Panel Enclosure not to Carry Neutral Current

[Little Bill]

Will someone help me, my brain is either fuzzy or I'm blind!:ashamed1:

I'm looking for the article/code that says you can't use the metal of a panel enclosure to carry the neutral current.
IOW, you have to use the neutral bar and not just a bar that is mounted/bonded to the enclosure.

This would be for the main/service panel.

Thanks

 

[Volta]

I'd call it thus.

200.2 General. Grounded conductors shall comply with
200.2(A) and (B).
(A) Insulation. The grounded conductor, where insulated,
shall have insulation that is (1) suitable, other than color,
for any ungrounded conductor of the same circuit on circuits
of less than 1000 volts or impedance grounded neutral
systems of 1 kV and over, or (2) rated not less than
600 volts for solidly grounded neutral systems of 1 kV and
over as described in 250.184(A).
(B) Continuity. The continuity of a grounded conductor
shall not depend on a connection to a metallic enclosure,
raceway, or cable armor.

 

[Fulthrotl]

Will someone help me, my brain is either fuzzy or I'm blind!:ashamed1:

I'm looking for the article/code that says you can't use the metal of a panel enclosure to carry the neutral current.
IOW, you have to use the neutral bar and not just a bar that is mounted/bonded to the enclosure.

This would be for the main/service panel.

Thanks

old panels have had a bar just bolted to the can, with the neutral landed on it,
and every neutral and ground landed there as well.

then.... we went to an isolated neutral buss, with the grounds separated from
the neutrals, and the ground buss bolted directly to the can.

then...... we went to isolated neutral and separated isolated ground buss'es,
with a bonding wire landing the isolated ground buss to the can.....

so, i figure the next strategy would be to isolate the neutrals and grounds,
and ground one leg of the panel, as is done sometimes in 3 phase delta panels.

that should provide maximum confusion. :huh::huh::huh:

as for the original question, you have ungrounded conductors, grounded conductors,
and grounding conductors. an enclosure is not a conductor, it's an enclosure, so
you can't use it for a conductor.

unless of course, you are in mexico, or india. different rules apply.

 

[Smart $]

Will someone help me, my brain is either fuzzy or I'm blind!:ashamed1:

I'm looking for the article/code that says you can't use the metal of a panel enclosure to carry the neutral current.
IOW, you have to use the neutral bar and not just a bar that is mounted/bonded to the enclosure.

This would be for the main/service panel.

Thanks

Actually, I don't think there is anything which specifically prohibits using a a busbar which is mounted/bonded to the enclosure... but the service/feeder grounded/neutral conductor must be directly connected to it, and as such the GEC(s). If there is a neutral busbar to which the service/feeder grounded/neutral conductor is connected and the busbar mounted to panel is connected via a main/system bonding jumper, then you cannot connect branch and feeder circuit grounded/neutral conductors to it. Whichever way it is connected, the requirements are implicit rather than explicit (unless my forgetfulness is getting worse :ashamed1

 

[Joe Villani]

Panel Enclosure not to Carry Neutral Current

This bring up a situation I am looking for opinions on:

Given: A typical 200 amp residential service.

Grounded (neutral) conductor factory bonded to meter pan.

Electrician uses metallic raceway as permitted by article 230 between meter panel and electrical panel.

Main bonding jumper installed in electrical panel.

Would this be in conflict with 200.2(b)?

Could an inspector fail the installation as current flow on all paths?

Just looking for opinions

Thanks,

Joe

 

[don_resqcapt19]

This bring up a situation I am looking for opinions on:

Given: A typical 200 amp residential service.

Grounded (neutral) conductor factory bonded to meter pan.

Electrician uses metallic raceway as permitted by article 230 between meter panel and electrical panel.

Main bonding jumper installed in electrical panel.

Would this be in conflict with 200.2(b)?

Could an inspector fail the installation as current flow on all paths?

Just looking for opinions

Thanks,

Joe

As long as there are no additional grounded to grounding connections downstream from the service panel there are no code issues or parallel paths for the grounded conductor current.

