Weil-McLain 80 Connect breeching and venting systems, General venting information, Forced draft

• Installation • Start-Up • Maintenance • Parts

13 Connect breeching and venting systems

General venting information		Construct metal breeching:
• Model 80 boilers operate with positive overfire pressure. Adjust		• See Table 14 or Table 15 for minimum breeching diameter.
damper assembly (see page 33) during burner start-up to achieve		• Select material type and thickness in compliance with local codes.
0.1" W.C. positive pressure at damper sample hole.
				Conventional flue pipe should not be used as it could
Select type of venting system				leak flue gases and carbon monoxide emissions
				through seams and joints, resulting in severe
Forced draft				personal injury or death.
Boiler, breeching and stub vent operate at positive pressure. Entire		• Refer to ASHRAE Guide for chimney and breeching calculations
system must be gas-tight to prevent leaks. Stub vent height must be		and construction and lining.
limited to prevent negative draft with 3-foot minimum stub vent				Long horizontal breechings, excessive number of
height above roof. See Figures 31 and 32.
				tees and elbows or other obstructions restricting
Balanced draft				combustion gas flow can result in possibility of
Boiler operates with positive pressure overfire. Chimney may provide				condensation,flue gas leakage and carbon monoxide
				emissions, causing severe personal injury or death.
excess draft which may require a barometric draft control installed
and set to provide minimum draft to maintain 0.1" positive pressure
at flue collar. Minimum chimney height above roof is 3 feet. See
Figures 33 and 34.
			Table 14 Minimum breeching diameter —
					forced draft venting
Figure 31	Figure 32

Stub vent – forced draft — single boiler

Stub vent – forced draft — multiple boilers

Figure 33

Conventional chimney – balanced draft with barometric draft control when required — single boiler

Part No. 550-141-935/0602

Figure 34

Conventional chimney – balanced draft with barometric draft control when required — multiple boilers

Table 15 Minimum breeching diameter — balanced draft venting

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