Detroit Radiant Products Company UH Series - Manual (Page 30)

30
UH Series 3.0 Installation • Rooftop Venting • Horizontal Venting (Category III)
Figure 3.9 • Rooftop Venting - Side View
Horizontal Venting (Category III)
An appliance that operates with a positive vent static pressure and with a vent gas temperature that
avoids excessive condensate production in the vent is said to be ‘Category III’. The UH Series heater is
considered a Category III appliance if the venting system meets all of the following criteria:
• The vent system terminates horizontally (sideways).
• The vent terminates vertically, but the length of the horizontal portion of the vent run exceeds 75% of
the vertical rise length. (e.g.- If the vertical vent height is 10 feet, the horizontal run is greater than
7-1/2 feet).
• The vent terminates below 5 feet of the vent connection on the unit.
Seal vent pipes with high temperature sealant and three (3) #8 sheet metal screws. Vent enclosed
spaces and buildings according to the guidelines in this manual and applicable national, state,
provincial and local codes.
You may either use an agency certified Category III venting system, or single wall vent pipe with all the
seams and joints sealed with metallic tape or silicone sealant suitable for temperatures up to 400°F.
Wrap the tape two full turns around the vent pipe. For single wall vent systems, one continuous section
of double wall vent pipe may be used with the vent system to pass through a wall or barrier.
All horizontal Category III vents must be terminated with a Simpson-Duravent sidewall vent cap (P/N:
SWD-4 for 4-inch venting or P/N: DB-208 for 3-inch venting).
*Consult the NFPA ANSI Z223.1 Gas Vent Termination criteria if roof pitch exceeds 9:12.
Vent Cap
Double-Wall B-Vent Pipe
Firestop Spacer
B to C Adapter
Roof
24 in. Min.*
Heater
Clean Out Tee Fitting
Clean Out Cap