VST VRP-150 - Determining the Length of Common Vent System

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Installation Manual
Determining the Length of Common Vent System
When selecting an installation location, you must ensure that clearances will be met and the vent length will be within required limits.
Requirements
• Intake and exhaust terminations must vent outside the building.
Add the BTU/H input ratings for each unit in the common vent system to determine the total BTU/H rating.
Exhaust gas
Intake air
Drain
Vent Length for VRP/VRS Water Heater
Qty
Required Load
(BTU/H)
Total Length (ft)
D=3" D=4" D=6" D=8"
Min Max Min Max Min Max Min Max
2
398,000 13.1 43 13.1 70
3
597,000 20 28 20 50 20 112
4
796,000 20 21 20 38 20 84
5
995,000 21.7 67 21.7 120
6
1,194,000 21.7 56 21.7 100
7
1,393,000 23.5 48 23.5 85
8
1,592,000 25.2 42 25.2 75
Notice
• Every 90° elbow used is equivalent to 8 linear feet (2.4 m) of vent length.