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Rh lem in itself, and is entirely subject to local conditions. The main, connections to the heating system must be laid out in connection with the exhaust and live-steam pipes of the power plant, according to the principles established in Chapter II. Simplicity in n piping system is always primarily desirable, but sufficient valves and by-passes should be installed, so that if any accident occurs to one part of the system that part can be shut off without crippling more than a small section.

Figure 45 shows the arrangement of the main piping connections in a large office building in Syracuse, N. Y., in which, on account of the extreme difference in floor levels and the crowded condition of the machinery, a really systematic arrangement of piping it was impossible to obtain. (The Engineering Record of November 5, 1898.) The main valves controlling the heating sys-



tern are indicated at A, B, C and D. During the heating season the valve, D, is opened and the back-pressure and reducing-pressure valves put into service, while during the summer months the valve, D, is closed entirely, shutting off the heating mains, and the 10-inch back-pressure valve is opened wide. Ordinarily, both in winter and summer, the valve, A, is closed, so that all exhaust steam from the pumps and engines goes through the muffler tank and heater; but in case it is necessary to' open these for cleaning, the valves B and C are closed and the valve, A, opened, so that the exhaust steam may go directly either into the free exhaust or the heating system, as the case may be. The building in question contains about 15,000 square feet of radiators and is heated on a two-pipe system with basement mains. The returns come back to the two automatic governors which control the 6x4x6-