Detroit Radiant Products Company UH Series - Manual (Page 32)

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UH 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 3.11 • Common Rooftop Venting - Side View
Rooftop Vent Cap
Roof
Dual Exhaust Assembly
Heater
Firestop Spacer
Double-Wall B-Vent
24 in.
Min.*
Heater
*Consult the NFPA ANSI Z223.1 Gas Vent Termination criteria if roof pitch exceeds 9:12.