274 



CASSELL'S POPULAR GAEDENING. 



of piping reqviired for heating a given area is one of 

 the most important points connected with the whole 

 system. At one time the inventors of toilers invari- 

 ahly wronged themselves and disappointed their 

 clients hy overrating the power of their apparatus — 

 boilers they can scarcely be called, as the water very 

 rarely boils, neither is it economical engineering to 

 allow or require it to do so. When the water in 

 a hot-house boiler reaches 212°, the boiling point, 

 either it is too small for its work, or the pipes are 

 badly set; indeed, to heat the water to 200° Fahr. the 

 pipes must have a very unsightly rise, and the 

 amount of driving would result in a terrible waste of 

 fuel. In order to obtaia the greatest amount of heat 

 from the smallest consumption of fuel, we should 

 employ a large range of piping at a comparatively 

 low temperature, rather than a small quantity of 

 piping worked at a high temperature. To determine 

 the length of piping required for a glass structure, 

 we must first of all ascertain the number of cubic 

 feet of air to be warmed per minute. This done, it 

 wUl be necessary to take into account the position of 

 the house — whether there is a large or small amount 

 of glass in proportion to the area ; whether it is a 

 span-roof or a snug lean-to against a south wall ; and 

 last, but not least, the position the pipes are to oc- 

 cupy. As heat naturally ascends, it is necessary to 

 plEice the pipes on a low level, but not so low as to be 

 removed from the fuU action of the atmosphere. 

 Generally they are placed opposite the ventilators, 

 sometimes in grating-covered areas, where, unless the 

 areas are thoroughly ventilated from the exterior, 

 two-thirds of the heat is lost. 



On reference to the excellent work by Mr. Hood, 

 we find the following table showing the length of 

 four-inch piping required to heat 1,000 cubic feet of 

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

 the pipe being 200°. 



To use the above table, look for the lowest external 

 temperature in the left-hand column, and at the top 

 for the highest temperature at which the house is to 

 be kept, and where the two columns intersect will be 

 found the number of feet of four-inch pipe which will 

 heat 1,000 cubic feet of air per minute to that de- 

 gree. It is, however, best to allow rather more. 



Hxample.—Take a house containing say 10,000 

 cubic feet of air which it is necessary to keep at 70°, 

 the external air being 32°. The figures at the angles 

 below 70° and opposite 32° are 164. Multiply this 

 sum by ten, and the result wiU be 1,640 feet of four- 

 inch piping. 



Position and Arrangement of Pipes. — 



Main Pipes. — Unless the house is very small it 

 rarely happens that the heating or radiating pipes 

 proceed direct from the boUer as in Fig. 46, but more 

 frequently from the "laina or carriers, from which a 

 number of houses or compartments can be heated. 

 Slain pipes should in all cases rise steadily from the 

 boilers ; they should never be allowed to dip, and if 

 possible sharp bends should be avoided. As many 

 people have an idea that several series of four-inch 

 pipes require a main whose area is equal to that of 

 all the branches, it may be well to state that this is 

 a fallacy which often leads to unnecessary expense, 

 followed by unsatisfactory results. Small mains, on 

 the other hand, which offer great resistance, should 

 in like manner be avoided, and the happy medium, 

 in all cases the best, decided upon. This, unless the 

 place is very large and complicated, will be secured 

 by the introduction of four-inch pipes, which may 

 rise quickly to the first part of their work, after- 

 wards the rise need not exceed half an inch in every 

 nine-foot length. 



Mains should always be protected from the in- 

 fluence of the atmosphere when placed above ground, 

 otherwise they will lose a great deal of heat. When 

 carried below the ground -line, as is generally the case 

 in gardens, brick areas, in which the pipes can be 

 supported or suspended, will be most suitable for theii 

 protection. The areas should be closely covered and 

 not ventilated, as a body of quiescent air is a good 

 non-conductor of heat. When so covered, facilities 

 for getting to the pipes should always be provided, 

 otherwise leaks will cause much unnecessary labour 

 and trouble in breaking up the ground to discover 

 them. 



In large gardens distinct sets of mains may be re- 

 quired to carry the water from two or more boilers, 

 working separately or together. Under this ar- 

 rangement every flow and return from the different 

 boilers should have patent stop-valves that can be 

 closed in case of accident to one of the boilers, when 

 the sound part of the apparatus can be kept at work 

 during repairs. 



Joints. — Many modes of making joints are now 

 in use, and being well understood by good workmen, 

 short reference here will suifice. Many who look 

 upon the screw-and-flange joints with vulcanised 

 india-rubber rings or washers as plebeian, cling to 

 the old cement joints. 



