good draught is not to be despised, as can be certified by those who have suffered from the annoyance of a smoky chimney; yet too strong a draught is a disadvantage, as consuming the fuel too rapidly, robbing the fire and apartment of its heat, and causing draughts of another kind, which materially cool the room and tend to cause discomfort; this only applies to the old form of grate, as all or nearly all modern grates have a means of regulating the draught; even the common and old form of grate is provided with a “register” or flap at the back, immediately over the fire (certainly not an economical position for it), through which the smoke passes into the chimney. This flap is provided with the view of having it full open to assist combustion when fire is first ignited, and afterwards partially closing it when fire is established, and so prevent undue loss of heat, but although this “register” is provided with every stove of its kind, _it has not, nor never has had, any means of regulating it_. If the reader has one of these stoves in his residence, as most probably he has, for they are still used in the upper rooms of nearly every building, he can by a simple experiment experience the benefit of regulating this flap. By placing a piece of coal, or stone, or metal, with the tongs, after the fire is established, at the joint or hinge of the register, and then drawing the register forward and letting it rest, so that it is closed all but about 1½ in., it will be immediately found that one-fourth or one-third more heat is thrown into the room, for a similar result is brought about as with the modern projecting or overhanging brick backs, which cause the heat to be deflected forwards which would otherwise have passed directly up the chimney. If an existing stove of this description be fitted with a rack adjustment for the register flap and with an “economiser,” an advance of 30 to 40 per cent. in economy and comfort will be experienced, for in the ordinary manner in which these stoves are fitted and used, it can be taken that one-half the heat passes directly up the chimney; a good proportion of the heat radiated is drawn back by the current of air proceeding from the room towards and up the chimney; a proportion is lost by conduction, the heat being passed away to the walls and surrounding parts, and a fair proportion is lost by the smoke, which is really unconsumed fuel; but this form of stove is improving rapidly in various ways, as will be described hereafter.

_Open Stove._--This subject has been most ably discussed by Dr. Pridgin Teale, in connection with the economising of fuel in house fires. His remarks will well bear repeating.

“It is hardly possible to separate the two questions of economy of fuel and abatement of smoke. None who, in their own person, or as the companion or nurse of friends and relatives, have gone through the miseries of bronchitis or asthma in a dense London fog, can fail to perceive that this is a serious medical, not less than a great economical, question. Nine million tons of coal--one-fourth of the domestic fuel consumption in this kingdom--is what I estimate as a possible reward to the public if they will have the sense, the energy, and the determination to adopt the principles here advocated, and which can be applied for a very small outlay. Much has been said by scientific men about waste of fuel, and strong arguments have been advanced which make it probable that the most economical and smokeless method of using coal is to convert it first of all into gas and coke, and then to deliver it for consumption in this form instead of coal. Theoretically, no doubt, this is the most scientific and most perfect use of fuel, and the day may come when its universal adoption may be possible. But before that time arrives many things must happen. The mode of manufacture, the apparatus on a mighty scale, and the mode of distribution must be developed, nay, almost created, and a revolution must be effected in nearly every fireplace in the kingdom. At present its realisation seems to be in a very remote future. Meantime I ask the public to adopt a method which is the same in principle, and in perfection not so very far short of it. It is nothing, more nor less, than that every fireplace should make its own gas and burn it, and make its own coke and burn it, and this can be done approximately at comparatively little cost, and without falling foul of any patent, or causing serious disturbances of existing fireplaces. We must, first of all, do away with the fallacy that fires won’t burn unless air passes through the bottom or front of the fire. The draught under the fire is what people swear by (aye, and many practical and scientific men too), and most difficult it is to sweep this cobweb away from people’s brains. They provide 2 or 3 times as much air as is needed for combustion, ⅓, perhaps, being the necessary supply of oxygen, the remainder serving to make a draught to blow the fire into a white heat, and to carry no end of waste heat rapidly up the chimney; ⅔ of cold air chilling the fire, ⅔ more than needful of cold air coming into the room to chill it; and much of the smoke and combustible gases hurried unburnt up the chimney. The two views which I am anxious to enforce upon the attention of the public, of builders, of ironmongers, and of inventors, are these: that the open grating under the fire is wrong in principle, defective in heating power, and wasteful of fuel, and that the right principle of burning coal is that no current of air should pass through the bottom of the fire, and that the bottom of the fire should be kept hot. This principle is violated by the plan of closing the slits in the grate by an iron plate resting on the grate, which cuts off the draught, but allows the chamber beneath the fire to become cold, and when cinders reach the plate they become chilled, cease to burn, and the fire becomes dead. The right principle is acted upon by the various grates with fire-brick bottoms, and the English public owes much to the inventor of this principle as carried out in the Abbotsford grates, which have done much to educate the British public in the appreciation of the fact that a fire will burn well with a current of air passing over it, and not through it. But there is a better thing than the solid fire-brick bottom, and that is a chamber underneath the grating, shut in from the outer air by a shield resting on the hearth and rising to the level of the bottom bar of the range. This hot-air chamber, into which fine ash can fall, produces on the whole a brighter and cleaner fire, and one which is more readily revived when low, than the solid fire-brick. There is another mighty advantage in the principle of the ‘economiser’--an unspeakable advantage, it is applicable to almost every existing fireplace, and it need not cost more than 3-4._s_ This idea has now been long on its trial. It has been applied in hundreds of houses. It has been submitted to the very severe test of being applied to an infinite variety of grates, under a great variety of circumstances, and tried with coke, anthracite, and coal, good, bad, and indifferent. The effect has been, in an enormous number of instances, a marked success in saving coal and labour, and in more comfortable uniform warmth to the room. The failures have been very few indeed. I have drawn up 7 rules for the construction of a fireplace, all of which are pronounced to be sound:--

“1. As much fire-brick, and as little iron as possible.

