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Old 05-11-2011, 05:22 PM   #1
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Service panel ground


While I have been working on a sub-panel and run into questions about the wiring there, I finally got around to looking in the main panel. See photos. If I am looking at this right, the main panel was never grounded which is likely why the subpanel had wierd (in my mind) wiring.

There is a ground at the meter, but only one bus, which is isolated (floating?) with all the neutrals and grounds connected there. There is a location on the opposite side of the panel for attaching an "equipment ground" but nothing is attached there.

The house was built in the 1970's. Would it be worth the trouble of:
Running a ground from the grounding rod below the meter to the panel?
Running a single neutral conductor from the subpanel? That panel is wired for 240 and I have two hots and a ground which goes back to the main bus where all the neutrals and grounds are bonded together.
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Service panel ground-img_1066a.jpg   Service panel ground-img_1071a.jpg  

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Old 05-11-2011, 05:38 PM   #2
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Service panel ground


ground at the meter? does that wire actually go into the meter can or does it slip behind it and into your panel?

as to the floating terminal; I don't see it in the picture but make sure there isn't a screw that screws clear through the terminal strip and into the metal of the tub. some manufacturers use a small piece of metal that fits into one of the terminal holes and reaches down to the panel tub where it is attached.

and you are saying there is no grounding electrode conductor in that panel at all?

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Old 05-11-2011, 07:11 PM   #3
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Service panel ground


Nap,

The ground wire at the meter might go behind it as you suggest. I really can't tell.

There is only one bus and it is isolated from the panel metal by a plastic spacer. I can't see if a screw goes all the way through with all the wires in there but I think that would defeat the purpose of having it on plastic.

Quote:
and you are saying there is no grounding electrode conductor in that panel at all?
Yep, that's what I think. All the bare copper wires come from a NM "romex" cable, none by itself. Besides that, I would expect that the grounding wire would be larger- the same size as the one outside.

On the right side of the panel wall there is a pre-punched screw hole with a sticker saying for "equipment grounding only." It seems that all the grounding conductors would be on that side opposite the neutral bus and bonded at the specified location.
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Old 05-11-2011, 08:23 PM   #4
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Service panel ground


Quote:
The ground wire at the meter might go behind it as you suggest. I really can't tell.
well, I can't either so we'll skip that for now

Quote:
There is only one bus and it is isolated from the panel metal by a plastic spacer. I can't see if a screw goes all the way through with all the wires in there but I think that would defeat the purpose of having it on plastic.
it is made so it it needs to be isolated, it can. The screw or main bonding jumper is included for when the neutral and ground needs to be bonded. It defeats the isolators intentionally.

If I remember correctly, your panel looks to be a brand that used a little offset piece the looks a lot like this:

No guarantees though. If you look at the screws it should be fairly obvious if one passes through the neutral bar and continues to the panel tub and is screwed in. It also will have a head on it so it could be tightened against the bar. Often times green but not always.



Quote:
Yep, that's what I think. All the bare copper wires come from a NM "romex" cable, none by itself. Besides that, I would expect that the grounding wire would be larger- the same size as the one outside.
if it was installed improperly, the size of the wire could be improper so don't count on just that. make sure all the wires go to an NM cable or the one known obvious one is the neutral service feeder conductor that, along with the hot conductors, goes to the meter.



Quote:
On the right side of the panel wall there is a pre-punched screw hole with a sticker saying for "equipment grounding only." It seems that all the grounding conductors would be on that side opposite the neutral bus and bonded at the specified location.
in a situation (such as a sub panel) you would need to install a ground bar there to land your egc's. In the main service panel you can land the grounds and neutrals on the same bar.
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Old 05-11-2011, 09:27 PM   #5
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Service panel ground


Is the main panel connected to the meter base with rigid conduit?
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Old 05-12-2011, 01:08 AM   #6
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Service panel ground


Could this be the feeder neutral?
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Old 05-12-2011, 05:29 AM   #7
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Service panel ground


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Originally Posted by sirsparksalot View Post
Could this be the feeder neutral?
That would likely be the service neutral.
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Old 05-12-2011, 06:23 PM   #8
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Service panel ground


a7ecorsair,
No sir, the service panel is in the middle of the house.

sirsparksalot,
It's the service neutral. Not sure what you are calling a feeder neutral. I just don't know that term. Can you describe that for me?


