Hubbell 1040 Two-piece Knockout Seal 3.5 Inches

Product Description

The HUBBELL 1040 is a two-piece knockout seal designed to close unused knockout openings in electrical enclosures, junction boxes, and panels. It provides a secure, finished closure that helps maintain the integrity of the enclosure and supports compliance with electrical code requirements for sealing unused openings. The two-piece design allows installation without access to the back of the panel, making it practical for field use. This seal fits a 3.5-inch knockout opening and is typically installed by licensed electricians during new construction, service work, or panel upgrades.

This knockout seal is used in commercial and residential electrical installations wherever an unused knockout must be closed. Common applications include load centers, junction boxes, pull boxes, and other metallic or non-metallic electrical enclosures. The two-piece snap-together construction is suited for situations where a standard one-piece seal cannot be inserted from the front of the enclosure alone.

Key Features

• Two-piece construction allows front-only installation without rear access
• Fits 3.5-inch knockout openings in standard electrical enclosures
• Provides a clean, finished closure for unused panel openings
• Supports NEC requirements for sealing unused knockout openings
• Compact design for use in tight or crowded enclosure environments

Compatibility

Designed as an OEM-style replacement seal for standard 3.5-inch knockout openings found in residential and commercial electrical enclosures, junction boxes, and load centers.

Installation Notes

Installation is typically performed by a licensed electrician. De-energize and lock out the panel or enclosure before beginning work, in accordance with NFPA 70E safe work practices. The two-piece seal is inserted through the knockout opening and snapped together to secure it in place. Verify the installed seal sits flush and does not protrude in a way that could interfere with conductors or other components inside the enclosure.

Technical Specifications

• Knockout Opening Size: 3.5 inches
• Design: Two-piece

Standard Information

• Brand: HUBBELL
• Manufacturer Part Number: 1040