DIRECT-STEAM HEATING A system of direct-steam heating consists (1) of a furnace and boiler for the combustion of fuel and the generation of steam; (2) a system of pipes for conveying the steam to the radiators and for returning the water of condensation to the boiler; and (3) 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-pres sure of from 2 to 10 pounds is carried, and the condensation flows hack 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.
Types of Radiating Surface.
The radiation used indirect-steam heating is made up of cast-iron radiators of various forms, pipe radiators, and circulation coils.
15. Radiators of this type are made up of sections, the number depending upon the amount of heating surface required. Fig. 16 shows an intermediate section of a radiator of this type. It is simply a loop with inlet and outlet at the bottom. The end sections are the same, except that they have legs, as shown in Fig. 17. These sections are connected at the bottom by special nipples, so that steam entering at the end fills the bottom of the radiator, and, being lighter than the air, rises through the loops and forces the air downward and toward the farther end, where it is dis charged through an air-valve placed about midway of the last section. There are many different designs varying in height and width, to suit all conditions. The wall pattern shown in Fig. 18 is very con
venient when it is desired to place the radiator above the floor, as in bathrooms, etc.; it is also a venient form to place under the windows of halls and churches to counteract the effect of cold down drafts. It is adapted to nearly every place where the dinary direct radiator can be used, and may be connected up in different ways to meet the rious requirements.
A low and moderately shallow radiator, with ample space for the circulation of air between the sections, is more efficient than a deep radiator with the sections closely packed together. One and two-column radiators, so called, are preferable to three and four-column, when there is sufficient space to use them.
The standard height of a radiator is 36 or 38 inches, and, if possible, it is better not to exceed this.
For small radiators, it is better practice to use lower sections and increase the length; this makes the radiator slightly more efficient and gives a much better appearance.
To get the best results from wall radiators, they should be set out at least 11 inches from the wall to allow a free circulation of air back of them. Patterns having cross-bars should be placed, if possible, with the bars in a vertical position, as their efficiency is impaired somewhat when placed horizontally.