New Service Gear Ampacity versus 100% continuous duty

[david luchini]

IMO the bussing is an integral part of the equipment defined in 408.

Have you never seen a tap from a panelboard or switchboard bus? Or for that matter, a 200A c/b supplying two separate 100A feeders using the tap rules?

Are you suggesting that these types of taps are in violation of the Code because the panelboard bus or breaker lugs are not "feeders?" I wouldn't agree with that interpretation.

 

[kwired]

Have you never seen a tap from a panelboard or switchboard bus? Or for that matter, a 200A c/b supplying two separate 100A feeders using the tap rules?

Are you suggesting that these types of taps are in violation of the Code because the panelboard bus or breaker lugs are not "feeders?" I wouldn't agree with that interpretation.

Or taps made from busways.

368.1 Scope.

This article covers service-entrance, feeder, and branch-circuit busways and associated fittings.

368.2 Definition.


Busway.
A raceway consisting of^ a grounded metal enclosure containing factory-mounted, bare or insulated conductors, which are usually copper or aluminum bars, rods, or tubes.

Art 368 seems to think the bus in a busway is a conductor and can be a part of a feeder, branch circuit or be service conductors. Not exactly the same thing covered in 368 as the bus in a switchboard or panelboard - yet they very possibly could connect directly to one another and effectively become one conductor or bus when that happens.

 

[electrofelon]

Have you never seen a tap from a panelboard or switchboard bus? Or for that matter, a 200A c/b supplying two separate 100A feeders using the tap rules?

Yes many times

Are you suggesting that these types of taps are in violation of the Code because the panelboard bus or breaker lugs are not "feeders?" I wouldn't agree with that interpretation.

Maybe, technically.... I can find a code path wither way. I think there are many gaps, inconsistencies, and conflicts either way and the wording needs to be improved and clarified. We need further clarification on what exactly a conductor is and when a conductor is covered by 310, how and if adjustments are made to a "non 310" conductor, and more details in 310.1 and how it fits in. We also need to know if electrical equipment such as circuit breakers are also feeders. I am going to leave the discussion now as I think we are both entrenched in our opinions/interpretations and you have not responded to any of my ideas like 310.1 so I just feel there is no further point.

 

[kwired]

Yes many times



Maybe, technically.... I can find a code path wither way. I think there are many gaps, inconsistencies, and conflicts either way and the wording needs to be improved and clarified. We need further clarification on what exactly a conductor is and when a conductor is covered by 310, how and if adjustments are made to a "non 310" conductor, and more details in 310.1 and how it fits in. We also need to know if electrical equipment such as circuit breakers are also feeders. I am going to leave the discussion now as I think we are both entrenched in our opinions/interpretations and you have not responded to any of my ideas like 310.1 so I just feel there is no further point.

Don't leave yet, I have something to add in the 310 area.

310.10 Uses Permitted.


The conductors described in 310.104 shall be permitted for use in any of the wiring methods covered in Chapter 3 and as specified in their respective tables or as permitted elsewhere in this Code.

All of 310 is about conductors described in 310.104, they moved that content to near the end of 310 I believe in 2011 though it maybe should still be at the front as it tells us what 310 applies to. All the conductors in 310.104 are "wire type conductors" for general use, but anything that can carry current technically is a conductor, just not an art 310 conductor.

 

[Smart $]

Don't leave yet, I have something to add in the 310 area.



All of 310 is about conductors described in 310.104, they moved that content to near the end of 310 I believe in 2011 though it maybe should still be at the front as it tells us what 310 applies to. All the conductors in 310.104 are "wire type conductors" for general use, but anything that can carry current technically is a conductor, just not an art 310 conductor.

I agree with your 310 assessment.

What appears to be the issue, is whether distribution equipment parts (bus in particular) can be a feeder. If that be the case, please tell me how one can apply the ampacity requirement to panel bus. That is, what is the ampacity of panel bus per Code? I'm asking because 215.2 gets right to the matter of conductor ampacity... and Code does not have any provision for panel bus ampacity.