 

[texie]

On a similar subject, is it also correct to require the GEC to be connected directly to the neutral bar, as opposed to connecting to the enclosure? I seem to recall that this is only OK if there is a wire type bonding jumper from the neutral bar to the equipment ground bar.

 

[jumper]

On a similar subject, is it also correct to require the GEC to be connected directly to the neutral bar, as opposed to connecting to the enclosure? I seem to recall that this is only OK if there is a wire type bonding jumper from the neutral bar to the equipment ground bar.

250.24 Grounding Service-Supplied Alternating-Current
Systems.
(A) System Grounding Connections. A premises wiring
system supplied by a grounded ac service shall have a
grounding electrode conductor connected to the grounded
service conductor, at each service, in accordance with
250.24(A)(1) through (A)(5).
(1) General. The grounding electrode conductor connection
shall be made at any accessible point from the load end
of the service drop or service lateral to and including the
terminal or bus to which the grounded service conductor is
connected at the service disconnecting means.

 

[kwired]

as for the original question, you have ungrounded conductors, grounded conductors,
and grounding conductors. an enclosure is not a conductor, it's an enclosure, so
you can't use it for a conductor.

unless of course, you are in mexico, or india. different rules apply.

What about using metallic raceways for equipment grounding? How does the equipment grounding conductor get from the main bonding jumper to the raceways at the service equipment? Would seem to me it does rely on the metal enclosure to complete this path and is permitted to be done that way by 250.96.

 

[Smart $]

What about using metallic raceways for equipment grounding? How does the equipment grounding conductor get from the main bonding jumper to the raceways at the service equipment? Would seem to me it does rely on the metal enclosure to complete this path and is permitted to be done that way by 250.96.

I believe he meant an enclosure cannot be used as a circuit conductor.

 

[kwired]

I believe he meant an enclosure cannot be used as a circuit conductor.

I'm not so sure that is what he meant and the reason for my response. He did mention "you have ungrounded conductors, grounded conductors,and grounding conductors." Plus "an enclosure is not a conductor"

IMO an enclosure can be a grounding conductor. It is correct that it can not be used as a circuit conductor.

 

[Little Bill]

I'd call it thus.

Thanks! 200.2(B) is what I was looking for

as for the original question, you have ungrounded conductors, grounded conductors,
and grounding conductors. an enclosure is not a conductor, it's an enclosure, so
you can't use it for a conductor.

unless of course, you are in mexico, or india. different rules apply.

I understand the rule, I just couldn't find it, "old timer's disease" kicking in.:weeping:

Actually, I don't think there is anything which specifically prohibits using a a busbar which is mounted/bonded to the enclosure... but the service/feeder grounded/neutral conductor must be directly connected to it, and as such the GEC(s). If there is a neutral busbar to which the service/feeder grounded/neutral conductor is connected and the busbar mounted to panel is connected via a main/system bonding jumper, then you cannot connect branch and feeder circuit grounded/neutral conductors to it. Whichever way it is connected, the requirements are implicit rather than explicit (unless my forgetfulness is getting worse :ashamed1

I don't understand why you can't land neutrals on a bus/bar that is bonded to the can if it has a bonding jumper. You are not relying on the enclosure for continuity.

On a similar subject, is it also correct to require the GEC to be connected directly to the neutral bar, as opposed to connecting to the enclosure? I seem to recall that this is only OK if there is a wire type bonding jumper from the neutral bar to the equipment ground bar.

Correct 250.24(A)(4) wire or busbar

 

[Volta]

...
I don't understand why you can't land neutrals on a bus/bar that is bonded to the can if it has a bonding jumper. You are not relying on the enclosure for continuity.
...

Well, if the MBJ is a wire you can, if it is a steel enclosure, you can't.

 

[Little Bill]

Well, if the MBJ is a wire you can, if it is a steel enclosure, you can't.

