I am more of a controls guy and do not use the NEC as often as many of you, nor do I have the same interpretation skills of the code. But I have found that in our facility we have a dept. being fed by 480V 3Ph service to a fused disconnect (100A fuses). This feed supplies several similiar machines that each contain a 10A fused disconnect in the control panel. The conductors leaving the 100A disconect are 12Awg. This is not to code based on the way I interperet 240-3. However, I am a little confused about the 10'and 25' tap rule. The machinery being supplied is in excess of 25' from the 100A fused disconnect and is in 1" EMT. Any help is greatly appreciated. This forum is very informative and I enjoy reading many of the Q&A's.
Conductor Over-current Protection
- Thread starter todd99
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Senior Member
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- New York, 40.7514,-73.9925
Re: Conductor Over-current Protection
If it is not in compliance with the tap rules, what you describe seems like a code violation.
If it is not in compliance with the tap rules, what you describe seems like a code violation.
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- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: Conductor Over-current Protection
It appears that you are dealing with the 1999 code.
Help me understand something. The ?Tap Rules? are for feeders. This situation is one that involves branch circuits. I cannot see anything that allows a branch circuit for a machine to be protected at a value above its ampacity (except it can go to the next higher standard setting). I don?t see any way to have a 100 amp disconnect ahead of #12 conductors, regardless of what the Tap Rules say, because these are branch circuits. I think you have a violation of 210-20.
It appears that you are dealing with the 1999 code.
Help me understand something. The ?Tap Rules? are for feeders. This situation is one that involves branch circuits. I cannot see anything that allows a branch circuit for a machine to be protected at a value above its ampacity (except it can go to the next higher standard setting). I don?t see any way to have a 100 amp disconnect ahead of #12 conductors, regardless of what the Tap Rules say, because these are branch circuits. I think you have a violation of 210-20.
- Location
- Massachusetts
Re: Conductor Over-current Protection
These are feeder taps.
These are feeder taps.
That said they are not legal feeder taps.
Re: Conductor Over-current Protection
If the 10A fused disconnect is internal to the equipment, aren't the conductors then branch circuit conductors? Adding a fuse to a light fixture doesn't change the branch circuit to a feeder.
If it is then a branch circuit, 210.19(4) seems to allow this. (This rule confuses me: the excpetions seem to be more strict than the rule.) Then the 100A branch circuit is allowed by 210.23(D).
I am assuming the "equipment" is not listed in table 210.2.
Steve
If the 10A fused disconnect is internal to the equipment, aren't the conductors then branch circuit conductors? Adding a fuse to a light fixture doesn't change the branch circuit to a feeder.
If it is then a branch circuit, 210.19(4) seems to allow this. (This rule confuses me: the excpetions seem to be more strict than the rule.) Then the 100A branch circuit is allowed by 210.23(D).
I am assuming the "equipment" is not listed in table 210.2.
Steve
ryan_618
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- Salt Lake City, Utah
Re: Conductor Over-current Protection
The difference to me is whether the fuse is an overcurrent device or a supplemental overcurrent device.
Re: Conductor Over-current Protection
Ryan:
Can you define "supplemental overcurrent device"? Would it be a device that is not required by code?
If thats the case, then I assume you mean if the device is supplemental, then the conductors are branch circuit conductors. If the device is not supplemental, then the conductors are feeders.
Steve
Ryan:
Can you define "supplemental overcurrent device"? Would it be a device that is not required by code?
If thats the case, then I assume you mean if the device is supplemental, then the conductors are branch circuit conductors. If the device is not supplemental, then the conductors are feeders.
Steve
ryan_618
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- Salt Lake City, Utah
Re: Conductor Over-current Protection
Hi Steve. If you have the 2005, it is actually defined in art 100 (or perhaps 240, I don't recall). I don;t have my 05 at work, so I can't quote verbatum, but a fuse in a light is basically what they are talking about with supplementary overcurrent protection.
As far as your thoughts go, you are correct regarding feeder vs. branch circuit.
Hi Steve. If you have the 2005, it is actually defined in art 100 (or perhaps 240, I don't recall). I don;t have my 05 at work, so I can't quote verbatum, but a fuse in a light is basically what they are talking about with supplementary overcurrent protection.
As far as your thoughts go, you are correct regarding feeder vs. branch circuit.
petersonra
Senior Member
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- Northern illinois
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- Semi-retired engineer
Re: Conductor Over-current Protection
generally, I think you can say that supplemental OCD are there to protect a specific device, as opposed to a branch circuit protector which protects the premises wiring. Supplemental protection is also commonly used as a means of shutting off power to individual devices so they can be serviced without having to shut off everything else on the same branch circuit.
Re: Conductor Over-current Protection
I don't have the 2005 code yet. Using the definition provided by petersonra, I think the disconnects on the equipment are probably supplementary.
I think that makes these taps branch circuits. And (if I understand 210.19(4)), I think they are allowed.
Steve
I don't have the 2005 code yet. Using the definition provided by petersonra, I think the disconnects on the equipment are probably supplementary.
I think that makes these taps branch circuits. And (if I understand 210.19(4)), I think they are allowed.
Steve
ryan_618
Senior Member
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- Salt Lake City, Utah
Re: Conductor Over-current Protection
Steve: Here is the 2005 definition:
Steve: Here is the 2005 definition:
Re: Conductor Over-current Protection
Thanks Ryan.
Do you then think these taps are allowed?
Or do I misunderstand 210.19(4)? Like I said, this article confuses me because the exceptions seem more restrictive than the rule. So can I read the rule and ignore the exception, or do I have to make sure all the exceptions allow this also??
Steve
Thanks Ryan.
Do you then think these taps are allowed?
Or do I misunderstand 210.19(4)? Like I said, this article confuses me because the exceptions seem more restrictive than the rule. So can I read the rule and ignore the exception, or do I have to make sure all the exceptions allow this also??
Steve
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Conductor Over-current Protection
Steve: I think if you read the rule and ignore the exception it is not a legal tap, and therefore you would have a hard time satisfying 240.4(D), because that would require the line side OCPD to be not more than 20 amps. 210.19(4) discusses the size of the conductors, but it does not address the manner in which they are protected (like the exceptions do). Becasue of this, we must read this rule to learn how to size the conductors, then continue in article 210 [210.20(B)] to learn how we protect these conductors. Once we get to 210.20, we find that we must then comply with 240.4, in particluar, 240.4(D)
That is the way I read it anyway. Anyone else??? Please???
[ September 30, 2004, 12:17 PM: Message edited by: ryan_618 ]
Steve: I think if you read the rule and ignore the exception it is not a legal tap, and therefore you would have a hard time satisfying 240.4(D), because that would require the line side OCPD to be not more than 20 amps. 210.19(4) discusses the size of the conductors, but it does not address the manner in which they are protected (like the exceptions do). Becasue of this, we must read this rule to learn how to size the conductors, then continue in article 210 [210.20(B)] to learn how we protect these conductors. Once we get to 210.20, we find that we must then comply with 240.4, in particluar, 240.4(D)
That is the way I read it anyway. Anyone else??? Please???
[ September 30, 2004, 12:17 PM: Message edited by: ryan_618 ]
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