Weil-McLain 88 - Manual (Page 29)

"OILER
29 Part No. 550-100-068/1009
Connect breeching and venting systems
General venting information
Model 88 boilers operate with positive overfire pressure. Adjust 1.
damper assembly (see Figure 49, page 33) during burner start-up
to achieve 0.1" W.C. positive pressure at damper sample hole.
Select type of venting system
&ORCED
Boiler, breeching and stub vent operate at positive pressure. Entire s
system must be gas-tight to prevent leaks. Stub vent height must
be limited to prevent negative draft with 3-foot minimum stub
vent height above roof. See Figure 44 and Figure 46.
"ALANCED
Boiler operates with positive pressure overfire. Chimney s MAY
provide excess draft which may require a barometric draft control
installed and set to provide minimum draft to maintain 0.1" posi-
tive pressure at flue collar. Minimum chimney height above roof
is 3 feet. See Figure 45 and Figure 47.
Construct metal breeching:
See 1. Figure 43 for minimum breeching diameter.
Select material type and thickness in compliance with local 2.
codes.
Conventional flue pipe should not be used as it could
leak flue gases and carbon monoxide emissions through
seams and joints, resulting in severe personal injury or
death.
Refer to ASHRAE Guide for chimney and breeching calculations 3.
and construction and lining.
Long horizontal breechings, excessive number of tees and
elbows or other obstructions restricting combustion gas
flow can result in possibility of condensation, flue gas
leakage and carbon monoxide emissions, causing severe
personal injury or death.
Minimum breeching diameter &IGURE
Boiler
model
I=B=R
vent or liner diameter
(inches)
Boiler flue
collar
dimensions
(inches)
Forced
draft
Balanced
draft
488 10 12 10 round
588 10 15 10 round
688 12 15 10 round
788 12 18 12 round
888 14 18 12 round
988 14 18 14 round
1088 14 21 14 round
1188 16 21 14 round
1288 16 21 14 round
1388 16 24 14 round
1488 18 24 16 round
1588 18 24 16 round
1688 18 24 16 round
1788 18 24 16 56 x 19(6 oval
1888 20 27 16 56 x 19(6 oval