Hot-water Supply

The term “central heating” applied to the heating of domestic and other buildings indicates that the whole of a building is heated from a central source, usually an independent boiler, fired by solid fuel, gas, electricity or fuel oil.

In general, a heating system should be designed so that the water will circulate by gravity. In some installations, circumstances are such that a pump or accelerator must be used to achieve a satisfactory circulation. This should be avoided if possible.

When designing a heating system for a large building, it is usual – in the interests of economy and to ensure efficient heating – to first calculate how much heat will be needed to maintain the building at the desired temperature. Then the size of the boiler and the amount of pipe and radiator heating surface required to give out this heat will be estimated. For small systems, “rules-of-thumb” methods and past experience are generally a sufficient guide.

A steam, or a hot water heating plant consists essentially of the radiators, the boiler and the system of piping connecting the former with the latter. Steam or hot water from the boiler is circulated through the piping and radiators: in these the steam condenses giving up its latent heat and the water given up some of its heat, thus warming the rooms. In the usual hot water installation, the boiler, pipes and radiators are kept full of water at all times, an expansion tank being provided to compensate for the increase in volume of water when heated and to prevent explosions in case of generation of too much steam.

Boilers. The boiler is usually placed at the lowest available point in the building, having regard at the same time to the convenience of stoking and delivery of fuel.

The boiler may be one of a number of types. It may be solid one-piece casting, rectangular in form; it may be sectional; or it may be conical in shape and wrought or cast iron. For smaller systems, the first and last-named types are both cheap and suitable. The sectional boiler has the advantage of the possibility of added sections should more heat be needed subsequent to initial installation.

System of piping. For steam heating the systems of piping usually employed are the ordinary one-pipe system and two-pipe system. In the former, but one connection is made to each radiator, this connection serving both as inlet for the steam and an outlet for the water of condensation. In the latter, there is a supply pipe and a return pipe for each radiator. The two-pipe system is expensive, and hot used generally in steam heating except for indirect radiators which must always have two connections in order to function properly.

In hot-water heating, although one-pipe systems may be used, it is considered the best practice to have a supply pipe and a return pipe for each *****les and tables for computing the size of pipe for both system and hot water heating will be found in handbooks.

In selecting a heating plant for residences there must be considered the size, the type of building, the climate and the first cost of operation.