lp-445-r4 Rev. 006 Rel. 027 Date 7.21.20
16
Minimum Boiler Flow Rates
Model
Minimum Flow (GPM)
500
33
700/850
54
Table 4 - Minimum Flow Rates
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.
System Temperature Rise Chart
20°Δt
25°Δt
30°Δt
Model
Friction Ft
Flow Rate (GPM)
Friction Ft
Flow Rate (GPM)
Friction Ft
Flow Rate (GPM)
500
19’
50
11’
40
8’
33
700/850
35’
85
26’
65
18’
54
Table 6 - Temperature Rise, Friction Feet, and Flow Rate
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.
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.
G. Circulator Sizing
