156 NPE Service Manual
9.6 Common Venting
Model : NPE-150S, 180A, 180S, 210A, 210S, 240A, 240S
When cascading the water heaters with other Navien water
heaters, you can install a common venting system. Do not use
common venting if the water heater is used in a cascading system
with other manufacturer’s water heaters. Include a condensate
drain in the main trunk as illustrated in the following examples.
●
Venting the Exhaust Only (Non-Direct)
Exhaust
Condensate
Drain
Intake
Cap
H
W
D
●
Venting Intake and Exhaust to the Same Location
Exhaust
Condensate
Drain
Intake
Cap
36" (900mm) min.
12" (300mm) min.
12" (300mm) min.
●
Venting Intake and Exhaust to Dierent Locations
Exhaust
Condensate
Drain
Intake
Cap
To determine the size of a common vent:
1. Add the BTU/H input ratings for each water heater 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
Condensate
Drain
Intake
Cap
H
W
D
3. Refer to the common vent table that follows to determine the
minimum length required for the common vent, based on the
total BTU/H rating, and the diameter of the vent pipe.
NOTE
For each short radius elbow that will be used in the vent, add 8
feet (2.4 m) to the total length. For each long radius elbow that
will be used in the vent, add 5 feet (1.5m) to the total length.
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