Navien NHB Series Installation & Operation Manual page 26

Maximum and Minimum Flow Rates through the Boiler
Model Minimum Pipe Diameter
NFB-301C
NFB-399C
Temperature Rise Conditions
20°F ΔT @ 100% water
Model
Flow Rate (GPM)
NFB-301C
NFB-399C
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
Flow Rate (GPM)
NFB-301C
NFB-399C
Model
Flow Rate (GPM)
NFB-301C
NFB-399C
Minimum Flow Rates through the Boiler for Use with Glycol
Model
For Use With 30% glycol
NFB-301C
NFB-399C
26 About the Boiler
1
1 / "
4
1
1 / "
2
Head (Ft)
29 10.5
39 4.3
20°F ΔT @ 30% glycol
Head (Ft)
32 12.6
42 5.2
20°F ΔT @ 50% glycol
Head (Ft)
35 14.7
46 6.0
Minimum Flow (GPM)
For Use With 50% glycol
11
13
Maximum Flow (GPM)
32
42
25°F ΔT @ 100% water
Flow Rate (GPM) Head (Ft)
24 7.4
31 3.0
25°F ΔT @ 30% glycol
Flow Rate (GPM) Head (Ft)
25 8.9
33 3.6
25°F ΔT @ 50% glycol
Flow Rate (GPM) Head (Ft)
28 10.4
37 4.2
12
14
Minimum Flow (GPM)
10
12
35°F ΔT @ 100% water
Flow Rate (GPM) Head (Ft)
17 4.0
22 1.8
35°F ΔT @ 30% glycol
Flow Rate (GPM) Head (Ft)
18 4.8
24 2.2
35°F ΔT @ 50% glycol
Flow Rate (GPM) Head (Ft)
20 5.6
26 2.5