A rooftop NEMA-3R enclosure and variable frequency drive are supported by two 2x2x1/4 hollow structural section steel columns attached with Unistrut P1000 channels and 3/8-inch diameter machine bolts with spring nuts. Each column features a 1/4-inch welded cap plate at the top and a 3/8-inch by 8-inch by 8-inch base plate secured with a typical 3/16-inch fillet weld. The base plates are anchored to the concrete roof using four 3/8-inch diameter Hilti KB-TZ stainless steel expansion anchors with a 2-inch minimum embedment. A 1-inch non-shrink grout layer is provided beneath the base plates as required. The overall frame height is limited to 76 inches maximum with a 24-inch minimum width spacing.
ROOF NEMA-3R ENCLOSURE HSS 2x2x1/4 UNISTRUT P1000 3/8" DIA. MACHINE BOLT AND TYP. 3/16 24" MIN. 76" MAX. SPRING NUT (P1010) TYP. 1/4" WELDED CAP PLT. TYP. 3/8"x8"x8" PLT. WITH (4) 3/8" DIA. HILTI KB-TZ STAINLESS STEEL WITH 2" MIN. EMBED. 5" 1-1/2" (TYP.) 4" 4" 1" NON-SHRINK GROUT IF REQUIRED. VFD - 2 1 3
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