Document xN10Y4MVb1qrOJkEGa17j1BE

730 CHAPTER 28 1957 Guide means of suitable traps and air vents in order to obtain rapid circulation and quick heating. This is particularly important with intermittent-type temperature-control equipment. The selection of traps is discussed in Chapter 20. Suggested trap capacities are given-in Table 4 of this Chap ter. To obtain efficient and economical operation of any system it is im perative that all traps be properly maintained. In a system supplied with district steam any leakage through traps may prevent air removal from the District Heating 731 Table 4. Suggested Capacity of Pressure-Regulating Valves and Traps Type op Control Pressure-Regulating Trap Capacity. Lb/(Hb) Valve Capacity. Lb/(Hb) (Sq Ft op Pipe and (Sq Ft op Radiation*) Radiation*) Continuous or modulating operation, intermit tent with on periods over 3 hr in duration Intermittent operation with on periods of H to 3 hr in duration Intermittent operation with on periods of Yi hr or less H H W H H Hb Square Feet EDR. " Except for drip traps on which should be 1 lb per sq ft EDR. 0 Except for 1 pipe systems or 2 pipe systems not orificed wnich should be 1 lb per sq ft EDR- salvaged by means of an air-cooling coil, or as is more frequently done, by a water-heating economizer, shown in Fig. 5, which preheats the hot water supply to the building. The condensate from the heating system, after leaving the traps, passes through the economizer. The water supply to the heater passes through the economizer, absorbing heat from the condensate. If the hot-water system in the building is of the recirculating type, the recirculating line should be connected between the economizer and the water heater proper, not at the economizer inlet, because the recirculated hot water is itself at a high temperature. - Since the heating-system load and the hot-water demand are not coinci dent a greater amount of heat can be extracted from the condensate if storage capacity is provided for the preheated water. Frequently, there fore, the economizer coils are submerged in a storage tank. Where con densate is pumped, the pump should discharge into a receiving tank- 1. Service Pipe from District Steam Main 2. Motorized Pilot on Pressure-Regulating Valve 3. Bucket Trap on Header Drip Line , Note : Where process equipment is individually controlled, temperature control on header may be onuttefl. All fittings should be American Standard Class 250 cast iron or 3000 lb steel in both reduction and regulation assemblies. Fig. 4. Steam Supply Installation with Headeh for Process and Zone Connections system and otherwise impair its operation. Further more, such steam must be condensed and its condensate cooled before being discharged to sewer. This represents a direct waste of steam. Provision should be made for conveniently shutting off the steam supply night and at other times when heat is not needed. A considerable amount ol heat can be saved by shutting off steam at night and other times when optimum building temperatures are not required.20 Equipment is avail able which will automatically shut heat off at night for varying lengths o time, depending upon outside temperature.21 Residual heat in the condensate should be salvaged. This heat may he with all returns properly trapped or pur Qiacharge from vacuum system. With vs uum system a receiving tank with therm 2 event should be provided at Point / oteam Supply to Water Heater 3. Hot Water Supply to Building 4. Recirculating line 5. City Water Line 6. Pressure-Regulator Temperature Control Aa* sembly With Bypass 7. Thermostat Bulb and Tubing *'IG- 5. Method of Installing a Water Heater and Economizer in a Gravity Heating System