CT80-250
Natural Draft - Installation & Operation Instructions
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Odyssey
15
6.0 NATURAL DRAFT APPLICATIONS
Natural Draft Rules and Guidelines
1.
Acceptable Venting Material - Use vent material approved by National Standards NFPA 31 (USA) or CSA
B139 (Canada) and local codes.
2.
Venting Application - Venting must be connected to a chimney for models operating with Natural Draft.
3.
Chimney Condition - Inspect existing chimney before installing new boiler. Deterioration of mortar joints
should be repaired prior to using.
4.
Chimney Height - Chimney must extend 3’ above the highest point where it exits the roof and 2’ higher than
any part of the structure within 10’.
5.
Cleaning - Clean chimney, if required; ensure it is clear of any blockages before connecting breeching.
6.
Liner Condition - Damaged liner or pipe should be repaired before commencing installation.
7.
Minimum Clearances - Observe clearances to combustibles illustrated in Figure 3-1 and Table 3-1:
8.
a) Double-wall vent (Type-L) 6
"
9.
b) Single-wall vent
9
"
10.
Chimney Sizes - Minimum chimney sizes should be used. See Table 6-1.
11.
Combustion Air - An adequate supply of combustion air must be available to ensure proper combustion.
12.
Interlock - If a damper is used to provide make-up air for combustion, it must be interlocked with the burner
to prevent the burner starting before the damper is opened.
Potential Condensation - Oversized chimneys, outside masonry chimneys, and/or de-
rated inputs can result in flue gases condensing in the chimney.
Combustion Air
Natural Draft boilers require an adequate amount of combustion air to sustain proper combustion and prevent
flue gas leakage. The appliance’s air-inlet draws combustion air from Indoors or Outdoors depending on whether
there is a sufficient natural infiltration (air changes) occurring to sustain combustion. If the building is newer and
relatively air tight, outdoor air should be considered. For recommended practice, refer to NFPA 31 (USA) or
CSA B139 (Canada).
Air Circulation - The boiler shall be located so as not to interfere with proper circulation
of combustion, ventilation, and dilution air.
Make-up Air - The operation of exhaust fans, kitchen ventilation systems, clothes dryers,
and fireplaces must be considered in determining the adequacy of a space to provide
combustion air requirements. Failure to ensure adequate make-up air to all appliances may result in flue gas
leakage, personal injury or death.
Permanent Openings for Combustion Air
The appliance space or boiler area requires a permanent opening(s) capable of providing adequate combustion air
to the boiler. If using two permanent openings, one opening must be within 12 inches of the ceiling, the other
within 12 inches of the floor. The minimum dimension of air openings to the appliance space shall not be less
than 3 inches in any one direction, including rectangular ducts. Round ducts are connected to the permanent air
openings, duct sizes must have a minimum cross-sectional area of 3 inches. See “Sizing Combustion Air
Openings” for more details.
The minimum size of permanent openings and how combustion air is supplied to them depends on three factors:
1.
What is the input capacity of the boiler in Btu/hr?
2.
How is the Combustion Air being supplied?
3.
Is make-up air required for other appliance in the room competing for the same air?
