Grounding Metal Boxes

Here are some electrical tip for home outlets use a plug in circuit analyzer to check to make sure your outlets are grounded and wired correctly.

Grounding metal boxes.

On 2017 06 25 by mod re. Metal electrical boxes such as junction boxes metal gang boxes or metal receptacle light or ceiling fan mounting boxes all need to be connected to the system ground and of course all 120v and 220v circuit wire electrical splices must be made inside of a properly sized and rated box. In this way the metal raceway acts in place of the grounding wire that is found in nm cable this is also the main reason why only metal boxes may be used with metal conduit. After that you need to ground the devices.

The equipment grounding wires then connect to the screw making the metal box part of the grounding system. Grounding with conduit. All metal boxes conduit etc used in an electrical system needs to be grounded. You need to ground the box first and foremost.

The box could overheat and start a fire or someone could get a shock from touching it. How to ground in metal boxes in a system with metal boxes the pigtail method is considered the most secure. Ground wires are spliced together and attached with a pigtail to the box and receptacle. Consider the installation of an equipment grounding conductor of the wire type as a supplement to a conduit only equipment grounding conductor for especially sensitive equipment.

But you still would have to connect any grounding means from a light fixture receptacle etc to the back of the metal box via the pre drilled and tapped hole that is provided. In this arrangement both the receptacle and metal box are grounded. Metal receptacle outlet boxes must be grounded and one method is to pigtail the ground wire so that it is attached to the outlet and the metal outlet box using a green grounding screw. Most receptacles do need a ground tail.

How you ground them is where it gets interesting. As long as all the ground wires in the box are attached together and to the box. Don t rely on metal sheathing or an exposed ground wire. If a metal box is being used best practice is to insert a green grounding screw into the threaded hole in the back of the box or enclosure.

Equipment grounding conductor bond all metal enclosures raceways boxes and equipment grounding conductors into one electrically continuous system. Metal boxes need to be connected to ground ground wire connectors for wire to wire wire to box. Connecting the ground wire to a metal electrical box will energize the box in the event of a short circuit. Lets make this real simple.

You can hit the box at one grounding screw then hit the devices from the other grounding screw. In this video i show how a metal box is correctly grounded back to the main panel.