If I may digress, the bottom left breaker in this photo feeds a 120/240 circuit to a subpanel. I have some question about this circuit which I addressed in a recent thread. My question here is:
Does anyone see a problem with moving the white hot feed to the neutral bus here and in the subpanel? I don't have a neutral conductor at the subpanel and I don't need the 240 capability.
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Old 05-12-2011, 06:29 PM   #9
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Service panel ground


Typical 70's installation.

It would appear that your panel is fed with type SE-U cable, which has a concentric neutral, but no separate ground. The neutral bar would typically be bonded to the enclosure through a bonding screw, or strap.

But 35-40 years ago, many jurisdictions did not properly enforce the Code for proper bonding and grounding.
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Old 05-12-2011, 06:34 PM   #10
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Service panel ground


it's that thread with the small panel a friend put in?

yes, you can move the white to the neutral bar in this panel.

If so, move the white to the neutral bar but in the subpanel, you have to move the white to the isolated neutral bar and install a ground bar. Then move all the ground conductors to that new ground bar. Your neutrals will land on the isloated neutral bar.

Going to have to check on the need to a grounding electrode system at the subpanel. Seems like 30 amp or less it isn't required if you have a 4 wire feed. Gotta check though.

It still sounds like you need a grounding elecrode conductor in this panel though and your neutral bar and ground needs to be bonded.

Just to be sure, this does not have a disconnect other than the main in this panel somewhere between this panel and the meter?

Is is possible it did at one time?
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Old 05-12-2011, 07:22 PM   #11
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Service panel ground


kbsparky,
1977 actually. This was a rural county then and everyone had the philosophy of "it's my property" and a lot of things were done not exactly kosher. Actually I was a little naive in thinking that since the house was financed through federal Farmers Home Adm that having two separate inspecting agencies would catch anything I didn't know about in my 20's.
Could you explain concentric neutral just a little bit for me please? I don't know how the visible ground plays into this but I did discover one day that the grounding wire was just stuck in the dirt. I was digging a flower bed and thought I had pulled it loose from the grounding rod. Come to find out, there wasn't even a rod there.
Wonder if I could get EMC to come out and check behind the meter?

Nap,
Yep, that's the thread.
Quote:
If so, move the white to the neutral bar but in the subpanel, you have to move the white to the isolated neutral bar and install a ground bar. Then move all the ground conductors to that new ground bar. Your neutrals will land on the isloated neutral bar.
That's exactly what I was planning on doing. I've already bought a grounding bus.
No other disconnect. Meter, main panel, circuit breaker to feed the subpanel, disconnect in the sub. Never any other disconnect.
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Old 05-12-2011, 07:42 PM   #12
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Service panel ground


Quote:
Originally Posted by downunder View Post
kbsparky....Could you explain concentric neutral just a little bit for me please?....
Here is a pic:



The neutral conductor is split into strands, and concentrically wrapped around the other conductors. Hence the term "concentric" neutral.
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Old 05-13-2011, 12:30 AM   #13
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Service panel ground


Quote:
Originally Posted by brric View Post
That would likely be the service neutral.
yes, that's what I meant
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Old 05-13-2011, 04:46 PM   #14
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Service panel ground


kbsparky,
So would one use the concentric neutral like the ground on a coax. Cut through it a few inches, peel it back and separate it from the hot conductors and tie it into the neutral bus. I'm thinking like I used to do on CB and ham radio coax.

Also, if there was no separate ground, could that be where the ground wire goes to at the meter- tied into the neutral somewhere at the meter?

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Last edited by downunder; 05-13-2011 at 05:25 PM.
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