Weil-McLain 88 manual Connect breeching and venting systems, General venting information

Boiler manual: • Installation • Start-Up • Maintenance • Parts

Connect breeching and venting systems

General venting information

1.Model 88 boilers operate with positive overfire pressure. Adjust 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

Forced draft

•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.

Balanced draft

•Boiler operates with positive pressure overfire. Chimney 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:

1.See Figure 43 for minimum breeching diameter.

2.Select material type and thickness in compliance with local 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.

3.Refer to ASHRAE Guide for chimney and breeching calculations 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.

Figure 43 Minimum breeching diameter

Boiler	I=B=R		Boiler flue
model	vent or liner diameter		collar
	(inches)		dimensions
			(inches)
	Forced	Balanced
	draft	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

Part No. 550-100-068/0308 29