(4)Neutral conductor

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RUWired

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will the neutral conductor be counted as a c.c.c. on a 3 phase 4-wire (120/208v) feeder when the building contains computors and electronic ballast for lighting?Is this the only consideration?
Rick
 
In my opinion that is a very tough question to answer.

316.15(B)(4)(c)On a 4-wire, 3-phase wye circuit where the major portion of the load consists of nonlinear loads, harmonic currents are present in the neutral conductor; the neutral shall therefore be considered a current-carrying conductor.
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What is a 'major portion of the load'?

IMHO opinion a major portion of anything is at least 75%

But who's to say it's not 50.01%?
 
So if i look at loads in the building and find that maybe the electric heating and ac loads are larger, i might be fine.
Rick
 
2cnts

2cnts

.

NEC and all AIA's EE's are suggesting/mandating "up sizing" in advance.

The OP IMO is reverse thinking not forward. Wouldnt fly in my zip code.
 
My 2 cents says that anything above 50% is a major portion. If you look at the Congress of the USA the majority leader is from a party with more than 50%. The minority leader would be from the party with less than 50%.
 
infinity said:
My 2 cents says that anything above 50% is a major portion. If you look at the Congress of the USA the majority leader is from a party with more than 50%. The minority leader would be from the party with less than 50%.
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I see what your saying but note that the majority leader is not the Major Majority leader.

They put the word 'major' in their for a reason.

But I agree it is certainly up for debate. :)

If we are taking about a building service I doubt that the non-linear loads approach 30%.

If we are talking about a feeder to IT equipment than that is another mater altogether.
 
if this building had higher hvac loads when running,and non-linear loads when off, i'd have to count it.
Rick
 
Rick you called it a feeder but it sounds like a service.

The 'major' portion of the load on a service is fictitious Article 220 requirements.

It certainly will not hurt anything to call the neutral a current carrying condutor....other than the costs.
 
iwire said:
What woudn't fly?

If the buildings load is 45% non-linear and 55% linear it has to fly.
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Bob, Im my zip, the "big fish" have all read the writing on the wall with regards
to the "harmonic" issue. So has the NEC. AND so I have.

You cant treat a "building" without regards to future expansion

In my zip the GC/Neutral is the big issue. No one cares about allowing a minimum. Thats backward thinking.
 
Actually ,it is 1 of 3 feeders to a building from a service and all the feeder loads will be the same.I was trying to keep the conductor sizes to a minimum.Looks like i will have to upsize one for derating.
Rick
 
Gmack as this is an NEC forum I tend to give answers based on the NEC, not design issues.

Gmack said:
Bob, Im my zip, the "big fish" have all read the writing on the wall with regards
to the "harmonic" issue. So has the NEC. AND so I have.
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Who are the big fish and just what would this writing be?

You cant treat a "building" without regards to future expansion
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Actually following the NEC yes you can design a building without regards to future use. And if that is what the person paying the bill wants than it is the right thing to do.

In my zip the GC/Neutral is the big issue. No one cares about allowing a minimum. Thats backward thinking.
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What is backward about giving a factual answer to a code question?

As we know very little (almost nothing) about the installation we can not assume the neutral should be code minimum or not.
 
NEC and all AIA's EE's are suggesting/mandating "up sizing" in advance.
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I'm not familiar with this suggestion or the mandating the increase in size of the neutral by the NEC and EE's. Where could I find more information?
Harmonics from computer/server power supplies are becoming less of a problem as new equipment is compliant with European harmonic limits and have power factor correction, which in the method they use results in less harmonics sent upstream.
 
O.K., So I'll start over with my question.I will be feeding three 400 amp main breaker panels from an outdoor service. Each of these panels have combinations of loads,Lighting-recpt.,hvac,computors on the network.Will the neutral in this case be a c.c.c.?
Rick
 
gmack,
Bob, Im my zip, the "big fish" have all read the writing on the wall with regards to the "harmonic" issue. So has the NEC. AND so I have.
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I have talked with a number of engineers who design office buildings and they don't do anything special for the nonlinear loads and their buildings never have any problems. Also I find it very interesting that almost all of the information on this "problem" is authored by someone who works for a manufacturer that has an economic interest in correcting the "problem".
Don
 
RUWired said:
O.K., So I'll start over with my question.I will be feeding three 400 amp main breaker panels from an outdoor service. Each of these panels have combinations of loads,Lighting-recpt.,hvac,computors on the network.Will the neutral in this case be a c.c.c.?
Rick
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Unless you have more than 200 amps of nonlinear loads on any one feeder, the neutral is NOT counted as current carrying conductor.

(Although there may be differences of opinion on what a "Majority" is, I think we can all agree that less than half is not a majority.)

Steve
 
NEC Article 90

NEC Article 90

(B) Adequacy This Code contains provisions that are considered necessary for safety. Compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.

FPN: Hazards often occur because of overloading of wiring systems by methods or usage not in conformity with this Code. This occurs because initial wiring did not provide for increases in the use of electricity. An initial adequate installation and reasonable provisions for system changes provide for future increases in the use of electricity.

2005 Commentary:

Consideration should always be given to future expansion of the electrical system. Future expansion might be unlikely in some occupancies, but for others it is wise to plan an initial installation comprised of service-entrance conductors and equipment, feeder conductors, and panelboards that allows for future additions, alterations, designs, and so on.

Take a look also at:

http://ecmweb.com/mag/electric_case_soontobe_overloaded/index.html
 
You of course understand that a FPN suggestion is not a requirement and that Handbook commentary is also not a requirement.

Separate what are code minimums from good design.

I happen to exceed code minimums on a daily basis like many of the members here. That aside it is always with in our rights to wire only to code minimums.

It is really up to the person paying for the work to decide how much they want to spend today to save them money in the future.
 
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