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VENTING SYSTEM INSPECTION & INSTALLATION
WARNING:
BOILER IS TO BE VENTED BY NATURAL DRAFT AND
SHALL NOT BE CONNECTED INTO A MECHANICAL DRAFT SYSTEM OPERATING
UNDER A POSITIVE PRESSURE.
INSPECT CHIMNEY to make certain it is constructed according to the lastest revision
of NFPA 21, when in the U.S., or the National Building Code or CSA-A405, when in Canada.
Local codes may differ from this code and should be checked. Where there is a conflict, the
local code will prevail.
This boiler must be installed into a chimney which has a tile lined masonry or metallic
chimney liner.
An unlined chimney will have leaks that will cause poor chimney performance (
NO
DRAFT
), and could result in poor positive pressure in the combustion chamber.
Horizontal portions of the venting system should not exceed 10 feet in length. Horizontal
lengths over 10 feet will have a negative effect on the chimney performance.
The chimney should extend at least 2 feet above any portion of the building within 10
feet. See figure 12 below. It should produce a negative draft of .06 to .08 inches of water
column, (W.C.), as measured with a draft gauge between the boiler and barometric draft
control while maintaining an .02 inch W.C. negative draft in the combustion chamber. See
chart below for recommended chimney or vent sizes.
Inadequate draft will cause improper combustion, resulting in dirty flue ways and high
fuel bills.
CONNECT FLUE PIPE same size as boiler outlet to chimney, sloping upward continu-
ously toward the chimney approximately 1/4" per foot. Bolt or screw joints together to avoid
sag.
If an oil fired water heater is vented into the same flue as the boiler, provide a separate
hole into the chimney whenever possible. When this isn’t possible, use a “Y” connection in
the flue pipe, using a separate draft regulator for each unit. When a chimney will not provide
adequate draft to handle the input from the water heater and boiler simultaneously, wire the
units so that only one will operate at a time, favoring the water heater.
FIGURE 12
CHIMNEY OR VENT SIZES
ROUND
SQUARE
HEIGHT
MODEL NO.
INCHES
INCHES
FEET
MIN MAX MIN MAX MIN MAX
OBC4
6
8
8x8 8x10
15
40
OBC3
6
8
8x8
8x10
15
40
