24 Installing the System Piping
Pump Sizing for Use with Glycol
The use of glycol results in a greater head loss due to its higher viscosity compared to water. Heat transfer is
also reduced as the glycol concentration increases. The corrected flow rate and head loss values below must be
used when sizing the boiler pump in order to maintain similar performance as using 100% water for the heating
system. Refer to the chart below.
Model
20°F ΔT @ 30% glycol
25°F ΔT @ 30% glycol
35°F ΔT @ 30% glycol
Flow Rate
(GPM)
Head
(Ft)
Flow Rate
(GPM)
Head
(Ft)
Flow Rate
(GPM)
Head
(Ft)
NFB-175H
17
6.0
14
4.0
10
2.2
NFB-200H
20
7.7
16
5.0
11
2.6
Model
20°F ΔT @ 50% glycol
25°F ΔT @ 50% glycol
35°F ΔT @ 50% glycol
Flow Rate
(GPM)
Head
(Ft)
Flow Rate
(GPM)
Head
(Ft)
Flow Rate
(GPM)
Head
(Ft)
NFB-175H
19
8.5
15
5.6
11
2.9
NFB-200H
22
11.1
17
7.0
12
3.8
Minimum Flow Rates through the Boiler for Use with Glycol
Model
Minimum Flow (GPM)
For Use With 30% glycol
For Use With 50% glycol
NFB-175H
7.5
8.3
NFB-200H
8.6
9.5
Note
If the flow rate is below the required value for the specific boiler model as shown on the chart, it may
result in noise and/or potential damage to the boiler.
Summary of Contents for NFB-175H
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