Neutrals On equipment Ground Bars.

[david]

Re: Neutrals On equipment Ground Bars.

Hurk,
I agree that the enclosure should not be used as a current caring conductor. But I can?t tell you how many equipment ground buses in service panels I have seen added that are used to land the neutral to. It was mentioned that most of these retro fit kits have instructions stated for equipment grounding purposes only. But is their a better code reference then 110.5 that would spell this out in the code?

[ October 02, 2003, 01:15 AM: Message edited by: david ]

 

[hurk27]

Re: Neutrals On equipment Ground Bars.

This is what we can't seem to find that is why I was wondering if it was an UL requirement? which we would also have to follow.

Look at my earlier post

 

[hurk27]

Re: Neutrals On equipment Ground Bars.

David Look at 408.20 Grounding of Panelboards

Grounding conductors shall not be connected to a terminal bar provided for grounded conductors (may be a neutral) unless the bar is identified for the purpose and is located where interconnection between equipment grounding conductors and grounded circuit conductors is permitted or required by Article 250.

 

[david]

Re: Neutrals On equipment Ground Bars.

Hurk,
Close, but someone will argue that it says the equipment ground cant land on the neutral bar when the neutral bar is required to be separated from the equipment ground and this does not spell out that the neutral cannot land on a equipment ground bar in a service panel.

I think some things were so fundamental that there was no need to spell out what seemed so obvious in our trade.

 

[iwire]

Re: Neutrals On equipment Ground Bars.

Thanks guys, some interesting comments here.

Bennie how can you say

I don't think the metal enclosure constitutes an equipment ground conductor

To me 250.118 clearly says it is.
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The "green screw" as scary to me as it may be, must be able to take the full fault current from the POCO if one of the service conductors makes contact with the can.

I doubt highly that it could, but the panels are UL listed. How does this work?

Later I will look through the UL white book and see if the answer to Wayne's question is there.

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Wayne (awwt)

I always believed the green bonding screw was to bond the panel to the buss-- not to bond one buss to another through the panel chassis-- nor to bond the buss to the panel. The screw is a method for the panel to be part of the bond, but not the source of the bond.

There is no requirement for a jumper from neutral bar to ground bar, (at least for a ground bar to be used only for grounds, I think the other Wayne is onto something for a UL required jumper if the bar is to be used for both neutrals and grounds) the panel bond whether a screw, strap or wire is all that is required.

Now when you add an axillary ground bar this bond will take any faults from any size branch circuits connected to it.

This is no different than putting a ground bar in a junction box landing branch circuit grounds there from NM or MC and using EMT as the ground conductor back to the panel. Any faults would pass through the bonding jumper, which is the reason for a bonding jumper in the first place

[ October 02, 2003, 06:06 AM: Message edited by: iwire ]

 

[goldstar]

Re: Neutrals On equipment Ground Bars.

The green screw can be considered a bonding jumper only when metal conduit is the equipment ground conductor.

On a NM cable wiring method, the green screw is only bonding the can to ground.

Do think the green screw is also the bond between the equipment ground and the neutral? It seems that this is all the Code requires as a main bonding jumper between the two. If so the green screw would serve as the effective fault- clearing path for the equipment ground.

I'd like to share a personal experience regarding the green bonding screw. Once (way back when I was a neophyte) I happened to be working in a live panel with most of the live buss exposed. After bringing an NM cable into the panel and stripping off the jacket the EGC whipped around and hit the live buss. It blew the 150 amp main but also completely burnt out the green bonding screw. Since that unfortunate, but very educational, point in time I began to bond the grounding electrode conductor and the EGC from the cold water main to the cabinet at the point of entry by stripping back the insulation and clamping it inside a 1/2" squeeze connector (properly installed in the cabinet) and then terminating it to the neutral/ground buss bar. So, I don't rely on the green bonding screw to be the only means of bonding the neutral bars to the cabinet irrespective of whether it's an NEC or UL minimum requirement.

[ October 02, 2003, 06:08 AM: Message edited by: goldstar ]

 

[iwire]

Re: Neutrals On equipment Ground Bars.

Originally posted by goldstar:

I began to bond the grounding electrode conductor and the EGC from the cold water main to the cabinet at the point of entry by stripping back the insulation and clamping it inside a 1/2" squeeze connector (properly installed in the cabinet) and then terminating it to the neutral/ground buss bar.

Phil that squeeze has no grounding rating, I think if you try to say it is an electrical connection you have a violation.

Gotta get to work talk to you later.

Bob

Why not buy a foot lug that you could land in the panel pass through onto the neutral bar?

 

[pierre]

Re: Neutrals On equipment Ground Bars.

This thread is very interesting, for two reasons. I have never given a thought as to the possibility that the green bonding screw at the main panel was not capable of being the actual bond conductor in conjunction with the can.
The second reason that it is interesting, is how different guys here have come up with their own ideas and then say that is the reason for...
Bennie's comment about the bonding screw being permitted for raceways, but not EGCs makes a lot of sense. The rest of the comments are all very perceptive, but not the 'legal' answer.
So I say contact both the manufacturer and UL for the 'official' answer. I myself will try this later today, then we can be able to say we know the answer.

Pierre

 

[david]

Re: Neutrals On equipment Ground Bars.

Pierre,

I don?t think Bob?s point is the bond screw is not the actual bond conductor. But that the bond screw or for that matter the enclosure should not be a conductor for normal current, (such as neutral current). He is trying to establish that conductors for normal current are identified as copper unless other wise provided for in the code. He has interpreted 310.14 as providing for aluminum as a conductor for normal current. And is basically saying that the metal the enclosure is made of is not a conductor for normal current. He is saying fault current is not normal current.
Well, that is my read on it, and I think he is making a lot of sence.

I got an an inspection schedule for 11:00 check back in some time tonight, later.

[ October 02, 2003, 10:32 AM: Message edited by: david ]

 

[iwire]

Re: Neutrals On equipment Ground Bars.

David, Thank you very much for explaining what I seem to have had trouble explaing.

You "read" on my point is accurate.

Bob

[ October 02, 2003, 04:06 PM: Message edited by: iwire ]

 

[goldstar]

Re: Neutrals On equipment Ground Bars.

Phil that squeeze has no grounding rating, I think if you try to say it is an electrical connection you have a violation.

Gotta get to work talk to you later.

Bob

Why not buy a foot lug that you could land in the panel pass through onto the neutral bar?

Bob,

I realize that a squeeze connector is not a "legal" grounding connection or an "approved & rated" connection for the EGC (if that's all I were using it for). In fact, it's not required anywhere in the NEC or for a breaker panel at all. I only use it as an added measure of grounding because I know that that green bonding screw won't hold up. As far as I know the green bonding screw is all that most manufacturers required for a main breaker panel (as Bennie pointed out).

However, while the squeeze connector is not a "legal" means of grounding by itself, have I committed a code violation by using it in conjunction with the green bonding screw ?

I just took a good look at my (old) 100 amp residential service (I know.....I should have changed it a long time ago........still have FPE breakers too) and it has a piece of armored #8 solid attached to the ground clamp on the cold water main. At the breaker panel it enters the cabinet through a 1/2" squeeze connector and then to the neutral buss. The # 8 and the armor are grounded to the cold water main, the armor and the # 8 are bonded together (internally), the armor is bonded to the cabinet via the squeeze connector and the # 8 is terminated on the neutral bar. What's the difference between this and what I choose to do ?

By the way, the foot lug is a good idea.

Regards,

Phil

[ October 02, 2003, 10:00 PM: Message edited by: goldstar ]