mechanical ventilation are the radiators, and in the design of the system the utmost consideration should be given to their selection and proportioning.
Radiators.—Radiators are made either of cast or wrought iron and are classified according to kind of heating for which they are used into direct, direct-indirect, and indirect radiators. A few years ago wrought-iron pipe made up with bends and headers into coils of various sizes and shapes was used very largely for radiators, and especially for indirect radiators; but on account of their greater economy of construction, cast-iron radiators are rapidly supplanting the wrought-iron pipes for all purposes. To-day wrought-iron pipe coils are used in direct heating where very large radiators are required spread over a large area of wall surface, such as in factory rooms or warehouses, where a series of long pipes connected into headers at each end are run along the walls, either over or under the windows, preferably under. Pipe coils are also used for large indirect radiators, but in this case, as a rule, only in connection with ventilating fans, as will be described in subsequent chapters.
Fig. 12Fig. 13Fig. 14
Flue Radiators.
The styles and kinds of cast-iron radiators are innumerable. They are made in sections or loops, which are fastened together
