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FIGURE 12: BOILER BYPASS PIPING
FIGURE 11: INDIRECT WATER HEATER
BOILER SIDE PIPING
Piping for Special Situations
Certain types of heating systems have additional requirements. Some of the more common variations follow:
1) Indirect Water Heaters - Figure 11 shows typical indirect water heater piping. Boiler piping is the same as for any two-
zone system. Figure 11 shows circulator zoning, which is usually preferred for indirect water heaters. Size the
circulator and indirect water heater piping to obtain the boiler water flow through the indirect water heater called for by
the indirect water heater manufacturer.
2) Large Water Volume Systems - The piping shown in Figure 12 will minimize the amount of time that the boiler operates
with return temperatures below 120°F on these systems. A bypass is installed as shown to divert some supply water
directly into the return water. The bypass pipe should be the same size as the supply. The two throttling valves shown
are adjusted so that the return temperature rises above 120°F during the first few minutes of operation. A three-way
valve can be substituted for the two throttling valves shown.
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