Navien NFB Series - Piping Sizes and Considerations; Connecting Communication Cables; Configuring Communication Settings

65Installing a Cascade System
8.1.1 Piping Sizes and Considerations
When plumbing a cascade system, consider the following pipe
diameters and flow rates. Note that flow rates above 4 ft/s may
cause pipe erosion or velocity noise. These specifications may vary
depending on installation conditions.
NFB-175
Qty
Flow Rate (GPM)
@ 20°F ΔT
Recommended
Boiler Pipe Sizes (2-4 ft/s)
2 32.2 2"
3 48.3 2-1/2"
4 64.4 3"
5 80.5 3"
6 96.6 3-1/2"
7 112.7 3-1/2"
8 128.8 4"
9 144.9 4"
10 161 4"
11 177.1 5"
12 193.2 5”
13 209.3 5"
14 225.4 5"
15 241.5 5"
16 257.6 6"
NFB-200
Qty
Flow Rate (GPM)
@ 20°F ΔT
Recommended
Boiler Pipe Sizes (2-4 ft/s)
2 36.6 2"
3 54.9 2-1/2"
4 73.2 3"
5 91.5 3-1/2"
6 109.8 3-1/2"
7 128.1 4"
8 146.4 4"
9 164.7 5"
10 183 5"
11 201.3 5"
12 219.6 5"
13 237.9 5"
14 256.2 6"
15 274.5 6"
16 292.8 6"
8.2 Connecting the Communication Cables
Up to 16 boilers can be connected with Navien Ready-Link
communication cables. Select one of the boilers in the cascade
system as the main boiler, and then connect the other boilers to
it as sub boilers. Before making any connections, ensure that the
power is turned off to all boilers.
Connect the Ready-Link cables to the CNK1 terminal strip:
NC
NC
COM
NC
NC
COM
LWCO
AC24VL
AC24VN
NC
NC
COM
ZONE1ZONE2ZONE3
COM
NC
NC
ZONE1
COM
NC
NC
ZONE2
COM
NC
NC
ZONE3
AC24VN
SUPPLY RETURN OUTDOOR DHW TANK
AC24VL
LWCO
R
W
C
R
W
C
R
W
C
R
W
C
8.2.1 Configuring the Communication Settings
After connecting the Ready-Link communication cables, restore
power to the boiler and turn on all boilers using the Power button.
Refer to “11.4.4 Configuring a Cascade System” to configure the
communication settings.