Boiler manual: • Installation • Start-Up • Maintenance • Parts
29Part No. 550-100-068/0308
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
Boiler, breeching and stub vent operate at positive pressure. Entire •
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.
Boiler operates with positive pressure overfire. Chimney •
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 ue 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 ue pipe should not be used as it could
leak ue 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
ow can result in possibility of condensation, ue gas
leakage and carbon monoxide emissions, causing severe
personal injury or death.
Minimum breeching diameter
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
16Z\, x 19M\, oval
1888
20 27
16Z\, x 19M\, oval
