A tubular base plate assembly has a lower surface connected to a heating system component and an upper surface. A tubular seal plate assembly is positioned above the base plate assembly upper surface having a mating surface facing the base plate assembly upper surface with a plurality of grooves therein. Sealing material is provided within the grooves. A tubular hub assembly is positioned above the seal plate assembly. A plurality of fasteners connects the seal plate assembly to the hub. A plurality of external brackets connects the seal plate assembly to the base plate assembly to secure the seal plate assembly. The sealing material forms a first gasket between the seal plate assembly and the base plate assembly. Each of the external brackets is joined to the tubular base plate assembly, so that the external brackets and the tubular base plate assembly are integral.