Bonding of a trough

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Dexie123

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Hey all,

I saw this picture on the net and was hoping someone can clear up some confusion. If the neutral in this picture is bonded in the trough and at the the switches where the main disconnects are isn't this not a violation?
 

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augie47

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To my knowledge the "exception" is not specifically addressed but redundant ground paths set up by neutral bonding of service raceways & equipment is accepted.
You have a similar situation when a bonded meter can and service disconnect are connected by a metallic raceway.
 
Hey all,

I saw this picture on the net and was hoping someone can clear up some confusion. If the neutral in this picture is bonded in the trough and at the the switches where the main disconnects are isn't this not a violation?

No, maybe, perhaps.......People often cite "parallel paths for neutral current" as a violation and/or something to be avoided, however this term appears in the NEC specifically for separately derived systems and not generally. The correct term is "objectionable current." see 250.6. This generally isnt enforced much for services, although IMO, the wording is there to require you to set up your bonding jumpers as you would at an SDS, or use a non-metallic raceway. The big loophole though is that "objectionable current" is not defined.
 

augie47

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The big loophole though is that "objectionable current" is not defined.

Good point :thumbsup:
 

PetrosA

Senior Member
This is just my way of thinking, but to me objectionable current is current where an average person wouldn't expect it like at a water meter. The water meter isn't part of the electrical system per se, but can certainly carry harmful current and needs a jumper bonded around it. The current through bonds of different pieces of electrical equipment that aren't usually disassembled under energized conditions (like a metal raceway between meter socket and service disconnect) won't hurt anyone, therefore isn't "objectionable."
 

kwired

Electron manager
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NE Nebraska
This is just my way of thinking, but to me objectionable current is current where an average person wouldn't expect it like at a water meter. The water meter isn't part of the electrical system per se, but can certainly carry harmful current and needs a jumper bonded around it. The current through bonds of different pieces of electrical equipment that aren't usually disassembled under energized conditions (like a metal raceway between meter socket and service disconnect) won't hurt anyone, therefore isn't "objectionable."
Yet the way we connect the GES to water lines means there will be instances where current is normally going to be flowing through said water meter. When everything is in new/good condition opening the circuit by removing that meter doesn't subject the person doing so to much risk though, later on when some things have had a chance to deteriorate is when those installations can be a high risk if conditions are right. A neutral in parallel with a metal raceway between meter socket and service disconnect is an example where the risks are not generally that high, yet the function of the raceway is not to carry current though it will anyway.

Metal service raceways however do have a little stricter requirement to be bonded by more then just a standard locknut which does help some with what risk is there.
 

ActionDave

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.....This generally isnt enforced much for services, although IMO, the wording is there to require you to set up your bonding jumpers as you would at an SDS, or use a non-metallic raceway.....
I don't see how. For an SDS the first disconnect is the same as the service disconnect and you are allowed to bond the neutral there when you use a metallic raceway.
 

kwired

Electron manager
Location
NE Nebraska
I don't see how. For an SDS the first disconnect is the same as the service disconnect and you are allowed to bond the neutral there when you use a metallic raceway.

For a SDS you usually get the choice of bonding whatever conductor that will be the grounded conductor either at the source or at the first disconnecting means, possibly both but to do so there must not be any conductive paths between the two.

For a service it is different in the fact that the grounded conductor must be bonded to pretty much every enclosure it has terminations in as well as in the service disconnecting means enclosure, and there is no such thing as equipment grounding conductor until you are past the main bonding jumper, everything is bonded to the grounded service conductor ahead of the service disconnect.
 

Strathead

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Excellent discussion and it is one of those things I have looked in to before, and decided, "It's the way they let us do it, so accept it."

BTW, for me "objectionable current" is any current that passes through any part of my body. :)

I also object to any current that burns up my expensive electronics.:angel:
 

don_resqcapt19

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The code only prohibits multiple points of connection between the grounding and grounded conductors on the load side of disconnect. On the line side of the disconnect the grounded conductor is permitted to be used for both purposes.
 
For a service it is different in the fact that the grounded conductor must be bonded to pretty much every enclosure it has terminations in as well as in the service disconnecting means enclosure, and there is no such thing as equipment grounding conductor until you are past the main bonding jumper, everything is bonded to the grounded service conductor ahead of the service disconnect.

I don't see how. For an SDS the first disconnect is the same as the service disconnect and you are allowed to bond the neutral there when you use a metallic raceway.

But you dont need to bond the neutral (directly) to every enclosure it passes through, you can use a bonding jumper or raceway to avoid setting up a "parallel path". Consider a meter socket connected to a pull box with EMT or GRC, then PVC from there to the service disconnect. One option is to hit the box with the neutral as it passes by, or you could use a bonding jumper from the box back to the meter, or you could use the raceway to bond the box back to the meter socket if you used a bonding locknut on both ends. The latter two methods don't create a situation where neutral currrent is flowing over raceways. so it can be done (not saying I go out of my to do it this way if it doesnt suit me :angel:)
 

infinity

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The code only prohibits multiple points of connection between the grounding and grounded conductors on the load side of disconnect. On the line side of the disconnect the grounded conductor is permitted to be used for both purposes.

I agree, the line side can have many metallic components, utility end boxes, CT cabinets, meter enclosures, crown boxes, metallic raceways, etc. all of which will be connected to the service neutral conductor. Parallel paths for the neutral current are unavoidable and code compliant on the line side of the service disco when using metallic components.
 
In the supply side, line side, ahead of the first point of disconnect (service), any conductor whether it is a metallic enclosure or a conductor, is in parallel with the grounded (neutral) conductor. If the installation is properly installed.


Most instances of current flowing in the incoming waterpipe (if metallic), is current created by the utility company, via their neutral return current.
There are other instances that can create the current, such as a neighbor sharing a utility transformer and they loose their neutral. And the water pipe supply in the street is continuous between houses.
 
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