Electrical Box Punch Out Sizes

Electrical trade sizes and plumbing trade sizes are equal and are based on pipe sizes.

Electrical box punch out sizes.

In the electrical panel above the inner 3 4 knockout was the easiest to punch out first. First determine the size of the missing knockout hole and subtract 3 8 to figure out what size knockout plug you ll need. Codes also limit the number of wires that can enter an electrical box or electrical receptacle depending on the inside volume of the box and the gauge of the wires. Bx cutters after cutting out some concentric knockouts.

The outlet addition methods we show here are based on the most common wiring 14 gauge wire on a 15 amp circuit and an 18 cu in. An example is 1 2 inch 1 3 cm trade size. If you punch out too big of a hole you can use reducing washers. The 3 4 inch 1 9 cm trade size is a 1 1 8 inch 2 9 cm opening.

A pilot hole is drilled into the box as needed then a draw bolt and die are inserted into the hole and a punch is threaded onto the draw bolt. The national electrical code article 314 contains complete details and tables of electrical box sizes in dimensions and cubic inches and should be consulted for complete accuracy because the actual size of the box required in cubic inches depends on the number of wires that will be within that enclosure. Temco th0390 manual knockout punch driver kit set for inch to 2 inch electrical conduit hole sizes 1 2 2 conduit size 4 7 out of 5 stars 56 84 95 84. Different electrical box sizes fit varying installation needs.

A standard rectangular shape is the most common electrical box. To determine the actual opening for this size you need to add 3 8ths of an inch which is 7 8ths of an inch opening. Box typical inside dimensions are about 2 in. Notes to the table above.

Standard piece makertm punch and conduit size actual punched hole diameter in 1560. It houses a single electrical switch or outlet and comes in metal or nonmetallic units. A screw type or manual knockout punch is tightened with a wrench to knock out the hole. First knockout punched inward for removal.

The shape of an electrical box can help you identify its purpose. If you punch out the wrong hole you can fill it with a knockout seal.