more that 3 conductors derating

[Smart $]

If that were relevant, then the code would make us count control wires when we decide whether to derate. But it doesn't. 310.15(B)(2)(a), Exception 1. I can put a 3-phase branch circuit (3-CCCs) in a conduit, and then fill the conduit to 40% with control wires, and not have to derate.

Granted... but the Code does not always match the physics of the phenomena or the level of detail. We could have derating of power conductors by single increment rather than stages... but we don't. And more to the point of this topic, the conductors are not control wires.

The code, as written, does support my viewpoint. :happyyes:

A conductor that cannot carry current because it is physically disconnected, and cannot be connected, is not a CCC. The NEC does not specifically define "current carrying conductor," but I think it fair to say that that term can be defined as a conductor that carries, or that at least has the possibility of carrying, current. I see this situation as being vastly different from having two single-phase circuits, one serving lights and the other receptacles, sharing a conduit. It is physically possible for both the lights and something plugged into the receptacle to be both carrying current at the same time. So even if there is nothing (at the present moment) plugged into the receptacle, the conduit still gets counted as having 4 CCCs. In the present installation, an interlock physically prevents both sets of conductors from being connected at the same time. The ones that are not connected are, by definition of CCC, not CCCs. Therefore, you don't get to read any deeper into the requirements of 310.15(B)(3)(a) than to recognize that the article does not apply because you don't have more than three CCCs.

So whichever side of the coin suits your purpose is the one you use?

I agree with your "not connected" premise. IMO, however, the premise fails for this instance because the conductors are still physically connected to electrical equipment.

Also, the interlock is not adequate justification by itself. What if these conductors powered short-cycle jogging motors, with large starting current, the conductors temperature could potentially reach their thermal limit... yet they were never coincidental loads.

Don't get me wrong. I'm all for not counting conductors as ccc's when they shouldn't be counted. :happyyes:

 

[jumper]

= + =

Daja7,

What is the size and type of the raceway where these 6 conductors
are installed ?

+ = +

1 1/2 and the conductors are #6

Note: for conduit or tubing the size does not matter for derating purposes. 4#12 CCCs in a 4" conduit get derated the same as if the wires were in a 1/2 conduit.

Wireways and stuff have different rules, too lazy to look right now.

 

[jumper]

Please allow me to disagree with everything that has been said so far in this thread. I submit that derating is not necessary in the installation described in the OP.
.

Hey, I thought my post agreed with this opinion!!!:?

 

[Daja7]

Granted... but the Code does not always match the physics of the phenomena or the level of detail. We could have derating of power conductors by single increment rather than stages... but we don't. And more to the point of this topic, the conductors are not control wires.


So whichever side of the coin suits your purpose is the one you use?

I agree with your "not connected" premise. IMO, however, the premise fails for this instance because the conductors are still physically connected to electrical equipment.

Also, the interlock is not adequate justification by itself. What if these conductors powered short-cycle jogging motors, with large starting current, the conductors temperature could potentially reach their thermal limit... yet they were never coincidental loads.

Don't get me wrong. I'm all for not counting conductors as ccc's when they shouldn't be counted. :happyyes:

One of the issues is we can theorize all we want but the code as it is stated is what is. not what could or might be. BTW just got the ruling from AHJ.... not counted as CCC in this case as conductors are electrically and mechanically prevented from operating at the same time. other AHJ's may see it differently.

 

[kwired]

One of the issues is we can theorize all we want but the code as it is stated is what is. not what could or might be. BTW just got the ruling from AHJ.... not counted as CCC in this case as conductors are electrically and mechanically prevented from operating at the same time. other AHJ's may see it differently.

I don't think you mentioned electrically or mechanically prevention from simultaneous operation before. I think most inspectors would allow that as an acceptable way to eliminate the need to count all the conductors as current carrying for deration purposes.

 

[david luchini]

I don't think you mentioned electrically or mechanically prevention from simultaneous operation before.

Well.....Unless you count his Original Post :slaphead:

 

[mwm1752]

FYI -- NEC 2011 Table B.310.15(B)(2)(11) - does address load diversity. Intresting how 4-9 conductors are not part of the astrisk's. Closest NEC article I could find to address conductors carrying current simultaneously.

 

[kwired]

Well.....Unless you count his Original Post :slaphead:

I read OP again before last posting, it didn't mention electrical or mechanical assurance that both loads can not run at same time.

 

[GoldDigger]

I read OP again before last posting, it didn't mention electrical or mechanical assurance that both loads can not run at same time.

[#1] ...they will be alternating via contactors so it will be impossible for both to run at the same time.

This sure looks like electrical or mechanical assurance to me.

 

[kwired]

This sure looks like electrical or mechanical assurance to me.

sorry, missed that part:angel:

 

[charlie b]

So whichever side of the coin (referring to the text in red below) suits your purpose is the one you use?

The NEC does not specifically define "current carrying conductor," . . . The ones that are not connected are, by definition of CCC, not CCCs.

I use the "side of the coin" (i.e., the definition of CCC) that is shown in bold blue text:

. . . but I think it fair to say that that term can be defined as a conductor that carries, or that at least has the possibility of carrying, current.

 

[charlie b]

Hey, I thought my post agreed with this opinion!!!:?

Sorry. I considered your post to be simply providing a copy of a change proposal, rather than offering an opinion of your own. Mea culpa.

 

[GoldDigger]

I use the "side of the coin" (i.e., the definition of CCC) that is shown in bold blue text:

As far as definition and common sense go, we can justify not counting the neutral of a split- or three-phase system from basic principles because any current on the neutral would cause a corresponding decrease in the current in one or more of the phase lines.
But we might not be able to actually avoid counting it were it not for the explicit recognition of that (without explanation) in the Code.

 

[Smart $]

I don't think you mentioned electrically or mechanically prevention from simultaneous operation before. I think most inspectors would allow that as an acceptable way to eliminate the need to count all the conductors as current carrying for deration purposes.

Well.....Unless you count his Original Post :slaphead:

I read OP again before last posting, it didn't mention electrical or mechanical assurance that both loads can not run at same time.

This sure looks like electrical or mechanical assurance to me.

sorry, missed that part:angel:

Interlocked contactors was mentioned but without stating they were mechanically interlocked.

I'm of the opinion one assumes contactors are only electrically interlocked (i.e. via an auxiliary contacts) if mechanical interlocking is not mentioned.

 

[Smart $]

I use the "side of the coin" (i.e., the definition of CCC) that is shown in bold blue text:

. . . but I think it fair to say that that term can be defined as a conductor that carries, or that at least has the possibility of carrying, current.

And that contradicts the latter part of your statement "The ones that are not connected are, by definition of CCC, not CCCs." As I noted, they are still connected to electrical equipment, and as such, "has the possibility of carrying, current." ... and they in fact do, just not concurrently.

 

[GoldDigger]

And that contradicts the latter part of your statement "The ones that are not connected are, by definition of CCC, not CCCs." As I noted, they are still connected to electrical equipment, and as such, "has the possibility of carrying, current." ... and they in fact do, just not concurrently.

The Code needs to be amended to use CCCCC (ConCurrently Current Carrying Conductors.)

 

[kbsparky]

I'll address this point separately: If they get remodeled, it is up to the person doing that work to ensure that the final configuration meets code. We don't design today for what someone will do tomorrow.

Tell that to the folks who mandated that a neutral wire be installed at every wall switch location whether it's needed or not ....

 

[kwired]

Tell that to the folks who mandated that a neutral wire be installed at every wall switch location whether it's needed or not ....

That's all you could come up with?