Hi, I have an old Murray LC012, it has no grounding bar and all copper ground wires are going into a lug on the outer side of the load center. Now I need to add 4 more lines and I have no space in that lug. So I assume I need to add a ground bar kit. So far so good. But there is one thing I don‘t understand. The bar is mounted to enclosure using a couple of screws. Assuming the enclosure is grounded, do I need any additional wire run from the grounding lug on the outside wall of the enclosure to the new grounding bar, or those screws provide adequate connection? Thanks a lot in advance!!!
The screws provide the connection. The bar is bonded to the enclosure and the lug you mention is also bonded to the enclosure. You should verify that the lug is bonded very well to the enclosure. However if you want to you can run a bonding wire between them. Does this panel have drilled and tapped holes for the ground bar? If not you will have to drill and tap the enclosure to install the bar. No matter if their are tapped holes available or not you should also make sure that the holes are free of debris and paint or anything that could possibly insulate the bar from the enclosure. You want the lowest impedance possible at these connections. When doing this be sure to turn off the main breaker and be very aware that the terminals ahead of the breaker are still hot. If you are the least bit unsure about this please hire a licensed electrician to perform this for you. Key word here is licensed, not some fly by night guy. Hope this helps. In addition to Stephens comment: Look on the ground bar kit instructions. You may find that the ground bar is listed to accept more than one wire under one screw when used for grounding purposes. However if you don't find this listing do not put more than one wire under one screw.
When you install your ground bar remove all the wires going to the ground lug and place them on the grounding bar. It is against the NEC code to have more than one wire on a grounding lug. The screws holding the ground bar on will bond the bar with the box.
