83
Installing a Cascade System
●
When linking multiple water heaters to NFC-H combi-boiler, only the main unit can provide space heating and
sub units must be configured for DHW only (You can set only the NFC-H combi-boiler as the main unit in the
cascade system, and the main unit controls the power on/off status of all the sub units in the system).
●
Once turned on by the main unit, the water heaters will operate in stages to satisfy the DHW demands.
●
After completing the cascade settings and saving the changes, the boiler and water heater units must be
turned off then turned back on for the changes to take effect.
●
If errors occur while operating a cascade system, the relevant errors are displayed in the display of the failing
unit.
●
Power supply to the units must be OFF during the system piping.
Note
●
The recommended recirculation flow rate for each water heater is 2-4 GPM. Depending on the
number of water heaters and the diameter of the recirculation line, it may not be necessary to
connect all the NPE-A2 series water heaters to the recirculation line. If this is the case, set any
unconnected”A”model water heaters to Internal Recirculation Mode.
●
For any NPE-A2 water heater that is connected to the recirculation line, each individual unit must
be set to the proper recirculation mode utilizing the 2-way valve and front panel DIP switches. Refer
to the NPE Installation Manual for additional details.
8.1.1 Piping Sizes and Considerations
When plumbing a cascading system, consider the following pipe diameters and flow rates. Note that flow rates
above 6.6 ft/s may cause pipe erosion. These specifications may vary depending on installation conditions.
Piping Sizes for an NFC-H Boiler with up to 15 NPE-240A2 or NPE-240S2 Water Heaters
Model
ΔT=54°F Flow rate
(GPM)
Water Velocity
(ft/s)
Pipe Diameter (mm/in)
NFC-H
NPE-240A2
or
NPE-240S2
1
1
14.38
5.61
25A
1 in.
2
21.57
5.54
30A
1
1
/
4
in.
3
28.77
5.21
40A
1
1
/
2
in.
4
35.96
6.53
40A
1
1
/
2
in.
5
43.15
4.49
50A
2 in.
6
50.34
5.24
50A
2 in.
7
57.5
6.00
50A
2 in.
8
64.72
4.39
65A
2
1
/
2
in.
9
71.92
4.75
65A
2
1
/
2
in.
10
79.11
5.34
65A
2
1
/
2
in.
11
86.30
5.84
65A
2
1
/
2
in.
12
93.49
6.33
65A
2
1
/
2
in.
13
100.68
6.79
65A
2
1
/
2
in.
14
107.87
5.11
80A
3 in.
15
115.07
5.44
80A
3 in.
Summary of Contents for NFC-250/175H
Page 67: ...67 Venting for Combustion Air WARNING The vent installation detector Detectable Undetectable...
Page 149: ...Memo...
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