Nesco makes knockout closures, the steel plugs used to seal unused knockout holes in panels, boxes and enclosures. The KO50 listed here is a 1/2-inch steel closure sold in packs of 100 for about $19. Sealing unused openings is a code requirement, not a finishing preference: an open knockout leaves live parts accessible and defeats the enclosure rating. Steel closures suit steel enclosures and hold better than plastic under vibration or heat. Buying by the 100-pack is the sensible approach for anyone doing panel work regularly, since these are consumed a few at a time on every job.
**Why do unused knockouts have to be filled?**
An open knockout leaves energised parts accessible and defeats the enclosure's protection rating. The Canadian Electrical Code requires unused openings to be effectively closed. It is one of the most common items written up on an inspection.
**What size closure do I need?**
Match the trade size of the knockout, not the measured hole. The KO50 is for 1/2-inch knockouts. Standard trade sizes step 1/2, 3/4, 1, 1-1/4 inch and up, and each needs its matching closure.
**Steel or plastic closures?**
Steel is preferred for steel enclosures and holds up better under vibration and heat. Plastic closures are lighter duty. Where the enclosure has a specific environmental rating, use a closure listed to maintain it.
**How are these packaged?**
The KO50 comes in packs of 100. That is the practical quantity for a contractor, since a few get used on every panel and box installation and they are easy to run short of on site.
**Do you carry other sizes and other Nesco items?**
Ask us. Call (905) 553-7171 or email sales@mapleelectricsupply.ca with the size and quantity and we will confirm what we can supply and at what price.