U.S. Boiler Company ASPEN ASPN-085, Installation, Operating And Service Instructions, Page: 16 / 180

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VII. Venting
A. Vent System Design
There are three basic ways to vent this boiler:
• Horizontal (“Side Wall”) Twin Pipe Venting (Figure 7.0a) - Vent system exits the building through an outside wall.
Combustion air and flue gas are routed between the boiler and the terminal(s) using separate pipes for at least part of the
way. A summary of Horizontal Twin Pipe venting options is shown in Table 7.5.
•
Vertical Twin Pipe Venting (Figure 7.0b)
- Vent system exits the building through a roof. Combustion air and flue gas
are routed between the boiler and the terminal(s) using separate pipes for at least part of the way. A summary of Vertical
Twin Pipe venting options is shown in Table 7.13
• Split Venting (Figure 7.0c) - Exhaust system exits the building through a roof, and combustion air is drawn from a
terminal mounted on the side wall. A summary of split venting options is shown in Table 7.21
All of these systems are considered “direct vent” because the air for combustion is drawn directly from the outdoors into the
boiler. One of the vent option columns in Tables 7.5, 7.13, 7.21 must match the planned vent and air intake system exactly.
Design details applying to all vent systems are shown in this section. Observe all design requirements in this section, as well as
those unique to the type of system being installed:
• B - Design Requirements Unique to Horizontal Twin Pipe Vent Systems
• C - Design Requirements Unique to Vertical Twin Pipe Vent Systems
• D - Design Requirements Unique to Split Vent Systems
WARNING
Asphyxiation Hazard. Failure to vent this boiler in accordance with these instructions could cause
products of combustion to enter the building resulting in severe property damage, personal injury or
death.
Do not interchange vent systems or materials unless otherwise specified.
The use of thermal insulation covering vent pipe and fittings is prohibited.
Do not use a barometric damper, draft hood or vent damper with this boiler.
When using the CPVC/PVC vent option, the use of CPVC is required when venting in vertical or
horizontal chase ways.
Do not locate vent termination where exposed to prevailing winds. Moisture and ice may form on
surface around vent termination. To prevent deterioration, surface must be in good repair (sealed,
painted, etc.).
Do not locate air intake vent termination where chlorines, chlorofluorocarbons (CFC’s), petroleum
distillates, detergents, volatile vapors or other chemicals are present. Severe boiler corrosion and
failure will result.
The use of cellular core PVC (ASTM F891), cellular core CPVC or Radel (polyphenolsulfone) is
prohibited.
Do not locate vent termination under a deck.
Do not reduce specified diameters of vent and combustion air piping.
When installing vent pipe through chimney, as a chase, no other appliance can be vented into the
chimney.
Do not allow low spots in the vent where condensate may pool.
DANGER
Failure to follow this warning could result in a sphyxiation and/or carbon monoxide poisoning. Correct
venting material and installation is required for proper vent operation. PVC Vent Systems must include at
least 30 inches of CPVC and one CPVC elbow between the boiler and PVC vent piping. See this Section, VII.
Venting for complete information.