/ Field knowledge · IMC 803
The connector is not leftover pipe.
IMC 803: the connector is the piece that fails in the field. Size, material, slope, support, pass-through, and combustible clearance have to be one continuous system from the flue collar to the chimney or vent.
Educational 2024 IMC 803. Confirm adopted edition and appliance listing. This is not a connector design. Clearance reductions only under IMC 308.
- A connector is required unless the chimney or vent attaches directly to the appliance. Stay in the appliance room except where 803.10.4 permits otherwise. Single-wall pipe cannot be used through unheated spaces. Do not reduce below the appliance flue collar. Branch connections follow the vent manufacturer.
- Manual dampers generally prohibited except for solid-fuel chimney connectors. Automatic dampers for oil-fired heating appliances: listed to UL 17. Multiple connectors into a common vent: the smaller connector enters at the higher level.
- Vent connectors must be metal. Chimney connector thickness increases with size and heat classification (Tables 803.9(1) and 803.9(2)). Pitch upward at least 1/4 inch per foot. Connect to the inner face of the liner without projecting into the flue.
- 803.10.4: chimney connectors cannot pass through floors, ceilings, or fire-resistance-rated walls. Combustible-wall pass-throughs require a listed system or an approved Table 803.10.4 method — clearance alone is not the assembly. 803.10.6: Table 803.10.6 by appliance type and heat classification unless the listing says otherwise.
Clearance without the pass-through assembly
A 6-inch gap in the air is not Table 803.10.4. Trace collar → material → slope → support → pass-through → combustibles. If any link is missing, it comes back as a field problem instead of a comment.
Source: Daily Code Talk 803 · construction: 803.8–803.9 · dampers: 803.5–803.7 · geometry: 803.10.1–803.10.5 · pass-through: 803.10.4 · clearance: 803.10.6 · 802: listed vents · 308: clearance reduction.
What to send
Flue-collar size, connector length, and whether it goes through a wall or unheated space.
If the connector ducks through the wall with “clearance”
Send the section. MasterBuild will say whether 803.10.4 even has a listed assembly — or the pitch is flat.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
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