Cord question

[derekleffew]

In a recent discussion, member @JD linked to this cord:

CEP All-Weather Power Cord — 50-Ft., 50 Amps, 240 Volts, Model# 6450M | Generator Cordsets Plugs| Northern Tool + Equipment

What I find peculiar is that the jacket reads

Carol 6/3 & 8/1 90°C SOW ...

which we know means three [HASHTAG]#6[/HASHTAG] AWG and one [HASHTAG]#8[/HASHTAG] conductor(s).
WHY would a cable have two different sized conductors?
Is there some NFPA code or listed, by NRTL that allows (or requires) this?

I know school is supposed to be over for the summer, but one never stops (or at least should never stop) learning. Students only, for one week please.

 

[zmb]

Typically a large conductor or multiples are seen on the neutral line of dimmer rack due to harmonics that would cause the current to exceed what it was sized for.

Presuming that this cord is for 120/240 split phase, what's coming into most houses, the 8 gauge conductor is smaller then the rest and going to be for the ground connection. Cannot cite a code listing for why this would be allowed, but certainly reduces costs with less copper.

 

[derekleffew]

Anyone care to agree/disagree with @zmb ? Extra points awarded for the proper code citation.

Let's assume he is correct. Can the savings of using one [HASHTAG]#8[/HASHTAG] wire over [HASHTAG]#6[/HASHTAG] offset the added complexity of manufacturing a cable with different sized conductors inside?

 

[gafftapegreenia]

I know I asked about this once in a different thread. It was about a set of banded feeder I once worked with on a photo shoot. @STEVETERRY gave me an answer, I'll see if I can find it.

I didn't realize they manufactured cable with a smaller ground wire than the current carrying conductors, but it its allowable in banded feeder, why not in a cable assembly?

 

[zmb]

Let's assume he is correct. Can the savings of using one #8 wire over #6 offset the added complexity of manufacturing a cable with different sized conductors inside?

That's the question I have too. Has to complicate the machinery that winds everything neatly together, which adds cost. Probably more economical on longer cables with large conductors.

 

[JD]

I find it perplexing as I can't image that much is saved. Yes, it is the ground conductor that is #8. For what they charge, you could buy 6/4 and put the connectors on and still save money.

They charge $600 for the 100 foot one. 100' of 6/4 SOOW goes for about $400. Add the connectors and you still save over $100.

 

[BillConnerFASTC]

One sage in this industry was quite clear that every penny in parts to the manufacturer is a dollar at retail.

As far as building your own saving, that would have to include the value of your time and the cost of assuming the liability in addition to just the cost of the parts. Heck, if I was making just one, I could spend more than an hour sourcing the parts, but ymmv.

 

[JChenault]

I'm missing something.

The cable has four conductors

The plugs look to me as if they have only three lugs.

Huh?

 

[sk8rsdad]

The outer shell is the ground.

 

[MarfaLights]

The outer part of the connector is metal and grounded.

 

[headcrab]

NEC 2011 250.122 (A) Copper...equipment grounding conductors...shall not be smaller than shown in Table 250.122....

Which says that if the OCPD does not exceed 60A, the ground conductor may be 10AWG or larger. We can use column B in Table 400.5 to determine that the 6AWG conductors will carry 55A. Thus the ground conductor could actually be smaller.

Someone tell me if I'm wrong.

 

[porkchop]

The outer part of the connector is metal and grounded.

I wouldn't say the outer part of the connector is metal. It looks like there is a 4th contact that is meant to be a grounding conductor on the outer rim, but I'd bet the outer parts of the connector (and probably the whole connector minus the contacts for that matter) are plastic.

PS: Good question Derek.

 

[STEVETERRY]

NEC 2011 250.122 (A) Copper...equipment grounding conductors...shall not be smaller than shown in Table 250.122....

Which says that if the OCPD does not exceed 60A, the ground conductor may be 10AWG or larger. We can use column B in Table 400.5 to determine that the 6AWG conductors will carry 55A. Thus the ground conductor could actually be smaller.

Someone tell me if I'm wrong.

You are correct.

ST

 

[garyvp]

However, for SCR dimmer circuits the neutral has to be larger than the phase conductors - see NEC 220.61 and 310.15(B)(4)(c) regarding non-linear loads/harmonic loads. Conventional 50 amp cables are 2x#6 and 2x#8 - not meant for dimmers. Agree with JD..minimally you should make your own 50 amp cable out of 6/4.

 

[STEVETERRY]

However, for SCR dimmer circuits the neutral has to be larger than the phase conductors - see NEC 220.61 and 310.15(B)(4)(c) regarding non-linear loads/harmonic loads. Conventional 50 amp cables are 2x#6 and 2x#8 - not meant for dimmers. Agree with JD..minimally you should make your own 50 amp cable out of 6/4.

However, for SCR dimmer circuits the neutral has to be larger than the phase conductors - see NEC 220.61 and 310.15(B)(4)(c) regarding non-linear loads/harmonic loads. Conventional 50 amp cables are 2x#6 and 2x#8 - not meant for dimmers. Agree with JD..minimally you should make your own 50 amp cable out of 6/4.

Err...not exactly. The only time a neutral conductor must be larger than the phase conductors when feeding nonlinear loads is when using portable single conductor feeders, per 520.53(O)(2). This is because the ampacity tables for portable single conductor cables are based on the free-air rating of the cables, so there is no ampacity overhead.

In all other cases like multiconductor cables feeding nonlinear loads, the neutral must simply be considered a current carrying conductor, which has the effect of derating the ampacity of all phase conductors as well as the neutral, per section 400.5.

ST

 

[BillESC]

The smaller conductor just doesn't save copper. The diameter of the cable will be less requiring less jacket. This smaller diameter will wind tighter requiring smaller reels or allow more footage on existing reels. It will also weigh less per foot and when shipping tens or hundreds of thousands of feet will result in reduced freight costs.

The saving on a consumers 100' are next to nothing but for the manufacturers annual production run they would be significant.

 

[garyvp]

Err...not exactly. The only time a neutral conductor must be larger than the phase conductors when feeding nonlinear loads is when using portable single conductor feeders, per 520.53(O)(2). This is because the ampacity tables for portable single conductor cables are based on the free-air rating of the cables, so there is no ampacity overhead.

In all other cases like multiconductor cables feeding nonlinear loads, the neutral must simply be considered a current carrying conductor, which has the effect of derating the ampacity of all phase conductors as well as the neutral, per section 400.5.

ST

Interesting distinction....learn something new every day.