PB Heat Gas/Oil Boilers - Manual (Page 25)

control valve and boiler circuit pump piped off of
the system as a secondary loop. See Figure 3.6
for a single boiler and Figure 3.7 for multiple
boilers.
D. CHILLED WATER SYSTEMS
1. If the boiler will be used in conjunction with a
refrigeration system, the chilled medium must be
placed in parallel with the boiler and proper valves
applied to prevent the chilled medium from entering
the boiler. See Figure 3.5.
E. HIGH FLOW RATE PIPING
1. For flow rates higher than given in Table 3.1, provide
bypass piping around the boiler to limit the boiler
flow to that given in the table or pipe the boiler in a
secondary loop with its own pump as shown in
Figure 3.3.
F. MULTIPLE BOILER INSTALLATIONS
1. For multiple boiler installations, piping the boilers in
a secondary loop is recommended. Each boiler
should be provided with its own pump and piped off
of the secondary loop header. See Figure 3.7 for
systems with return temperature above 130°F on gas
boilers or 150°F on oil boilers. For low temperature
systems, see Figure 3.4 (constant low temperature
systems) or Figure 3.8 (variable low temperature
systems).
2. You can use alternative piping if desired, such as
parallel piping or series piping in the primary system
loop. But these systems are less versatile.
a) With parallel piping, for instance, the system flow
conditions change if one or more of the boiler
shut-off valves are closed. It is difficult to pipe
parallel boilers to protect the boiler from low
return temperatures.
b) With series piping, temperature control to the
system is difficult because the temperature rise
equals the sum of the rises through each boiler.
Series piped boilers cannot be isolated for
servicing.
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PIPE THE BOILER
Figure 3.5: Piping to Isolate Boiler from Chilled Medium on Chiller Systems