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hidden1 11-16-2012 07:10 PM

grounded/bonded
 
5 Attachment(s)
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? Attachment 60615Attachment 60616
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)Attachment 60617Attachment 60618Attachment 60619

kbsparky 11-16-2012 09:59 PM

1 Attachment(s)
Here is where it should be:

hidden1 11-16-2012 10:34 PM

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

Stubbie 11-16-2012 11:31 PM

Quote:

Originally Posted by hidden1 (Post 1053930)
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 11-17-2012 07:42 AM

Quote:

Originally Posted by stubie (Post 1053964)
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 11-17-2012 11:12 AM

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 11-17-2012 11:23 AM

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 11-17-2012 04:53 PM

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. 11-18-2012 11:07 AM

Quote:

Originally Posted by kbsparky (Post 1053911)
Here is where it should be:

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

hidden1 11-18-2012 02:25 PM

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 11-18-2012 03:54 PM

Quote:

Originally Posted by hidden1 (Post 1055272)
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 11-18-2012 05:53 PM

1 Attachment(s)
Quote:

Originally Posted by J. V. (Post 1055127)
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 11-18-2012 05:53 PM

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

hidden1 11-18-2012 07:10 PM

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 11-18-2012 07:20 PM

Can i use this style for bonding-


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