WHL-038 Rev. 1.29.16
17
Minimum Boiler Flow Rates
Model
Minimum Flow (GPM)
750
7.5
1000
10
Table 3 - Minimum Flow Rates
Table 4 - 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)
750
2.85’
75
1.8’
60
1.3’
50
1000
1.85’
100
1.25’
80
0.8’
66.6
Table 5 - Temperature Rise, Friction Ft 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 4
for pressure drop through the boiler heat exchanger.
G. Circulator Sizing