The heater differs from a steam boiler mainly in the omission of the space allowed for steam, the hot water heater being filled with water in circulation instead of steam, so that it is essential that the heat should strike the surface in such a manner as to increase the natural circulation.

Radiators for use with hot water differ from the ordinary steam radiators in having a passage at both bottom and top, as shown in the illustration, Fig. 67. This is necessary in order to draw off the air which gathers at the top of each loop. These radiators may be used for steam as well as hot water and are arranged for either top or bottom connections. Sometimes the piping is so arranged that, instead of running pipes to each radiator from the heater, a single riser is carried up to the expansion tank from which pipes are run to supply the drops to which the radiators are connected. (Fig. 68.) In this case the radiators are supplied at the top and emptied at the bottom, and as the air in this system rises at once to the expansion tank and escapes through the vent, no air valves are required on the radiators.

Other methods of heating are by indirect steam, indirect hot water, and a combination of hot air and steam, and the same general principles will apply to these methods as to those which have been considered. The indirect application of steam or hot-water is the system by which fresh air is brought to each register, after being heated by passing over a coil of steam or hot water pipes, and while it is the most satisfactory of all means of heating, the expense of installation and maintenance is a bar to its employment for ordinary country or suburban house heating

Fig. 66. Expansion Tank.

Fig. 66. Expansion Tank.

Fig. 67. Pipe Connections, Hot Water Radiator.

Fig. 67. Pipe Connections, Hot Water Radiator.

Inside Finish

After the furnace or heater is set and the plastering and concreting are thoroughly dry, the inside finish of the house may be put up. The door frames, which should have been all ready, will first be set and great care must be taken to see that these are set square and plumb. If a single rebated frame is used (Fig. 69a), the superintendent must see that it is set with the rebate on the proper side of the partition. Our specifications call for all inside door frames to be double rebated as at b, which not only does away with the necessity of this precaution, but has the merit of allowing the doors to finish at the same height and width on both sides of the partition and also allows of the door being hung on either side.

Fig. 68. Piping for Overhead Distribution.

Fig. 68. Piping for Overhead Distribution.