200 amp panel for new basement: ground and neutrals on same bus

hammickJanuary 19, 2009

Guys:

I hired an electrician to wire my new basement (previously unfinished). He installed a 200 amp cutler hammer box right next to the main house box (which is also a 200 amp cutler hammer). He fed the basement box using two 100 amp breakers that he located in the main box. The main box is full and the basement box is about half full.

The main panel has the grounds and neutrals intermixed on both bus bars and it is my understanding code allows this. The basement panel also has grounds and neutrals mixed on both busses. My understanding is that on subpanels grounds and neutrals must be separated.

Is my basement panel considered a subpanel? When I turn off the two 100 amp breakers in the main panel feeding the basement panel the basement panel has absolutely no power in it.

If it is a subpanel do I need to have it rewired? Thanks.

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bus_driver

The new panel is a subpanel.

    Bookmark   January 19, 2009 at 7:49PM
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billhart

Yes it is a subpanel. By my understanding of the code the subpanel neutral should be isolated from ground. Since the panels are right next to each other it isn't as important as if they were far apart, but I don't think the code has any distance waiver. It should be a simple fix.

    Bookmark   January 19, 2009 at 7:51PM
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hammick

Yes they are only separated by several inches. Each 100 amp breaker from the main panel has a very thick wire feeding the 200 amp breaker in the sub panel. There is a third very thick wire from the ground/neutral bus in the main panel feeding the ground/neutral buses in the sub panel (they are bonded together in the sub panel the same way they are in the main panel.

I want to make sure I understand this correctly before I call the electrician and complain (or better yet hire an electrician that knows what he is doing).

    Bookmark   January 19, 2009 at 8:07PM
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bus_driver

Your latest post indicates paralleled conductors feeding the subpanel. The rules are very specific for those. Did your installer comply? Can't tell from here, but my bet is "no". The whole situation begins to look like it was done by an amateur.

    Bookmark   January 19, 2009 at 8:52PM
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jmvd20

The thing that is getting me right now is the mention of "2 100 amp breakers". Hammick, when you say that do you mean there are 2 breakers with a handle that ties them together?

At any rate, since your new panel is a sub-panel the grounds and neutrals should be seperated. This would require the installation of a seperate ground bar in the sub-panel, as well as a 4th wire from the ground/neutral bar in the main panel to the ground bar in the sub-panel. It shouldn't be a big deal for them to take care of this, although Im not sure why it wasn't done in the first place.

    Bookmark   January 19, 2009 at 10:43PM
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hammick

Yes the handle ties the 100 amp breakers together. Is there another problem other than the ground and neutrals not being separated?

    Bookmark   January 19, 2009 at 10:52PM
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jmvd20

No additional problem, I just wanted to make sure I was understanding your description of the breaker correctly.

    Bookmark   January 19, 2009 at 11:14PM
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hammick

Thanks for the info guys. I powered down the sub panel and put all the grounds on the left and the neutrals on the right. They are still bonded together as I only have three feeds form the main. I plan to run another feeder from the main panel and have a question about that.

The current feeder goes from the left bus bar at the main out the same hole as the hot feeds. It hooks into the right side (neutral) bus of the sub. For the new feeder that will go to the left side (ground) bus of the sub can I share the same lug at the main that the neutral feeder is using? If not, I will have to buy another lug which is no big deal.

I assume I use the exact same no. 6 wire for the new feeder? Do the neutral and ground feeds have to be the exact same length (like the hot feeds)?

Finally the main service ground wire coming in is attached to the right side bus at the main panel. Since by code the neutral and grounds are bonded I assume this is fine?(it passed inspection when the house was built)

Thanks for the help.

    Bookmark   January 27, 2009 at 11:06AM
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pcoonce

I have the same sort of issue. I had a 90 amp panel put on for a 50 amp gfci hot tub right outside of the main panel. I looked inside after he left and didn't see a ground bus. I called him and he said I should put my hot tub ground on the neutral bus. When I questioned him about code he said that I don't need to isolate the two here but any other box after this one ie a seperate building then I would have to isolate them. Is he just wrong or it seems like this ground/neutral subpanel bond use to be code.

    Bookmark   May 11, 2011 at 2:59PM
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brickeyee

"he said that I don't need to isolate the two here but any other box after this one ie a seperate building then I would have to isolate them. Is he just wrong or it seems like this ground/neutral subpanel bond use to be code."

He is just wrong.

Any and every panel after the main is a sub and requires a 4-wire connection (hot-hot-neutral-ground) and that grounds and neutrals be isolated from each other (the grounds are attached to the new box, the neutral may not be).

    Bookmark   May 11, 2011 at 4:25PM
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Ron Natalie

Who is "he?"

Hot tub installers should not be playing electrician. Contractors playing unlicensed electricians is bad enough when it's just a few receptacles, when it becomes a big tank of water that you're going to immerse you and your family into, it's inexcusable.

I'd have someone with a clue look at what else he's done wrong with that installation. If it's one thing the idiots don't understand it's article 680.

    Bookmark   May 11, 2011 at 6:02PM
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brickeyee

"I powered down the sub panel and put all the grounds on the left and the neutrals on the right. They are still bonded together as I only have three feeds form the main. "

you are very likely to need to add a separate grounding bar to the panel, and possibly two (one on each side).

the green bonding screw that ties the neutral bar to the box itslef must be removed.

Some panels allow you to remove the bonding between the tqro strips so that one can be used for grounds, the other for neutral but this tends to make a real mess in the panel since every grounded circuit now needs to go separately to each bar.

It is often worth the effort to add two grounding bars parallel to the existing neutral bars.

This allows the neutral and ground for each circuit to be tied to the respective bars adjacent to the breaker feeding the hot for that circuit.

It sounds like you need four #6 connections (though it might be possible to use a smaller ground line).

The hots come from a breaker in the main, and the neutral and ground both come from the same point in the main but need to land on their separate bars in the sub.

The reason ground and neutral are separated in sub panels is to prevent any current sharing between the ground connection back to the main and the neutral connection.

Any voltage drop in the ground connection picks up the grounds in the sub-panel and the ground of every branch circuit is is supplying.
Grounds are never supposed to carry current, except during a fault.
You want the whole set of grounds to be as close to zero volts as possible.

    Bookmark   May 12, 2011 at 11:24AM
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