HEATING. 



221 



proved Conical, the Independent Dome -top 

 Cylindrical, the Manchester (fig. 290), and the 

 Star Independent. These vary in height and 

 heating power, but one 4 feet in height will 

 heat about 1000- feet of 2-inch pipe. For still 



Fig. 201.— The "Halifax" Boiler. 



smaller houses the Halifax (fig. 291) is a useful 

 little boiler. 



For the setting of hot- water boilers fire-bricks 

 only should be used, and no stone or iron should 

 be exposed to the fire except the parts contain- 

 ing water, for they will soon burn away, espe- 

 cially if coke is used as fuel. Fire-bricks not 

 only do not burn out so rapidly as common 

 bricks, but they economize fuel. 



Pipes are generally made of cast-iron, but 

 other materials are sometimes employed. Copper 

 pipes are much used in France, and they have 

 the advantage of heating quicker than those of 

 cast-iron; but, on the other hand, they sooner 

 become cold if the fire is not kept up, and this 

 is often a disadvantage. The usual diameter of 

 pipes is 4 inches, and this being found to be the 

 most convenient and efficient size, calculations 

 for length of pipe are usually made according 

 to that diameter. In the case of small struc- 

 tures 2-inch and 3-inch pipes are preferable on 

 account of their occupying less space. 



The pipes, whatever may be their size and 

 form, should be of uniform bore or capacity; 

 and where valves are employed, they should be 

 so constructed as to afford at pleasure a clear 

 water-way equal to that of the pipes. Contrac- 

 tions and bends tend to obstruct the circula- 

 tion; the former may be avoided, and of the 

 latter there should be as few as possible. It is 

 necessary that a small tube be inserted at the 

 highest part of the flow-pipe, in order to provide 

 for the escape of any air which may collect at 

 that point. 



To allow for expansion and contraction, the 

 pipes should be slung or otherwise supported in 

 a manner that will permit them to accommodate 

 themselves to these forces. According to the 

 experiments of General Roy cast-iron expands 

 -yJ T between the freezing and 

 boiling points of water, or about 

 14 inch in 100 feet. 



With regard to the joints of 

 pipes, some prefer those which 

 are flanged and screwed together 

 with vulcanized india-rubber 

 washers; others prefer socket- 

 joints. The latter occupy less 

 space, the former can be more 

 easily removed and replaced. 

 Except near the fire, socket- 

 joints need not be put together 

 with iron cement, especially 

 when the circulation is carried 

 on nearly on a level. When well 

 caulked with rope and a mixture 

 of red and white lead, we have not in many 

 years observed a single failure. By kindling a 

 fire under the joints secured in this way, the 

 pipes, if wanted elsewhere, can be separated 

 without breakage, which can rarely be done 

 when iron cement has been employed. 



The quantity of pipe requisite for heating a 

 house depends on the size and form of the house, 

 the extent of the surface of glass, and whether 

 the roof is cf iron and glass, or of wood and 

 glass, and the temperature required. 



Warming Buildings by Hot Water. — Mr. Hood 

 calculates the quantity of air to be warmed per 

 minute at 1J cubic foot for each square foot of 

 glass, deducting, as a general rule, ^ for wood- 

 work; and he gives the following rule for 

 ascertaining the length of pipe which will be 

 necessary for warming any given quantity of 

 air: — "Multiply 125 by the difference between 

 the temperature at which the room [or hot- 

 house] is purposed to be kept when at its maxi- 

 | mum, and the temperature of the external air, 

 and divide this product by the difference be- 

 tween the temperature of the pipes and the 

 proposed temperature of the room: then the 

 quotient thus obtained, when multiplied by the 

 number of cubic feet of air to be warmed per 

 minute, and this product divided by 222, will 

 give the number of feet in length, of pipe 4 inches 

 diameter, which will produce the desired effect ". 

 He gives the following table, showing the 

 length of 4-inch pipe needed to heat 1000 cubic 

 feet of air per minute to from 45° to 90°, the 

 temperature of the pipe being 200° : — 



