Conductor Fill Calculations for typical wiremold

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minesh21

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I'm confused on what NEC section to use when dealing with surface mounted raceways that have receptacles and faceplates (Legrand G4000 wiremold for example). Here are the (3) sections that come to mind:

1. NEC 376 - Metal Wireways: This would be used when it is just a metal wireway with no receptacles or outets (just conductors)
2. NEC 380 - Multioutlet Assemblies: This would be used when you have receptacles and conductors
3. NEC 386 - Surface metal raceways: This would be similar to NEC 376

I'm not sure what the difference is between articles 376 and 386. But I would assume that when dealing with wiremold/plugmold you would apply either article 386 or 380. But while articles 376 and 386 clearly define how to determine conductor fill (20%) and max conductors (30), article 380 doesn't really have any restrictions other than what the manufacturer requires. Is this correct?

Also, it appears that while article 376 limits you to max 20% fill, article 386 will allow you to exceed 20% as long as you apply adjustment factors. Is this correct? I read in the mike holt book for article 386.22 that you must not exceed Table 1, Chapter 9 (which limits you to 40%). So I guess even for article 386 you cannot exceed 40%.

The reason for these questions is that usually we do design involving Legrand G4000 and G6000 raceways and always abide by the standard 20% fill, 30 conductor rules. But if we can apply article 380 instead of 376 or 386 then really we can use what the manufacture indicates (which is 40% fill) and not have to derate. Is this correct? Article 380 doesn't seem to have any restrictions at all...
 
386 would apply to the wiremold raceways you mentioned. Raceways with or without receptacles.

380 is for pre wired assemblies like plugmold, power poles and such.

376 is troughs and like, no receptacles installed.
 
jumper said:
386 would apply to the wiremold raceways you mentioned. Raceways with or without receptacles.

380 is for pre wired assemblies like plugmold, power poles and such.

376 is troughs and like, no receptacles installed.
Click to expand...

Thanks for the response. So Article 380 is only for pre-wired assemblies which is most likely why there aren't any conductor fill requirements.

In regards to Article 386, would you agree that the maximum fill is 40% based on Table 1 Chapter 9?
 
minesh21 said:
Thanks for the response. So Article 380 is only for pre-wired assemblies which is most likely why there aren't any conductor fill requirements.

In regards to Article 386, would you agree that the maximum fill is 40% based on Table 1 Chapter 9?
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The manufactures insrtuctions determine max fill.

386.22 Number of Conductors or Cables. The number of
conductors or cables installed in surface metal raceway
shall not be greater than the number for which the raceway
is designed.
 
jumper said:
The manufactures insrtuctions determine max fill.

386.22 Number of Conductors or Cables. The number of
conductors or cables installed in surface metal raceway
shall not be greater than the number for which the raceway
is designed.
Click to expand...

Ok. Its just that Mike Holt's handbook says to not exceed allowable fill specified in Table 1, Chapter 9. I know this isn't in the code, but I figured this handbook would correctly interpret the code.
 
minesh21 said:
Ok. Its just that Mike Holt's handbook says to not exceed allowable fill specified in Table 1, Chapter 9. I know this isn't in the code, but I figured this handbook would correctly interpret the code.
Click to expand...

IIRC, Legrand publishes the permissible wire fill in it's product brochure. See page 11.
 
minesh21 said:
I'm confused on what NEC section to use when dealing with surface mounted raceways that have receptacles and faceplates (Legrand G4000 wiremold for example). Here are the (3) sections that come to mind:

1. NEC 376 - Metal Wireways: This would be used when it is just a metal wireway with no receptacles or outets (just conductors)
2. NEC 380 - Multioutlet Assemblies: This would be used when you have receptacles and conductors
3. NEC 386 - Surface metal raceways: This would be similar to NEC 376

I'm not sure what the difference is between articles 376 and 386. But I would assume that when dealing with wiremold/plugmold you would apply either article 386 or 380. But while articles 376 and 386 clearly define how to determine conductor fill (20%) and max conductors (30), article 380 doesn't really have any restrictions other than what the manufacturer requires. Is this correct?

Also, it appears that while article 376 limits you to max 20% fill, article 386 will allow you to exceed 20% as long as you apply adjustment factors. Is this correct? I read in the mike holt book for article 386.22 that you must not exceed Table 1, Chapter 9 (which limits you to 40%). So I guess even for article 386 you cannot exceed 40%.

The reason for these questions is that usually we do design involving Legrand G4000 and G6000 raceways and always abide by the standard 20% fill, 30 conductor rules. But if we can apply article 380 instead of 376 or 386 then really we can use what the manufacture indicates (which is 40% fill) and not have to derate. Is this correct? Article 380 doesn't seem to have any restrictions at all...
Click to expand...

One normally has to comply with all parts of the NEC. Most products clearly fit into one and only one article in chapter 3. For example, its clear that EMT falls under 358, and its obvious that articles for PVC or RGS conduit don't apply.

Correct me if I'm wrong, but a mulitoutlet assembly also seems to fit the definition of a surface mounted raceway. If a particular product seems to fit into either of two different articles, do you really get to pick or choose which article to use, or do you have to comply with both?

I'm thinking surface multioutlet assemblies have to comply with both articles 380 and 386.
 
steve66 said:
One normally has to comply with all parts of the NEC. Most products clearly fit into one and only one article in chapter 3. For example, its clear that EMT falls under 358, and its obvious that articles for PVC or RGS conduit don't apply.

Correct me if I'm wrong, but a mulitoutlet assembly also seems to fit the definition of a surface mounted raceway. If a particular product seems to fit into either of two different articles, do you really get to pick or choose which article to use, or do you have to comply with both?

I'm thinking surface multioutlet assemblies have to comply with both articles 380 and 386.
Click to expand...

I did a quick search on plugmold and you are correct. Unlike say the 4000 series data sheet which states article 386, the plug specs cite both articles. Best I could figure out it has to do with which series/type you pick and what you can add.

Some assemblies allow it to be used as a raceway and some did not. There were other configurations also.

I glanced at the UL white book and there were various specs for configurations available/tested.

As far as which article applies, or both, will depend on what all parts get thrown into the mix I guess.

So all in all I have a headache and curse you for bringing up this anomaly.:D
 
jumper said:
I did a quick search on plugmold and you are correct. Unlike say the 4000 series data sheet which states article 386, the plug specs cite both articles. Best I could figure out it has to do with which series/type you pick and what you can add.

Some assemblies allow it to be used as a raceway and some did not. There were other configurations also.

I glanced at the UL white book and there were various specs for configurations available/tested.

As far as which article applies, or both, will depend on what all parts get thrown into the mix I guess.

So all in all I have a headache and curse you for bringing up this anomaly.:D
Click to expand...

Wait the 4000 Series cutsheet calls out both NEC sections on the first page: NEC 380 (Multioutlet) and NEC 386 (Surface Metal Raceway). So if i am using the pre-wired wiremold, I apply NEC 380. If not, use NEC 386???
 
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