This section is from the book "The Principles And Practice Of Modern House-Construction", by G. Lister Sutcliffe. Also available from Amazon: How Your House Works: A Visual Guide to Understanding & Maintaining Your Home.
The Grundy Grate is somewhat similar to the Galton grate, and is shown in Plate XVII. The fresh-air opening through the outer wall is shown at a, or, if more convenient, it can be put lower down as at b, or carried as a channel along the skirting-board or below the floor-txxards in either direction. The cold air, entering this flue, passes under the cast-iron base-plate c. If the inlet is at B, the air reaches the warm-air chamber D round the back of the fire-grate, and passes into the room through the warm-air duct H, which has a regulating valve K. The grating itself is lettered f, and the bars g, while the whole of the back of the fire consists of firebrick, marked E. This grate is made in various sizes with various heating capacities. It is obvious that the condition of the warm air entering the room will be, so far as purity is concerned, exactly the same as the external air, and if this is charged with soot, dust, or fog, these matters will be delivered into the room. In the grates described no arrangement is made to purify the incoming air, and while such fireplaces may be suitable for country-houses, they may not be satisfactory for town-houses. Another point is that, in order to obtain economy in the use of the fuel, it is desirable to block up the space between the grate and the hearth, but this point will be specially brought out in dealing with the following type of grate.
Fig 458 section of the Galton Independent More a a. fresh-airflues b b, smoke-flue. c c, fire-clay.
1 The fire-clay, howerer. will mora easily crack and to admit the smoke into the air-flues.- 1 ED.
Grundy's Warm-Air Ventilating Fire-Grate
A. Fresh Cold-air Inlet Grating.
B. Fresh Cold-air Inlet Grating
C. Cast-iron Base Plate.
D. Warm-air Chamber.
E. Firebrick Back.
F. Bottom (irate.
G. Front Bars.
H. Warm air Duct.
J. Warm-air Outlet Grating.
K. RegulatingValve. L. Cast iron Mantel. M. Cast iron Sealing Plate. N. Brickwork Slope. O. Smoke Flue.
The Teale Grate owes its design, io the first instance, to Mr. Pridgin Teale, F.R.S., a well-known Leeds surgeon. He was convinced that the waste of fuel by incomplete combustion could be easily lessened, even in an ordinary fireplace, if due precautions were taken by means of simple and inexpensive additions.
Fig 460. - Vertical Section of Teale Fire-grate.
Fig. 459 is a front elevation of one of his grates, showing the thin vertical bars, and the economizer, consisting merely of a metal plate fitted in front. Fig. 460 is a sectional elevation, and Fig. 461 a sectional plan. The points which Mr. Teale strongly insists upon are these: no air must be allowed to pass in below the grate at all; the space below the grate must be made into a closed hot chamber by means of the economizer; the slits in the grating itself should be made as narrow as possible, and the front bars should be as thin as possible. The whole of the air, therefore, which reaches the fire, arrives at or above the level of the fire, and he considers it desirable to have a solid band, about l¼ inches deep, at the bottom of the bars to hide from view the cinders and dust which are produced. The bottom of the grate should be deep from back to front, probably not less than 9 inches for a small room, or more than 11 inches for a large room. The inventor also lays stress upon the necessity for keeping all iron away from the fireplace, and proceeds to describe the best form for the fire-brick walls and sides as follows: -
Fig . 461 - Plan of Teale Fire-grate.
"The Mdes or 'covings' of the fireplace should be vertical, but inclined to one another as the sides of an equilateral trjangle, the apex of which would be behind the- fireplace. and the base would be in a line with the front. The work-in.: out of this rule has cost me much thought and experiment. It was worked out more or less empirically with a view to obtain certain objects, and having attained them I discovered that I had unwittingly selected the sides of an equilateral triangle. It La of some importance, and may be of interest, to tell how the question arc In my earlier fireplaces, the sides or 'covings' were parallel to each other, and had the- defect that they radiated most of their heat from one to the other, not into the room, with the probable result that much of such heat would eventually escape up the chimney. It was clear, then, that the sides must be set at an angle with the back, so as to face towards the room. But at what angle? My first experiments were determined by the shape of the corner bricks which were in the market. These determined the inclination of the sides to be such that, if prolonged backwards, they would meet at a right angle. This is the angle laid down by Rumford as the angle of selection, but as the largest angle admissible in a good fireplace. This angle, however, brought me into difficulties with my 'lean-over' back. The openness of the angle made. the back, as it ascended and inclined forwards, spread out so rapidly, that what was gained in width was lost in height. Moreover, my critics objected to its appearance as ugly. What then should determine the inclination of the sides? The point was thus determined. Seeing that a heated brick throws off the greatest amount of radiant heat at a right angle with its surface, the 'covings' should be at such an inclination to each other, that the perpendicular line from the inner margin of one 'coving' should just miss the outer margin of the opposite 'coving'. Where the 'covings', as in my earlier attempts and in Count Rumford's fireplaces, are at a right angle to each other, this perpendicular line misses the opposite margin by several inches. It was clear, therefore, that the inclination might be made more acute. Guided by this idea, and having determined the principle on which the shape of the grate should (Upend, an inclination was arrived at which turned out to be an angle of 60*, i.e. the inclination of the sides of an equilateral triangle.
"Commencing at a level a, corresponding with the top of the front bars, and leaning forward at an angle of 70° with the horizontal line of the hearth, the back should rise to such a point, that the angle where it returns towards the chimney B should be vertically over the insertion c of the eheeks of the firegrate. This angle B will be about 28 inches from the hearth, or 16 belies from the top of the fire, and about 3½ to 4½ inches from the front line of the fireplace, according to the size of the grate." These points will he obvious from the vertical section of the fireplace given in Fig. 460, and from c in Fig. 461.