Need Help with Vent Connector Sizing

[Neal Lewis]

A 320,000 BTU input steam boiler has two 7 inch connectors attached to the draft hood. They are connected to a seven inch vent connector and run into the chimney. Is this size adequate? I have a hard time reading the AGA vent charts. There was no scorching, backdrafting, etc. Thanks

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[Bill Kibbel]

I think the referenced chart applies to vents, not vent connectors.

G2427.10.3.2 (503.10.3.2) Multiple draft hood.

For a single appliance having more than one draft hood outlet or flue collar, the manifold shall be constructed according to the instructions of the appliance manufacturer. Where there are no instructions, the manifold shall be designed and constructed in accordance with approved engineering practices. As an alternate method, the effective area of the manifold shall equal the combined area of the flue collars or draft hood outlets and the vent connectors shall have a minimum 1-foot rise.