“2. The back and sides of the fireplace should be fire-brick.

“3. The back of the fireplace should lean or arch over the fire, so as to become heated by the rising flame.

“4. The bottom of the fire or grating should be deep from before backwards, probably not less than 9 in. for a small room nor more than 11 in. for a large room.

“5. The slits in the grating should be narrow, perhaps ¼ in. wide, for a sitting-room grate, ⅜ in. for a kitchen grate.

“6. The bars in front should be narrow.

“7. The chamber beneath the fire should be closed in front by a shield or economiser.

“There is one caution which should be given. There is no doubt about the fact that immediately beneath the fire the hearthstone is hotter, and the ashes remain much hotter when the ‘economiser’ is used. This may increase the risk of fire whenever wooden beams lie under the fireplace. In any case of doubt, the best plan would be to take up the hearthstone and examine, and relay with safe materials; but should this be impossible, safety may be secured by covering the hearthstone with a sufficient thickness of fire-brick, just within the space enclosed by the ‘economiser’--leaving a space of 2 or more in. between the fire-brick hearth and the bottom of the fire. In lighting the fire, if there be no cinders on which to build the fire, it is well to draw away the ‘economiser’ for a short time until the fire has got hold; but, if there be cinders left from the previous day, on the top of which the paper and wood can be placed, then the fire may be lighted with the ‘economizer’ in its place. There is a great art in mending a fire. It is wasteful to throw lumps of coal higgledy-piggledy on the fire. The red embers should be first broken up so as to make a level surface, then pieces of coal should be laid flat on the fire and fitted in almost like pavement; lastly, if the fire is intended to burn slowly and last very long, small coal should be laid on the top. An ‘economised’ fire so made will, in a short time, heat the coal through, and give off gases, which will ignite and burn brightly on the surface of the black mass, and when the gases are burnt off there is a large surface of red-hot coke.”

The annexed illustrations show the application of the economiser. Fig. 30 is a kitchen range, _a_ being the economiser and _b_ the front damper. The latter should always be used in warm weather, unless the front of the fire is needed for roasting and should be put on at night. Fig. 31 is a bedroom fireplace having fire-brick sides _a_, fire-brick back _b_ leaning over the fire, narrow front bars _c_ movable, grating _d_ with narrow slits, chamber under the fire closed by economiser _e_, and front damper _f_ which can close the lower ⅔ of the front of the fire at night or when a slow fire is needed.

The “economiser” is a shield of sheet iron which stands on the hearth, and rises as high as the lowest bar of the grate, against which it should fit accurately, so as to shut in the space or chamber under the fire. If the front of the range be curved or angular, as in most register stoves, the economiser will stand, owing to its shape--but if the front be straight, the economiser needs supports such as are shown. “Ordinary economisers” are made of 16-gauge charcoal iron plate, with ⅜ in. bright steel moulding at the top, ½ in. moulding at the bottom, and 1 or 2 knobs as required. “Kitchen economisers” are made of 16-gauge iron, with ½ in. semicircle iron at the top edge; and with supports in scroll form of ½ in. semicircle iron. Some makers use rather thinner iron plate and give strength by the mouldings. Some have used too thin plates, little better than tin, which have warped and so become more or less useless. Great care should be spent in taking the dimensions--as every grate has to be measured--as a foot for a boot. This renders it almost impossible to send orders to a maker by post. Some skilled person must take the measure, and take it accurately. The dimensions to be taken are: firstly, the outline of the bottom bar of the grate. If it be curved, or angular, the outline can be well taken by a piece of leaden gas-pipe, which, moulded to the outline can then be traced upon paper or carried carefully away to the makers; secondly, the height must be measured from the hearthstone to the bottom bar. This is the “economiser” in its simplest and cheapest form, as applicable to nearly every ordinary range.

Ornament can be added to taste. It is obvious that the adaptation of the economiser need not displace the old-fashioned ash-pan, and that the two can be combined, or that the economiser may be made like a drawer and catch the ashes. All such variations will work well, provided that the main principles be adhered to of “cutting off the under current,” and “keeping the chamber under the fire hot.” But the simplest form is the best.

Fig. 32 illustrates a few typical specimens of modern improved open grates devised to increase the radiation of heat and perfect the combustion of the fuel: A is a combination of Parson’s grate and economiser with a Milner back; B is Nelson and Sons’ “rifle” back; C is a Galton back; D, Jaffrey’s grate.

“The Manchester Warming and Ventilating Grate” (E. H. Shorland, St. Gabriel’s Works, Manchester) is somewhat similar in principle to Captain Galton’s grate, i.e. the warm fresh-air inlet is at the ceiling, and the vitiated air is carried off by the chimney, or in some instances ventilation at a lower part of the room is provided. Fig. 33 will acquaint the reader with the details: _a_, fireplace; _b_, outer wall; _c_, inner wall; _d_, smoke flue; _e_, _f_, cold-air inlets; _g_, _h_, warm-air passages; _i_, inlet for cold or warm air into room.