I researched this a little more after I posted that. According to the handbook, if you use a bar directly mounted to the enclosure and that has a main bonding jumper, the neutral current would also be carried by the enclosure. That would put unwanted current on the enclosure.

I don't think 200.2(B) was put into the code until the 2008.

 

[Smart $]

I'm not so sure that is what he meant and the reason for my response. He did mention "you have ungrounded conductors, grounded conductors,and grounding conductors." Plus "an enclosure is not a conductor"

IMO an enclosure can be a grounding conductor. It is correct that it can not be used as a circuit conductor.

Exactly..."an enclosure is not a [circuit] conductor"

 

[Smart $]

...

I don't understand why you can't land neutrals on a bus/bar that is bonded to the can if it has a bonding jumper. You are not relying on the enclosure for continuity.

...

Well, if the MBJ is a wire you can, if it is a steel enclosure, you can't.

The supply neutral (or supply "neutral jumper" ) must be directly connected to the terminal bar. FWIW, a jumper cannot be both a "neutral jumper" and a main/system bonding jumper. From a technical perspective, it's all in what you call the jumper, but if you call it a "neutral jumper", you are still required to install, in addition to the "neutral jumper", a main/system bonding jumper, which technically could be the mounting screw(s) of the "grounding" terminal busbar. Of course, a "neutral jumper" is required to be of a wire or busbar type.

 

[Little Bill]

The supply neutral (or supply "neutral jumper" ) must be directly connected to the terminal bar. FWIW, a jumper cannot be both a "neutral jumper" and a main/system bonding jumper. From a technical perspective, it's all in what you call the jumper, but if you call it a "neutral jumper", you are still required to install, in addition to the "neutral jumper", a main/system bonding jumper, which technically could be the mounting screw(s) of the "grounding" terminal busbar. Of course, a "neutral jumper" is required to be of a wire or busbar type.

See my post #14

 

[Smart $]

See my post #14

I researched this a little more after I posted that. According to the handbook, if you use a bar directly mounted to the enclosure and that has a main bonding jumper, the neutral current would also be carried by the enclosure. That would put unwanted current on the enclosure.
...

That's if the supply neutral is connected to a neutral terminal busbar, MBJ from busbar to enclosure (such as with a typical loadcenter bonding screw), enclosure to grounding terminal bar. If the MBJ connected directly from neutral busbar to grounding busbar, the current would not travel through the enclosure, that is ignoring the portion that would go through the grounding system regardless of connections. Nonetheless, the MBJ is not to carry neutral current by design.

 

[Little Bill]

That's if the supply neutral is connected to a neutral terminal busbar, MBJ from busbar to enclosure (such as with a typical loadcenter bonding screw), enclosure to grounding terminal bar. If the MBJ connected directly from neutral busbar to grounding busbar, the current would not travel through the enclosure, that is ignoring the portion that would go through the grounding system regardless of connections. Nonetheless, the MBJ is not to carry neutral current by design.

Probably about 400 billion incorrect installs out there then (not counting incorrect sub panel grounding/bonding).

Usually if the neutrals and EGCs are allowed to be bonded, the neutrals are landed on any bus/bar in the panel.
I've never had nor heard of an inspector flagging anyone for this unless it was a sub panel.:happyno:

Might be because 200.2(B) wasn't in the code until the 2008.

 

[PetrosA]

Probably about 400 billion incorrect installs out there then (not counting incorrect sub panel grounding/bonding).

Usually if the neutrals and EGCs are allowed to be bonded, the neutrals are landed on any bus/bar in the panel.
I've never had nor heard of an inspector flagging anyone for this unless it was a sub panel.:happyno:

Might be because 200.2(B) wasn't in the code until the 2008.

OTOH, every panel I've seen since I started back in the 80s had a bar of some sort joining the neutral bars in them. I've never seen one with two separate neutral bars bonded by screws to the enclosure. Some panels have a removable connecting bar so the panel can be converted to a sub panel, but I've never seen one shipped with separated bars...