Document 71J7Bqp8ZO3Vaz32G4V4LbEQa

American Society of Heating and Ventilating Engineers Guide, 1934 to accommodate miscellaneous other services, such as for underground passage between buildings. SERVICE CONNECTIONS Most district heating companies enforce certain regulations regarding the consumer's installation, partly to safeguard their own interests but principally to insure satisfactory and economical service to the consumer. There are certain fundamental principles that should be followed in the design of a building heating system which is to be supplied from street mains. Although some of these apply to any building, they have been demonstrated to be especially important when steam is purchased. 1. Provision should be madefor conveniently shutting off the steam supply at night and at other times when heat is not needed. It has been thoroughly demonstrated that a considerable amount of heat can be saved by shutting off steam at night. Although there is, in some cases, an increased consumption of heat when steam is again turned on in the morning, there is a large net saving which may be explained by the fact that the lower inside temperature maintained during the night obviously results in lower heat loss from the building, and less heat need therefore be supplied, Steam can be entirely shut off at night in most buildings even in very cold weather without endangering plumbing. It is necessary, however, to have an ample amount of heating surface so that the building can be quickly warmed in the morning. Where the hours of occupancy differ in various parts of the building, it is good practice to install separate supply pipes to the different parts. For example, in an office building with stores or a restaurant on the first floor which are open in the evening, a separate main supplying the first floor will permit the steam to be shut off from the remainder of the building in the late afternoon. The division of the building into zones each with a separately controlled heat supply is sometimes desirable, as it permits the heat to be adjusted according to variations in sunshine and wind. 2. Residual heat in the condensation should not be wasted. This heat may be salvaged by means of a cooling radiator as illustrated ' in Fig. 2, or, as is more frequently done, by a heat exchanger which pre heats the water used for lavatory purposes, as in Fig. 3. Figs. 2 and 3 show'the practice of a Boston utility as to the service arid meter con nections. Fig. 4 shows a typical installation for service from the system of a New York utility. The condensation from the heating system, after leaving the trap, passes through the preheater on its way to the meter. The supply to the -hot water heater passes through the preheater, absorbing heat from the condensation. If the hot water system in the building is of the recircu lating type, the recirculating connection should be tied in between the preheater and the water heater proper, not at the preheater inlet, because the recirculated hot water is itself at a high temperature. The number of square feet of heating surface in the preheater should be approximately equal to one per cent of the equivalent square feet of heating surface in the building. 526 In s ta ll Service Pressure and Low Pressure Reducing Valves Fig. 4. T ypical Service nstallationI Chapter 36--District Heating 527