This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Direct steam heating is used in all classes of buildings, both by itself and in combination with other systems. The first cost of installation is greater than for furnace heating but the amount of fuel required is less, as no outside air-supply is necessary. If used for warming hospitals, schoolhouses or other buildings where ventilation is desired, it must be supplemented by some other means for providing warm fresh air. A system of direct steam heating consists of a furnace and boiler for the combustion of fuel and the generation of steam; a system of pipes for conveying the steam to the radiators and for returning the water of condensation to the boiler; and radiators or coils placed in the rooms for diffusing the heat.
Various types of boilers are used, depending upon the size and kind of building to be warmed. Some form of cast iron sectional boiler is commonly used for dwelling houses, while the tubular or water-tube boiler is more usually employed in larger buildings. Where the boiler is used for heating purposes only, a low steam pressure of from 2 to 10 pounds is carried and the condensation flows back by gravity to the boiler which is placed below the lowest radiator. When, for any reason, a higher pressure is required, the steam for the heating system is made to pass through a reducing valve and the condensation is returned to the boiler by means of a pump or return trap. The methods of making the pipe connections between the boiler and radiators vary for different conditions and in different systems of heating. These will be taken up later under the head of design.
Direct radiating surface is made up in different ways: Fig.2 shows a common form of cast iron sectional radiator; these can be made up in any size depending upon the height and number of sections used. Fig. 3 is made up of vertical wrought iron pipes screwed into a cast iron base and is a very efficient form. Fig. 4 shows a type of cast iron wall radiator which is often used where it is desired to keep the floor free from obstruction. Fig. 5 is a special form of dining-room radiator provided with a warming closet. Wall and ceiling coils of wrought iron pipe are often used in school rooms, halls and shops or where the appearance is not objectionable.