Navien NFB Series User Manual

23Installing 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-175 17 6.0 14 4.0 10 2.2
NFB-200 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-175 19 8.5 15 5.6 11 2.9
NFB-200 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-175 7.5 8.3
NFB-200 8.6 9.5

Navien NFB Series Specifications

General

Type	Condensing Boiler
Fuel Type	Natural Gas or Propane
Heat Exchanger	Stainless Steel
Vent Type	Direct Vent
Vent Diameter	2" or 3"