Detroit Radiant Products Company LD3 Series - Manual (Page 29)

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LD3 Series 3.0 Installation • Common Venting (Category I) • Common Rooftop Venting
Common Venting (Category I)
The common vent system and all attached appliances must be Category I.
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 11.2 and 11.3 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 3.19 • Common Rooftop Venting - Side View
**Consult the NFPA ANSI Z223.1 Gas Vent Termination criteria if roof pitch exceeds 9:12.
Rooftop Vent Cap
Roof
Dual Exhaust Assembly
Heater
Firestop Spacer
Double-Wall B-Vent
24 in.
Min.**
Heater
3” Single-Wall Vent Pipe
4” Single-Wall
Vent Pipe