lugs versus a ground bar

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
It seems a long standing practice for industrial control panel manufacturers to put a piece of copper bar in to use as a ground bar that is typically just bolted to the sheet iron.

This has gotten to be an expensive thing to do with the cost of copper being what it is these days. That and the cost of drilling and tapping the bar for the lugs and the mounting.

Other than tradition, is there any real downside to just connecting the ground wires with lugs direct to the sheet iron?

Another practice that seems common that I just don't get is the practice of running a large gage wire from the ground bar to a lug near the disconnecting means? The conductivity of the sheet iron is far less than that of the wire so what benefit is there? Again, other than tradition.
 

dicklaxt

Senior Member
You would still have to drill the sheet metal and then prep it and it would be an unsightly image ,, wrenching down on the bar is probably a more positive and permanent installation as well.

JMO

dick
 

meternerd

Senior Member
Location
Athol, ID
If we're not talking about a service entrance panel, here's my thoughts. If multiple EGC conductors are connected to the equipment, I would much rather just screw a lug onto a threaded bar than take the time to drill a hole, sand off the paint, then use a sheetmetal screw or a screw with a nut on the back to connect the grounds. As far as the big wire to a lug near the disconnect, it's probably done that way because the EGC from the source is pulled along with the phase and neutral conductors, so they will all likely be easier to terminate if they are all going to the same location. On a service panel, it's done that way so you can connect the GEC to the ground bus instead of the neutral bus (250.24.A.4). Copper prices compared to the cost of all of the other components is probably minimal. Just my humble opinion.
 

masterinbama

Senior Member
It seems a long standing practice for industrial control panel manufacturers to put a piece of copper bar in to use as a ground bar that is typically just bolted to the sheet iron.
Why not just purchase a ground bar kit like is installed in 1000's of panels everyday and have UL list it as part of your panel? $5 at the Depot.

7fff00f9-c2c8-46fc-b929-cf16dc8d6d0c_300.jpg
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Why not just purchase a ground bar kit like is installed in 1000's of panels everyday and have UL list it as part of your panel? $5 at the Depot.

View attachment 7277
They tend to stop at #4.

I actually talked to our UL engineer about this yesterday. He seemed more receptive to the AL wire idea than this.

The ironic part is that I am not sure the common copper bar used as a ground bar even meets the actual wording of the UL508a requirements as a ground bar, even though it is a very common thing to do.
 

fmtjfw

Senior Member
Where does it require copper?

Where does it require copper?

As I read it the bar must be 1/4 x 2 inch, thickness and width, and made of aluminum or copper.
 

fmtjfw

Senior Member
Sheetmetal screw?

Sheetmetal screw?

If we're not talking about a service entrance panel, here's my thoughts. If multiple EGC conductors are connected to the equipment, I would much rather just screw a lug onto a threaded bar than take the time to drill a hole, sand off the paint, then use a sheetmetal screw or a screw with a nut on the back to connect the grounds. As far as the big wire to a lug near the disconnect, it's probably done that way because the EGC from the source is pulled along with the phase and neutral conductors, so they will all likely be easier to terminate if they are all going to the same location. On a service panel, it's done that way so you can connect the GEC to the ground bus instead of the neutral bus (250.24.A.4). Copper prices compared to the cost of all of the other components is probably minimal. Just my humble opinion.
Sheetmetal screws are a no no!:rant:
 
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