Crown Boiler BWF Series Installation Instructions Manual page 25

7. Water Piping (continued)
2. Indirect Water Heaters - Figure 7.4 shows
typical indirect water heater piping. Boiler
piping is the same as for any two-zone system.
Figure 7.4 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.
3. Large Water Volume Systems - The piping
shown in Figure 7.5 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.
If the circulator is mounted on the supply, the
bypass must be on the discharge side of the
circulator.
109836-01 - 04/20
Figure 7.5: Boiler Bypass Piping
4. Low Temperature Systems - Some systems,
such as radiant tubing systems, require the
system water temperature to be limited to
a value below the temperature of the water
leaving the boiler. These systems also typically
have return temperatures well below the 120°F
minimum.
Figure 7.6 illustrates the use of a heat
exchanger to connect the boiler to this type of
system. The heat exchanger will permit the
transfer of heat from the boiler water to the low
temperature system while holding the system
supply and boiler return temperatures within
their limits. For this system to work properly the
heat exchanger must be properly sized and
the correct flow rates are required on either
side of the heat exchanger. Consult the heat
exchanger manufacturer for sizing information.
The water in the boiler is completely isolated
from the water in the system. This means that
separate fill and expansion tanks are required
for the heating system loop.
There are several other ways to connect low
temperature systems to the non-condensing
boilers like this one, such as four way mixing
valve and variable speed injection pumping
systems.
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