Smith Cast Iron Boilers GS110W - Manual (Page 7)

GS110 DIRECT VENT BOILER INSTALLATION AND OPERATION INSTRUCTIONS Page 7
Figure 6 - Vertical Positive Pressure Venting with Outdoor Combustion Air (Cat. III)
All joints in metal intake air systems must be secured
using corrosion resistant fasteners and sealed using a
suitable Silicone caulk. If PVC or CPVC is used, the
joints must be cleaned with a suitable solvent and
connected using a solvent based PVC cement. The
intake air system MUST be supported by the building
structure not the boiler/water heater.
Intake Air Option - Vertical Guidelines
A listed, nonrestrictive intake air cap must be used. The
intake air cap must terminate as shown in Figure 6. The
penetration point in the roof must be properly flashed
and sealed.
Intake Air Optional - Horizontal Guidelines
The maximum equivalent length for the horizontal intake
air pipe is listed in Table 2. The intake air system must
be pitched down, toward the terminal, 1/4" per foot
(21 mm per meter).
If horizontal runs exceed 5 feet (1.5 m) they must be
supported at 3 foot (0.98 m) intervals with overhead
hangers. Figures 7 through 10 show the four horizontal
air intake options. The intake terminations certified for
use the GS110 are listed in Table 5.