 

[electrofelon]

All the conductors in 310.104 are "wire type conductors" for general use, but anything that can carry current technically is a conductor, just not an art 310 conductor.

I agree with your 310 assessment.

Ok I'll buy that too

What appears to be the issue, is whether distribution equipment parts (bus in particular) can be a feeder. If that be the case, please tell me how one can apply the ampacity requirement to panel bus. That is, what is the ampacity of panel bus per Code? I'm asking because 215.2 gets right to the matter of conductor ampacity... and Code does not have any provision for panel bus ampacity.

Right, that is what I have a lot of trouble with is how we handle these "310.1 ...integral part of equipment......" conductors. the code needs to give us direction on that. I think either the code should have wording/rewording that says certain things are not feeders, or give us direction on the rules for these feeder conductors that are integral parts of equipment. Perhaps a statement in 215 something like, "this article does not apply to feeder conductors that are integral to equipment." And then an informational note stating, "see article 408 for panelboards, 368 for busways.......etc"

My personal preference would be the former and a rewording of the definition of feeder to read, "....not including conductors that are an integral part of chapter 3 and 4 equipment." And a rewording of 240.21(B) permitting the busing of panelboards, switchboards, and busways to be tapped and allowing the tap to begin at the OCPD load terminals.

Is a circuit breaker a feeder when installed between two feeders?

 

[kwired]

But bus structures that are a part of a panelboard, switchboard, busway... is usually part of a listed unit and that unit usually does have a maximum current rating.

 

[Smart $]

But bus structures that are a part of a panelboard, switchboard, busway... is usually part of a listed unit and that unit usually does have a maximum current rating.

So where are the equipment current rating requirements in Article 215?

All I see are ampacity requirements. Ampacity ratings only apply to wire-type, insulated conductors.

 

[kwired]

So where are the equipment current rating requirements in Article 215?

All I see are ampacity requirements. Ampacity ratings only apply to wire-type, insulated conductors.

If I run a feeder to a junction box and use a splicing/tapping device of some sort to split the feeder in multiple directions, there is no current rating requirement anywhere in Art 215 for the splice/tap device either - yet it just as much a part of the feeder circuit as a panelboard bus isn't it? Or do we have multiple feeders because of this splice/tap - I don't think we do, one overcurrent device ahead of all of it = one feeder IMO.

 

[Smart $]

If I run a feeder to a junction box and use a splicing/tapping device of some sort to split the feeder in multiple directions, there is no current rating requirement anywhere in Art 215 for the splice/tap device either - yet it just as much a part of the feeder circuit as a panelboard bus isn't it? Or do we have multiple feeders because of this splice/tap - I don't think we do, one overcurrent device ahead of all of it = one feeder IMO.

Do these splice/tap devices have an ampacity rating?

Typically, they do not even have a current rating. We rely on wire size and temperature rating, perhaps listing, to determine if they are compliant.

Don't get me wrong. It's a reasonable conclusion. But somewhere in drawing that conclusion you have to make one or more assumptions...

 

[david luchini]

All I see are ampacity requirements.

I see more than just ampacity requirements in Art. 215.

Ampacity ratings only apply to wire-type, insulated conductors.

What Code section says this? And how would 368.17 (B) correspond with this?

 

[Smart $]

I see more than just ampacity requirements in Art. 215.

Yeh... but (in the context of that comment) not regarding conductor current ratings.

What Code section says this?

I infer it from the Ampacity definition. Show me where uninsulated bus (by itself), or any bare conductor for that matter, has a temperature rating in Code.

And how would 368.17 (B) correspond with this?

I say 368.17(A) has it right?"allowable current rating of the busway".

But 368.17(B) was put together by someone(s) that don't understand the proper use of this Code(s) coined word.