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#178203 - 05/25/08 09:46 PM Where is the neutral-to-ground bond?
SolarPowered Offline
Member

Registered: 07/05/04
Posts: 615
Loc: Palo Alto, CA, USA
Consider the following scenario: Meter is on the outside of a house. RMC goes through the wall into an auxiliary gutter. Inside the gutter Polaris connectors are used to split the service three ways. The gutter then nipples into three main-breaker panels.

Where is the correct place to bond the neutral to ground?

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#178204 - 05/26/08 03:24 AM Re: Where is the neutral-to-ground bond? [Re: SolarPowered]
Tom Offline
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Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
All metal parts of the service must be bonded to the neutral, so you'll have to bond the gutter with a jumper to the neutrals. Each metal pipe nipple must be bonded (at one end), either with a grounding locknut that does not encouter any remaing cocentric/eccentric knockouts or with a grounding bushing with the proper sized jumper . Finally, each panel must be bonded, generally using the screw or wire provided by the manufacturer.
_________________________
Few things are harder to put up with than the annoyance of a good example.

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#178207 - 05/26/08 06:40 AM Re: Where is the neutral-to-ground bond? [Re: Tom]
BPHgravity Offline
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Registered: 04/08/03
Posts: 141
Loc: Port Charlotte, Florida
In short, everything metal on the line side of the service disconnecting means must be bonded together, to the gounded service conductor, the grounding electrode system, and the feeder equipment grounding conductors.

Keep in mind that 250.6 must be complied with which may require an alteration of the bonding and gronding methods used.

The code is inconsistent with how it handles the flow of electrons on the line side of the service verses the load side of the service. It's on of the many aspects of Article 250 I have never been a big fan of.
_________________________
Bryan P. Holland, ECO.
Secretary - IAEI Florida Chapter

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#178211 - 05/26/08 08:35 AM Re: Where is the neutral-to-ground bond? [Re: BPHgravity]
renosteinke Offline
Cat Servant
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Registered: 01/22/05
Posts: 5299
Loc: Blue Collar Country
In general, the ground / neutral bond is made at the first overcurrent device. So, if the meter has a main breaker (or fuse) as a disconnect, then that's where the two are joined. If there is simply a disconnect - no breaker until you get to the panels ... then the bond is made at those panels.

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#178212 - 05/26/08 08:39 AM Re: Where is the neutral-to-ground bond? [Re: BPHgravity]
renosteinke Offline
Cat Servant
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Registered: 01/22/05
Posts: 5299
Loc: Blue Collar Country
In general, the ground / neutral bond is made at the first overcurrent device. So, if the meter has a main breaker (or fuse) as a disconnect, then that's where the two are joined. If there is simply a disconnect - no breaker until you get to the panels ... then the bond is made at those panels.

Finally, let's not get confused about that little green screw. All it does is bond the box to the neutral bar. If you have a separate ground buss, you really ought to have a wire connecting the busses together. I believe the 08 actually says this ... but it seems logical; I wouldn't expect that screw's connection to be reliable enough to use it as the only means of carrying the full fault current of a circuit.

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#178215 - 05/26/08 09:04 AM Re: Where is the neutral-to-ground bond? [Re: renosteinke]
SolarPowered Offline
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Registered: 07/05/04
Posts: 615
Loc: Palo Alto, CA, USA
 Originally Posted By: renosteinke
... then the bond is made at those panels.

So if there are three panels, then you bond the neutral in three places? That would seem to be a violation of 250.6.

From a strictly engineering perspective, what would make the most sense from a "flow of electrons" point of view is to have ground/neutral splice point or bus in the gutter to which you connect the incoming neutral, the neutrals to all the panels, the grounding electrode conductor, bonding wires that go the the ground buses in the panels, and any miscellaneous bonding wires for the gutter & c. But I'm not sure that would be allowed in an auxiliary gutter.

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#178220 - 05/26/08 10:24 AM Re: Where is the neutral-to-ground bond? [Re: SolarPowered]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5299
Loc: Blue Collar Country
It may seem contrary to the usual practice ... but absent a main breaker for all three panels, you have three 'main' panels, as each is the 'first point' of connection to the utility service.

Now, running the GEC to the ground electrode is another matter. I can see the argument that you need to run three GEC's - one from each panel - to the electrode ..... as well as the counter that one building only needs one GEC.

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#178223 - 05/26/08 11:18 AM Re: Where is the neutral-to-ground bond? [Re: renosteinke]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
_________________________
Greg Fretwell

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#178230 - 05/26/08 01:38 PM Re: Where is the neutral-to-ground bond? [Re: gfretwell]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5299
Loc: Blue Collar Country
Greg, thanks for the pics ... seems I've been 'close, but not perfect' in my practices.

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#178232 - 05/26/08 01:44 PM Re: Where is the neutral-to-ground bond? [Re: gfretwell]
SolarPowered Offline
Member

Registered: 07/05/04
Posts: 615
Loc: Palo Alto, CA, USA
 Originally Posted By: gfretwell
This is the picture from the 2002 handbook

http://esteroriverheights.com/electrical/gec_tap.jpg

In that example you will have substantial current flowing in nipples and the metal of the trough. That doesn't seem like it should be correct.

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