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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 5 at
right. 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.
When installing a single boiler, connect the flue
pipe with the same size as the boiler outlet to the
chimney, sloping upward continuously toward the
chimney approximately ¼" 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 6 - TYpiCAL VENTiNG OF 2 OR mORE UNiTS
VENTING SYSTEM INSPECTION & INSTALLATION
11
CHimNEY OR VENT SiZES
DiA. OF
CHimNEY
mODEL NO.
OpENiNG
(BREECHiNG)
SFM6225W
8
SFM7275W
9
SFM24150W
9
SFM25175W
9
SFM25200W
9
SFM26225W
9
SFM27275W
10
SFM36225W
12
SFM37275W
14
SFM47275W
14
SFM57275W
18
SFM67275W
18
SFM77275W
22
SFM87275W
22
CHimNEY
FLUE
SiZE
OUTLET
(iN. X iN. X
SiZE
FT.)
8X8X15
8"
8X12X15
8"
8X12X15
6"
8X12X20
7"
8X12X20
7"
8X12X20
8"
12X16X15
8"
12X16X15
8"
12X16X20
8"
12X16X15
8"
16X20X20
8"
20X20X15
8"
20X24X15
8"
20X24X20
8"
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