Article 240?

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john mac donald

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Hi Mike,
I wonder if you can answer this question and settle an argument?? In a downtown high-rise building in which we are doing a tenant fit-out, there are three 100A MLO panelboards each fed with 4#2 AWG from a single 100A fused disconnect switch thru a junction box. Inside the junction box, the three panel feeders are spliced to the incoming feeder from the 100A fused disconnect switch.

Could any of these panel feeders be considered a tap under any of the rules of Article 240 of the NEC or is this simply a tee splice? Are there any code restrictions on this application?

A tap is usually considered to be a smaller conductor than the feeder conductor. In this case there is no reduction of the feeder size, therefore it does not constitute a tap.

Your thoughts would be appreciated..
 
Re: Article 240?

Mike does not often post replies on this Forum. But there are many others who do.

I lost a discussion (I'll not call it an argument) on a similar situation. I lost it when the other party quoted the definition of "tap conductors" from 240.2. All of the conductors you have described are protected at 100 amps, and their ampacity is 115 amps. You do not have "tap conductors."
 
Re: Article 240?

you are gonna use 100 amps up fast filling out three panels. you still have the problem with total connected load at the first disconnect.
 
Re: Article 240?

Since the conductors from the first disconnect to the j-box will supply the three 100 amp panels, I suspect there may be a violation of 215.2(A)(1)
 
Re: Article 240?

OK,here is my first attempt at a post for a question.I don't see the violation,my book is in my truck.But,I would buy 100A fuses in bulk it is cheaper that way.
 
Re: Article 240?

Originally posted by Awg-Dawg:
OK,here is my first attempt at a post for a question.I don't see the violation,my book is in my truck.But,I would buy 100A fuses in bulk it is cheaper that way.
Click to expand...
215.2(A)(1) requires the conductors to have an ampacity not less than the calulated load that they supply. #2 copper at 75? has an ampacity of 115 amps. I am just saying that since the conductors from the first disconnect to the j-box supply three 100 amp panels, I suspect the calculated load will exceed 115 amps. We can't be sure without knowing the calculated load.
 
Re: Article 240?

eprice has got it right. The conductors are feeders and they must be of the appropriate size based on the calculation requirements in
Article 220.
 
Re: Article 240?

The original question was not about whether the cables were adequately sized for the load. The question had to do with whether the tap rules applied, and whether there was any rule against the type of connection being described. I think the answers are both "no." But as to whether the cables are large enough, I agree that you need a load calculation to answer that question.
 
Re: Article 240?

The original question included this

Originally posted by john mac donald:
Could any of these panel feeders be considered a tap under any of the rules of Article 240 of the NEC or is this simply a tee splice? Are there any code restrictions on this application?
Click to expand...
And that is what I have been responding to.

[ November 23, 2005, 11:24 AM: Message edited by: eprice ]
 
Re: Article 240?

While I am new at this site, I certainly appreciate the quick response to this inquiry on the NEC, and the expertise of the respondents. I agree that feeder loading is a prime consideration in this type of application. I can only assume that it was used for reasons of space and circuit breaker availability where loading was minimal. It is not a design that I would recommend, but the replies settled the argument here as to whether this was a tap or a feeder. Thanks to all, and I will look forward to visiting your web site again.
 
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