Steam Heating

STEAM HEATING Steam heating is unlike hot-air heating in principle, as well as in results attained. In heating a room with hot air, the register distrib utes the heated air to the room, this warm air ascending to the ceiling, and then descending to the floor as it becomes heavier after cooling. A steam radiator circulates or turns the air in the room, as shown by Fig. 13. Note the down ward circulation of the cold air from the win dow, as indicated by arrows.

Weather conditions do not affect the effi ciency of steam-heating apparatus; with it, it is possible to heat any character of building, in any location, regardless of extremely low tem peratures or prevailing high winds, so long as these conditions have been provided for by the heating contractor.

The early method of steam heating was in accordance with the system. Many such plants, however, were noisy in operation, caused by in the system, this con dition being due to the faulty installation of the small piping used; and such plants were also often rendered inefficient by poor practice in making pipe connections. Water-hammer is caused by the presence of traps in the piping; that is, portions of the piping system are imper fectly drained of the water of condensation. When the fire is checked, and the piping and radiators cool, the portion of the water of con densation which has found lodgment in the piping or the radiators has also become cold. When steam is again generated at the boiler, the supply in passing this accumulation of cold water in the traps or pockets condenses rapidly, and this action causes water-hammer. To over come this trouble, it is therefore necessary that all steam piping, regardless of the particular system used, should be so erected as to insure perfect drainage in this respect.

In this connection the use of eccentric fit tings is advised. Fig. 14 shows a short part of a main steam line on which the ordinary styles of fittings are used and the size of main reduced, and also the identical piece again on which fittings tapped eccentric are placed. The perfect drainage afforded by the latter usage is at once apparent.

The modern low-pressure system of steam heating is usually a gravity job, the boiler or steam generator being placed below the level of the steam mains. While the two-pipe system is still at times advocated and employed, prac tically all of the installations of low-pressure steam heating in these days are erected by what is known as the one-pipe method. There are several adaptations of this method—namely, the "one-pipe circuit" system, the "divided-circuit" system, the "one-pipe system with dry returns," the "one-pipe system with wet returns," etc. These will be described later.

In planning for the installation of a low pressure steam-heating apparatus, it is neces sary to figure for each room to be heated the size of radiator needed to warm the space to the required temperature; and after the total amount of radiation necessary for the work has been determined, the next step is the selection of a suitable boiler.

Methods of Determining Radiation. The amount of radiation required depends upon three prevailing factors: (1) the size and loca tion of the room; (2) the square feet of its glass exposure (windows and outside doors counted as glass) ; and (3) the square feet of outside or exposed wall surface. Too many fitters and con tractors are using "rule of thumb" methods in calculating such requirements, thereby causing trouble and unsatisfactory results from installa tions of this character. Only such rules as are absolutely accurate should be used in figuring on work, and the two known as the "Baldwin" and "Mills" rules can be relied upon.

Baldwin Rule. The Baldwin rule for deter mining radiation is as follows: Divide the difference in temperature between that at which the room is to be kept and the coldest outside at mosphere, by the difference between the temperature of the steam in the radiator and that at which you wish to keep the room, and the result will be the square feet of radiating surface to be allowed for each square foot of "equivalent glass surface." Count each square yard of exposed wall as a square foot of glass to determine the former's equivalent in glass surface.