Bock Water heaters OT300-A Installation And Operation Instruction Manual page 22

SECTION IV: INSTALLATION (cont.)
VENT & COMBUSTION AIR INTAKE (cont.)
Vertical Venting, Direct Vent 2-pipe termination
This water heater may be vented vertically (through a roof) with a two-pipe termination. Two
holes through the roof are required for the vent and combustion air intake pipes. All
clearances must comply with local codes or the latest edition of NFPA 54/ANSI Z223.1 or CSA
B149. As a basic guide, the following minimum clearances shall be used:
• Minimum 12 inches (30 cm) above roof.
• Minimum 12 inches (30 cm) above anticipated snow level.
• Maximum 24 inches (61 cm) above roof level without additional support for vent.
• 4 feet (1.2 m) from any gable, dormer or other roof structure with building interior access
(e.g. vent or window).
• 10 feet (3 m) from any forced air inlet to the building. Any fresh or make-up air inlet such as
a dryer or furnace area is considered to be a forced air inlet.
• Minimum 24 inches (61 cm) between the vent and combustion air intake terminal
centerlines.
Install piping through the roof as shown in Figure 13. Adequate length of pipe must protrude
beyond the exterior of the roof (see dimension Y). Directions for cementing joints (such as the
terminal fittings to the straight pipe) can be found on page 25. Two 90 elbows are
recommended for the intake and exhaust terminations to reduce the risk of rain, snow, or
foreign objects entering the system. Install a screen inside the air intake termination fitting.
Complete the installation of the remainder of the vent and air intake system and attach to the
water heater. Piping must be sufficiently supported. At minimum, it is recommended that a
support is placed along the vent or air intake piping every 4 feet.
Page 22
Figure 13: Vertical Venting, 2-pipe termination
Never install air intake terminal above vent (exhaust) terminal.
!
CAUTION