Navien NR-180 Installation Manual page 44

Gas Water Heater Installation
5. Cascade system Plumbing Pipe Size (@ NR/NP-240(A))
△T=86 ºF
Q'ty
Flowrate
(GPM)
1 7.19
2 14.38
3 21.57
4 28.77
5 35.96
6 43.15
7 50.34
8 57.5
9 64.72
10 71.92
11 79.11
12 86.30
13 93.49
14 100.68
15 107.87

If the flow rate inside pipes is over 6.6 ft/s, corrosion might be occurred
inside the pipes.

Above state may be different depending on installation circumstance.
44
Velocity Pipe
of Water Diameter Q'ty
(ft/s) (mm/in)
3/4"
4.78 20A 16
1"
5.61 25A 17
11/4"
5.54 30A 18
5.21 40A 11/2" 19
11/2"
6.53 40A 20
2"
4.49 50A 21
2"
5.24 50A 22
2"
6.00 50A 23
21/2"
4.39 65A 24
21/2"
4.75 65A 25
21/2"
5.34 65A 26
21/2"
5.84 65A 27
21/2"
6.33 65A 28
21/2"
6.79 65A 29
3"
5.11 80A 30
△T=86 ºF
Velocity Pipe
Flowrate of Water Diameter
(GPM) (ft/s) (mm/in)
115.07 5.44 80A
122.26 5.81 80A
129.45 6.14 80A
136.64 6.46 80A
143.83 6.83 80A
151.02 4.06 100A
158.21 4.25 100A
165.41 4.45 100A
172.60 4.65 100A
179.79 4.85 100A
186.98 5.05 100A
194.17 5.24 100A
201.36 5.44 100A
208.56 5.61 100A
215.75 5.81 100A
3"
3"
3"
3"
3"
4"
4"
4"
4"
4"
4"
4"
4"
4"
4"