Is a double tap permitted for bonding?

Originally Posted By: Russell Frame
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Installing a new service panel and have a quick question.


Is it a no-no to double tap the grounding lug on the ground bus with the cable that's being used to bond the neutral bus?

I'm assuming it is not ok and that a seperate lug should be used or a bonding clamp should be connected to the ground cable directly...

Thanks,
Russ


Originally Posted By: phinsperger
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I think I just heard a vein pop in Joe Tedesco’s forehead. icon_lol.gif



.



Paul Hinsperger
Hinsperger Inspection Services
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Originally Posted By: jhagarty
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Is that a Yes or No?



Joseph Hagarty


HouseMaster / Main Line, PA
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Phone: 610-399-9864
Fax : 610-399-9865

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Originally Posted By: jtedesco
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icon_lol.gif



Joe Tedesco, NEC Consultant


www.nachi.org/tedescobook.htm

Originally Posted By: jpeck
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Russ,


That is a really big NO!

More like a No, no, no, no and NO.


--
Jerry Peck
South Florida

Originally Posted By: Russell Frame
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Where is it prohibited?


Please provide a reference.

Thanks.


Originally Posted By: Greg Fretwell
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It will get back to the listing of the lug and if this lug is part of the panelboard, the listing of the panelboard. Can’t you find a lug on the neutral bus that can hold this bonding jumper? Bus lugs usually hold up to #4. (the typical bonding jumper for 200a)


They also make “twofer” adapters that use 2 smaller holes for a larger conductor.


Originally Posted By: Russell Frame
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There is a large lug on the neutral bus, right next to the main feed…no problem there. It’s the ground bus that’s the problem. Only one large lug, it’s a huge lug so there’s lots of room (like 2/0 size).


Oh well not a big deal, I can pick up another lug....just stuck it in there for now and got to thinking about it.


Originally Posted By: Greg Fretwell
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I am not sure I understand the problem.


The neutral from the service goes in the big lug on the neutral lug.


Is this the jumper between the neutral bus and the ground bus that you are installing? If so it should fit in one of the smaller neutral bus holes it it is #4.


Legally the green screw and the attaching screws from the ground bus to the can is your jumper but I like a piece of wire there too.


Originally Posted By: Russell Frame
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Yeah the neutral from the service is in the large neutral lug, but there is another smaller lug right next to the service lug (which I assume is for bonding).


I dont understand how the can can be your bonding connection? What if this weren't being used as service equipment...how would you 'turn off' bonding?

I'll take a picture this morning so you can see what I've been trying to describe.


Originally Posted By: Greg Fretwell
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The neutral bus should not be permanently bonded to the can. There should be a green screw in a bag. If this is a sub you should be installing a supplimental grounding bus for your EGCs. Personally I prefer a hard wire grounding jumper when you installl a supplimental grounding bus in the “main” for a bonding jumper but the code allows the screw alone.


Originally Posted By: jpeck
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If the service disconnect enclosure is ‘Rated for Service Equipment ONLY’, then the neutral terminal bar IS permanently attached to the enclosure (ground).


If it is 'Rated for Service Equipment' (no "Only"), then the neutral terminal bar (neutral bus) is isolated from ground. When used as 'Service Equipment', the neutral terminal bar MUST be bonded to the enclosure (ground). When not used as 'Service Equipment', the neutral is left isolated from ground.

Neutrals MAY NOT BE multiple tapped. Only one conductor is allowed per neutral terminal. Equipment ground terminals, on the other hand, are frequently (but not always) rated for 2 conductors of the same size.

Everything is spelled out in the label on the enclosure.


--
Jerry Peck
South Florida

Originally Posted By: Russell Frame
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Yes, that’s what I’m talking about. I’m not double tapping the neutral, I’m double tapping the ground lug. I couldn’t find anything on the labels to specify what the ground lug is rated for…but I’ll look again.


Originally Posted By: mmason
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Hello


I personally would never recommend double tapping anything. You run the risk that you might loose, solid electrical conduction. ![icon_rolleyes.gif](upload://iqxt7ABYC2TEBomNkCmZARIrQr6.gif)

The only instance where I feel double tapping is Ok is when you have an approved connection device specifically made for that purpose. Thier is all kinds of great ways to connect wires together. The best in my opinion are the connectors that have a bolt on them that you can really crank down hard on the wires. But not too hard.

Then their is many options for insulating them from very thick insulating tape to plastic or composite cover to insulate. When in doubt alwyas ask a certified electrician that knows his stuff. I think the commercial electricians are a little better qualified than a residential electrician


--
Michael J. Mason
Mason Home Inspection
California Capitol NACHI Chapter President

Originally Posted By: jfarsetta
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Jerry,


I do believe that some panelboard manufacturers okay double lugs for neytrals under the same screw. I dont particularly like to see it, but was recently corrected that the bus bar and screws were, indeed, rated for it. It depends on what the tag says the panel is rated for.


--
Joe Farsetta

Illigitimi Non Carborundum
"Dont let the bastards grind you down..."

Originally Posted By: Bob Badger
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Joe that is true you may still find panels that have neutral bars rated for more than one terminal.


However there is a section in the NEC (408.21) that prevents doing this.

I do not know when that section went in, it may be new for the 2002 NEC and of course panels installed before that section was put in are not an issue.

Anything new can not have more than one neutral per conductor. Well there is one exception for parallel conductors. The wires would be 1/0 or larger and the lug would have to be listed for two conductors.

Bob


--
Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum

Originally Posted By: jfarsetta
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Guys are doing it on almost every new panelboard I see. AHJ is okaying it. I’d love to see the reference. Truly.



Joe Farsetta


Illigitimi Non Carborundum
"Dont let the bastards grind you down..."

Originally Posted By: Bob Badger
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Joe are they under the 2002 NEC?


Here is the section


2002 NEC
Quote:
408.21 Grounded Conductor Terminations.
Each grounded conductor shall terminate within the panelboard in an individual terminal that is not also used for another conductor.

Exception: Grounded conductors of circuits with parallel conductors shall be permitted to terminate in a single terminal if the terminal is identified for connection of more than one conductor.


It has worked OK for years, but the rules have changed.

But if the AHJ is OK with it, is it still worth calling out? ![icon_confused.gif](upload://qv5zppiN69qCk2Y6JzaFYhrff8S.gif)


--
Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum

Originally Posted By: Ryan Jackson
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Bob 408.21 is new for the 2002, but it was put in to match the UL standard on grounded conductor terminals which didn’t allow more than one nuetral per terminal.



Ryan Jackson, Salt Lake City

Originally Posted By: jtedesco
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The exception is referring to the two white wires, they are the grounded conductors run in parallel, and if that lug was designed for more than one, that is what is considered.


See 310.4

![](upload://A7InpVEHO5gyHdei0wKUOxQcOMM.jpeg)


--
Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm