Navien NFC-250/175H, Руководство по установке, Страница: 92 / 151

92 Installing a Common Vent System
Common Vent Length Table
[Total Length (L) = W + H]
Vent Lengths for an NFC-H Boiler with up to
7 NPE Water Heaters
The following table provides information on the
required load amount and the total length for
one NFC-H boiler with up to 7 NPE water heaters
installed.
Required
Load
(Total
BTU/H)
Model Total Length (ft)
NFC-
250/200H
NPE-240 D=3” D=4” D=6” D=8”
409,900
1
1 60 106 200
609,800 2 40 71 160
809,700 3 30 53 120
1,009,600 4 96 150
1,209,500 5 80 142
1,409,400 6 68 121
1,609,300 7 60 106
Note
●
Every 90° elbow used is equivalent to
8 linear feet (2.4 m) of vent length.
●
Branch pipe lengths are not added
to the allowable equivable vent
lengths that are provided in the
following charts.
9.1.2 Determining the Length of a
Common Vent System
Follow the instructions listed below to determine
the length of a common vent.
1. Add the BTU/H input ratings for each unit in the
cascading system to determine the total BTU/H
rating.
2. Determine the total length (L) of the common
vent, which consists of the horizontal width (W)
and the vertical height (H): Total length (L) = W
+ H.
Exhaust
D
W
H
Intake
Siphon loop
Drain hose
End cap
Drain