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16
G. Circulator Sizing
In addition, the boiler heat exchanger has a minimum total water volume that must be taken into account when sizing the circulator. Minimum
boiler flow rates are listed in the table below.
Model
500
700/850
Table 4 - Minimum Flow Rates
The boiler heat exchanger does have a pressure drop which must be considered in system design. Refer to the graph in Table 5 for pressure
drop through the boiler heat exchanger.
Table 5 - Heat Exchanger Pressure Drop
The chart below represents various system design temperature rise through the boiler along with respective flows and friction loss. This is
provided to aid in circulator selection.
Model
Friction Ft
500
19'
700/850
35'
Table 6 - Temperature Rise, Friction Feet, and Flow Rate
whl-445 Rev. 000 Rel. 014 Date 7.21.20
Minimum Boiler Flow Rates
500 Model
System Temperature Rise Chart
20°Δt
Flow Rate (GPM)
Friction Ft
50
11'
85
26'
Minimum Flow (GPM)
33
54
700/850 Models
25°Δt
Flow Rate (GPM)
Friction Ft
40
65
30°Δt
Flow Rate (GPM)
8'
33
18'
54
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