A manual of home-making

Not only is the capacity of the fire pot important, but its depth should receive con.sjdemtiorK If the full-rateil load is to be carried without attention to the hiv for a Oiininium period of eight hours, the depth of the fuel-lied should be at least 12 inches. A heater that is to burn coke should i:*^* designed for a greater depth — probabty 24 inches — on account of the bulkiness of the fuel and the tlififerent combustion conditions required for burning it satisfactorily. In fact, one of the largest manufacturers of boilers for heating houses by steam or hot water now designs such f^HLiipment for a fuel-bed 18 inches deep when anthracite is to be used. Regarding the necessary size of fire pot, another detail that affects both economy and convenience of operation is the com- bustion space above the fuel-bed. Any unlmrnefl combustible gases that leave the fire pot are rapidly cooled in passing over the heat-absort]irig surfaces between the fire pot and the smoke pipe, and their temperature is quickly brought below that nec- essary for ignition. If either anthracite coal or coke is to be burned, a relatively small coml)Ustion space above the fuel- bed will be required because combustion takes place in or close to the fuel-befi If bituminous coal is to be used, however, more space should be provided for burning the combustible gases rising from the fuel-bed, or a considerable part of these I I 19(1 A MANUAL OF HOME-AfAKlNG gases will escape unburned, the flue surfaces will become coated with soot, and the lieat losses will be large. Another important detail, if bituminous coal is to be used, is the cross section for the gas passages between the fire pot and the smoke pipe. If the passages are not large enough, the draft may be cut down by the aceumulation of soot in the fines, possibly to siieh an extent that the fire will go out. Also, if bituriiinous coal is to l^e used, the flues should l>e of such size and so arranged as to invite frcs:itient anfl eas}^ cleaning. Obviously^ if the heater is sniollor than the proper size, fire at shorter intervals will be necessary, drafts will have to be kept open, and the temperature of the escaping gases will be higher than if a heater of proper size is installed — between 375*^ and 475*" F. in ordinary winter weather. The inconven- ience resulting from too h ili-r or fnmace is less than frani one under size, but * i idling will be necessary to control tlie fire satisfactorily in iiuld weather. Each heater IniB a particular capacity at. which its efficiency is highest » but if the heater be properly designed, within a cer- tain ra!;ge of capacity the efficiency will he practically eciual to the maximum. The equipment selected should be one that dur- ing most of the heating season will be operated within these hni- its, but will take care of maximum demands for a short time. Kind ofjud used.