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DX3L
Series
Common Venting (Category III)
• A staggered arrangement or a dual exhaust assembly (P/N: Y) must be used when joining two
heaters to a common vent so that by-products of one heater do not flow into the adjoining vent of the
other heater.
• A Category III appliance may be common vented only if the appliances are on the same control
device so that they may only be operated at the same time to prevent the backflow of exhaust gases
into a non-operational appliance. The venting system must follow all guidelines for Category III
venting as listed on pages 28-29.
• The vent connector should be routed in the most direct route from the units to the common vent.
• Where two or more vent connectors enter a common gas vent or chimney flue, the smaller
connector shall enter at the highest level consistent with the available head room or clearance to
combustible material.
• Restrictions within the common vent such as elbows should be minimized. Each elbow installed
within the common portion of the vent carrying system reduces the maximum common vent capacity
by 10%. Refer to NFPA 54 IFEC tables 13.2(a) through 13.2(e) for capacity.
• The vent connector capacities allow for the use of two 90° directional changes. For each additional
required elbow, the vent connector capacity is reduced by 10%.
• The common vent cross sectional area must be equal to or greater than the largest vent connector
cross sectional area.
Figure 3.24
•
Common Sidewall Venting - Top View
Sidewall Vent Cap
Wall Thimble
Double-Wall B Vent
Single Wall Vent
Sidewall
B to C
6 in.
Adapter
Min.
3.0
Installation
35
•
Combustion Air Requirements
Heater
Dual Exhaust Assembly
Heater
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