Document qmXde19qnQ2b4Qdya2364KG05

682 CHAPTER 29 1956 Guide Fig. 4. Steam Supply Installation with Header for Process and .. Zone Connections various heating zones and process equipment. If initial pressure is below 50 psi the first stage pressure-reducing valve may be omitted. Heat supply should be graduated according to variations in the outside tem perature. The maximum in economical operation and satisfactory heating can only be obtained by the use of automatic temperature control (see Chapter 39). Rapid draining and venting of the heating system should be obtained by 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 21. Suggested trap capacities are given in Table 4. Provision should be made for conveniently shutting off the steam supply at night and at other times when heat is not needed. A considerable amount of heat can be saved by shutting off steam at night and other times when optimum building temperatures are not required. It is necessary, how ever, to have an ample amount of heating surface in order- that the build ing may be quickly warmed after such turn-off periods. Residual heat in the condensate should be salvaged. This heat may be salvaged by means of an air-cooling coil, or as is more frequently done, by a District Heating 683 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, KTERMfTTEWT TYPE TRAP WiTH THERMOSTATIC ELEWCNT Tf*-FLOAT TYPE AIR CONDENSATE OUTLET-- A TYPICAL CfiAffTY INSTALLATION C0ACMATO4- FLOAT AND TNCRMOS1XTC TRAP CONDENSATE CRAM PIPE SAAC SIZE AS NCTER OUTLET- CONDENSATE OUTLET-- B ORRffTY INSTALLATION USING RECEIVER NOT LESS THAN 24 LONG SANC. SIZE OR LARGER than ACTER OUTLET- CONDENSATE DRAM PPZ SAME SIZE AS METER CUTLE1 C VACUUM MSttULUQTOH WITH MASTER TRAP TO VACUUM PLMPD VACUUM M5TALLATT0N. WTTHOUT MASTER TRAP Msteb Capacity Lb Peb Hb 250 500 750 1500 3000 6500 A--Dimension Inches Diagram B........................ 4 4 8 8 8 12 Diagram D............... --------------------------------------------------------------- 12 12 12 12 15 15 15 15 15 15 18 18 Fig. 6. Condensate Meter Installation Details 12000 12 18 18 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 the storage tank. METERING Meters are classified into two groups: Condensate Meters and Flow Meters. The Condensate Meter is a popular type for use where all the condensate can be brought to a common point for metering purposes. Its simplicity