[hidden1]

Im trying to see just where my box is grounded and bonded at .I cut power and did ohms test to panel from neutral bar and got good reading.Also noticed 2 large bolts in bottom and top of box that go outside.Are these bonding or grounding the box?

I never found a green bonding screw anywhere but there is a silver #6 going to neutral bar from copper pipe and outside box has wire to ground(isnt copper though)

 

[kbsparky]

Here is where it should be:

 

[hidden1]

without that bonding screw will i still get clear reading -ohms- from neutral to edge of box?

 

[Stubbie]

without that bonding screw will i still get clear reading -ohms- from neutral to edge of box?

I don't know what you mean " clear reading ohms ". If you probe the neutral bar and the panel metal where it is clear of paint you should get zero ohms or close to it. If you get open or high ohms the the box is not bonded.

 

[AllanJ]

I don't know what you mean " clear reading ohms ". If you probe the neutral bar and the panel metal where
it is clear of paint you should close to it. If you get open or high ohms the the box is not bonded.

Normally the green screw is used to bond the neutral bus bar (terminal strip) to the panel but we cannot
rule out an incorrect neutral to ground interconnection (bonding) somewhere else in the system or a ground
fault elsewhere in the system. If you undo the green bonding screw in the neutral bus and then get near
infinite resistance between neutral bus and panel frame, then re--insert the green screw and get zero
resistance between neutral bus and panel frame then the screw is accomplishing its job. Any sentences
beginning with "otherwise" you put after this are not proven true or false by the preceding ohmmeter tests
e.g. "the converse is not necessarily true."

In some cases a fat wire or a metal bar (bonding jumper) is connected between the neutral bus and a
ground bus in the panel and this accomplishes the same purpose as the green screw. If it's a fat wire
it should be of a size at least that of the largest other ground wire (equipment grounding conductor)
attached to that ground bus.

If neutrals are attached to more than one bus then that procedure must be approved for that model of
panel and those busses must be interconnected (bonded) with an approved bonding jumper for that panel,
not necessarily "just a fat wire." In the picture above, multiple busses attached to the same metal subframe
are properly bonded (to each other). The green screw adds the bond to the panel when needed.

 

[hidden1]

I did get zero ohms from panel to neutral bar.Dont see green screw though..
Is the metal bar you spoke on pretty easy to see?

 

[k_buz]

With the grounds and neutrals going to the same bar in the panel, you will usually get continuity between the neutral bar and the case of the panel. There are a number of reasons for this, but it [the panel] does not appear to be properly bonded.

 

[hidden1]

were the older panels, that were square d, made with screws that were not green in the late 70's as this is a older model

 

[J. V.]

Here is where it should be:

No. Look up and to the right. There is the hole.

 

[hidden1]

So all i need to do then is place the bonding screw in that hole ,attatching against box?
Had one other question: which ground clamp-for bare wire- would i need to use where the #4 solid silver wire coming from neutral attaches to copper pipe-the silver or the copper alloy one?
-still cant figure out why im getting 0 ohms to the outside of box/neutral...its a 1976 square d box

 

[kbsparky]

So all i need to do then is place the bonding screw in that hole ,attatching against box?
Had one other question: which ground clamp-for bare wire- would i need to use where the #4 solid silver wire coming from neutral attaches to copper pipe-the silver or the copper alloy one?
-still cant figure out why im getting 0 ohms to the outside of box/neutral...its a 1976 square d box

1) The screw has to be long enough, and the proper size/threads to engage into the pre-threaded hole in the enclosure.

2) That "silver" wire is most likely aluminum. Use a clamp rated for aluminum connections.

3) You are reading -0- ohms simply because there are bare wires that are connected to the neutral bar that are also touching the enclosure. But simply touching is not sufficient for proper bonding. So, either use a bonding screw, or a short jumper wire of sufficient size from the neutral bar to a lug bolted to the enclosure.

 

[Stubbie]

No. Look up and to the right. There is the hole.

I agree JV ... that is the hole for the bonding screw. Not the one on the bottom left. The correct one is circed in black. I meant for the red cirles to mean no bond screw in those holes.

 

[hidden1]

ok thanks,i wasnt sure about putting a aluminum clamp on copper pipe

 

[hidden1]

I noticed that pic had a screw near top middle(neutral bar) that mine did not have in it .What does that one go to/do?

 

[hidden1]

Can i use this style for bonding-

 

[hidden1]

Can i use this style on bonding?

 

[Jim Port]

I think the bond screw is just to the right of the large neutral lug.

 

[hidden1]

-so some of them did NOT use the green ones with the old 40+ year boxes

 

[Stubbie]

-so some of them did NOT use the green ones with the old 40+ year boxes

Probably not but but the vast majority are green but it is not always real apparent. If you look back at my previous post I circled the bonding screw hole.

 

[Stubbie]

Can i use this style on bonding? View attachment 60732

Yes but if you by that factory it may not be bent correctly for the right height. Just buy a grounding lug/terminal like this and use some #4 bare copper or #4 green insulated stranded copper. Use a machine screw not a sheet metal screw to mount to the panel back. The best thing is to just go to a electrical supply and get the correct bonding screw and install it