Mains conduit fill question (N. America)



That is what I said in the first sentence of my reply.
-- bud--
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bud-- wrote:

I am sorry but the ground wire is also included in the calculations because it too, can carry constant current in cases where protection does not engage. Get your facts correct. The ground wire is just as important of a conductor as any in a race way and is assumed to be able to handle the full current load at 100% duty. If what you say is true, which I know it isn't, we could put pissy small ground wire in the race way, why waste copper. But that isn't the case because it isn't true.
You see, we know a lot about this subject because one of our sister plants once got a citation for insufficient ground wire size and space in a race way due to an accident investigation. The EMT had a short in it but didn't trip the protection down stream. Some one got electrically hurt, not killed but hurt. #6 AWG wires with #8 Ground wire in the pipe with only enough clearance to account for the #6 wires and the ground wire not being of said gauge by code. They got a fine even though it wasn't the cause of the accident. The problem was physical damage caused by a fork truck. Yes, the the fine also included improper guarding of electrical areas and spacing.
The law suit put into place by the person that got injured never fully follow through because about a mouth later, while said injured person was suppose to be home recovering, was driving around and got side railed and killed in an intersection accident. Of course, the person having a alcohol problem I am sure didn't contribute to it.
Now if you want to talk about drain wires we can get on that subject too!
Btw, we manufacture high power wires and cables for a variety of things. However, the power transmission systems in use in our facility isn't any better then the average hack systems you see in most places. The only good wiring that i've seen in house is what our own electricians do for the production machines and offices. THey do follow protocol.
Jamie
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On Fri, 23 Dec 2011 18:40:00 -0500, Jamie

I do not know about the US, butt in the rest of the world, the reason for "wasting" copper in the PE connector is not for carrying nominal current for 100 % of the time, but rather to carry the fault current, which typically is 4-10 times the nominal current. The idea is to insure that the fault current is sufficiently large, in order to _quickly_ burn the fuse or trip other safety device, while keeping the ground potential rise at the faulty device at a safe level.
Even if the phase and neutral wires are thick enough to dissipate the losses at nominal load, at least in Europe, you also have to consider the total loop resistance from the fuse, through the most distant outlet with some extension cords developing a short or ground fault. The fault current must be sufficiently large to rapidly and reliably blow the fuse.
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Jamie wrote:

Nope. For conduit fill, the reason for including the equipment grounding conductor and/or bonding conductor is because they take up space. The computation does not consider current. It is strictly a physical size computation. For example, if you used #10 awg on a 20 amp circuit, your computation has to be based on the 10 awg conductor size, not on the 20 amp breaker.
For computing conductor ampacity derating, the ground or bonding conductors and the neutral conductor that carries only unbalanced current are not required to be counted.
See the NEC code: 310.15(B) (2) (a) (4) and 310.15(B) (2) (a) (5)
Quote: (4) Neutral Conductor. (a)     A neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted when applying the provisions of 310.15(B)(2)(a).
Quote: (5) Grounding or Bonding Conductor. A grounding or bonding conductor shall not be counted when applying the provisions of 310.15(B)(2)(a).
Quote: Table 310.15(B)(2)(a) Adjustment Factors for More Than Three Current-Carrying Conductors in a Raceway or Cable

He has his facts correct. See the NEC code article cited above.

What Bud said is true.

You're wrong.

I suspect that this reveals that you think "derating" as Bud used it means using smaller diameter conductors. That is NOT what derating means.
You must use at least whatever the code requires for the particular circuit - and the code doesn't allow "pissy small" equipment grounding conductors or bonding conductors. I suspect you are using the term "pissy small" to mean too small to safely carry a fault current.
The equipment grounding conductor or bonding conductor is sized to whatever the code requires for the particular circuit. If the conductors will be run in conduit, then the size of the conduit is computed based on the physical size and number of conductors that will be in the conduit.
Ed
<snip>
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Thank you Ed. Jamie should pay attention to Article 250.
?-)
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josephkk wrote:

Guess you've never had to deal with those passing out citations to violations.. They don't care how you, the violator interpret the rules.
I've seen the section that was used to make the citation valid, it was clear and to the point!. You can read all the other side articles you want and hope the one that counts does not get viewed, while your defending yourself. Our lawyers can tell you all about how that one plays out.
I can say with out a doubt, you would never get hired at one of our locations if you claimed to hold an E1 and practice like that.
I'll say no more on the subject, I've said too much already. It's obvious you gamble, and if you do hold a E1, go a head and sign off on those questionable jobs. Just hope no one tells you to start opening up race ways for inspection.
Jamie
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On Sat, 24 Dec 2011 17:22:48 -0500, Jamie

Cite it. We can all read it together.
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You can go through the math and see that there is no need to include the neutral in a total current derating of a conduit. The maximum power transfer without exceeding a current X is when all three phases carry the maximum current, X. In this case, the neutral carries zero current. But what about unbalanced loads? The simplest case is one phase carrying the maximum X and the others zero. In this case the total current is 2X, less than the maximum 3X. If two phases carry the maximum and the other zero, the neutral also carries X and the total is 3X, equal to that from the max load. Any other combination also produces a total current of 3X or less.
There is an exception. Very nonlinear loads like power supplies in computers. They usually draw only during the voltage peak and the neutral current often does not cancel completely. I've heard stories of how the neutral has burned out when supplying a data center full of computers with 3 phase.
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On Fri, 23 Dec 2011 18:40:00 -0500, Jamie

Don't let the actual code language get in the way of a good rant
"(5) Grounding or Bonding Conductor. A grounding or bonding conductor shall not be counted when applying the provisions of 310.15(B)(2)(a)."

I already posted table 250.122 that debunks this myth.
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snipped-for-privacy@aol.com wrote:

Maynard A Philbrook JR, KA1LPA AKA: 'Jamie' is a low grade troll, who tries covering facts with lots of misinformation.
--
You can't have a sense of humor, if you have no sense.

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