View Full Version : Green Bonding Screw ??

June 3rd, 2004, 06:07 PM
In the main service panel, if the neutral and ground wires are attached to the same buss bar, is the green bonding screw that comes with a new panel supposed to be installed in the box?

June 3rd, 2004, 06:32 PM
If this is a main service panel then yes the bonding jumper/screw must be installed. The neutral and ground must be bonded together.

If it is a subpanel then it must not be installed.


June 8th, 2004, 04:57 PM
Where *exactly* should this screw be installed? (I am trying to finish someone else's work and both the instructions for the panel and the green screw are missing.)

Can I buy a screw like this to put in? My inspector has told me that's the only thing preventing me from passing my permanent electric inspection. He indicated that the screw should be somewhere above the right bus bar, while the grounding wire could go into the left bus bar. This seems reversed to me. Does it really matter?


June 8th, 2004, 05:23 PM
The screw is usually in the neutral bus. You tighten it down to make contact with the metal cabinet, which is then in contact with the ground bus.

I would assume that your Home Depot, or Lowes or whatever you have where you live could sell you this screw. Is this a new panel? If so, the screw should have came with it. Maybe in a plastic parts bag, but usually it is already installed in the neutral bus, and you need to simply screw it down to make contact with the panel.

What brand of panel is it?

June 8th, 2004, 05:35 PM
It is typically more than just a "green screw". Usually it is a metal strip that will fit into one of the neutral bus lugs and then the screw is used to bond it to the backplate of the load center.


June 8th, 2004, 06:54 PM
The pic that Homer posed is typical of panels such as Cutler-Hammer. If your panel is a Square D, you have just a green screw. Unfortuneately, this screw has a dog-gone weird thread. I think it's 12-28. The screw must also be green. If you lived near me, I'd give you one. I save then from sub panel installs where I don't need the bonding screw. Maybe you could swing by a local electrician, and they'd give you one? Surely I'm not the only one who saves these. I feel your pain.

June 8th, 2004, 08:24 PM
Thanks for all of the very helpful advice!! I am almost sure that it's a Square D panel. We have definitely lost the screw. I just read on Square D's site:
"Refer to the Wiring Diagram of the device, located on the interior sidewall of the enclosure. The Wiring Diagram will state ``Box bonding when required`` and indicate the location on the neutral assembly to insert the green bonding screw. The green bonding screw, which is a self-tapping screw, will be supplied with load centers that are marked as suitable for use as service equipment."

I am planning to go out to our land tomorrow to take a look at the box and read this 'wiring diagram.' Hopefully, all I will have to do is find this special green screw and this whole phase will be complete. I will try our local electrical supply co. I think they must have something that will work for me!

Thanks again! I may post again after looking at that diagram tomorrow.

June 8th, 2004, 09:39 PM
AND... if they don't have one in stock, ask some of the guys that are waiting to be served at the counter if they have one on their truck!

June 11th, 2004, 09:43 PM
Okay (sigh.) I have confirmed that we have a Square D - Homeline 200 amp panel. I called Square D to get the part number for the "missing screw." They did not seem 100% sure, but gave me part # 40283-458-50, said they could not supply it to me, I would have to get it from my local supply company. No one had it, although one place has an almost identical part # ending in 448-50 and said the only difference was that this screw came with a torque card.

I think that I know where to put the screw, but the problem is the screw is just a normal 1-1/2" green bonding screw - not self-tapping - nor self-threading. Does this seem correct? I am going out tomorrow to try this. The board is mounted on a plywood board. Is the screw supposed to go through the back of the box? How will this work?

Thanks a lot,

June 11th, 2004, 10:05 PM
The screw should fit fine. Make sure it's screwed in until it can't move. Note: Over tighting can strip the screw, so do not over tighten, but make sure it's tight. It you do strip the screw out, then use a the metal bonding strap that Homer posted--while leaving the green screw in place. (Both need to be in place--if the green bonding screw is stripped-out).

June 11th, 2004, 11:07 PM
I paged through the Square D Digest, and noticed that the 40283-458-50 screw is the same neutral bonding screw that's used in nearly every 100-200 amp QO and Homeline panel. I can't believe that nobody has one. I've got a old peanut can on my service truck that must have 2 or 3 dozen Square D bonding screws in it, among others. The screw is "somewhat" self-tapping. The first 3 or 4 threads are tapered. The hole in the back of the panel that the screw threads into has no factory cut threads. You have to muscle the screw into the swage punched hole.

June 12th, 2004, 11:53 AM
Today, I went out to my construction site. I really think they gave me the wrong screw. Here are my two issues:

1) The hole that the wiring diagram indicates to put the screw into is just that - a hole that goes through the back of the box. We have plywood mounted under the panel, and I can see the plywood through the panel. My screw is so long that it would have to actually be screwed into the plywood. Does this even seem like the correct hole? Here is a picture of where they tell me to put the screw. It's the little hole to the left of where I wrote "this is it." (Please ignore all of the red numbers - this was the only pic I could find online.)

2) On my screw, only the very bottom thread is slightly tapered. Putting it in this hole is like sticking the screw into an empty hole. I can put it in and then pull it right back up. Unless I actually drill my plywood board and screw it in, it will not stay. I have tried, but cannot get it to catch on anything.

Am I completely on the wrong track? I just don't see why I am having such trouble inserting a screw! I'm sorry for exhausting this rather exhaustive topic. Thanks in advance for any help.

June 12th, 2004, 12:24 PM
That is, in fact, the correct hole. Maybe you do have the wrong screw? Sometimes, they do poke out the back a tiny bit (3 or 4 threads perhaps). I almost always insert the bonding screw before the panel is mounted, so I can't say if installing the screw in a mounted panel would present trouble. Could you loosen the panel mounting screws a turn or two off the plywood, and jam a screwdriver in behind the panel to shim it out a little, and then try to install the screw? I do know that you have to push rather hard on the bonding screws to get them to start in the hole. If the screw goes in okay, then just screw the panel back to the plywood tightly again.

June 13th, 2004, 10:05 PM
Well, I guess all it needed was a MAN's touch! My husband was able to muscle it in as you suggested - I think the main problem that I was having was just that I'm not strong enough to sink it into the plywood that it's mounted on. :o

In any case, it's now in, and I can finally call for my permanent inspection tomorrow. Thanks so much MDSHUNK and all others that offered help!