310.15 (B) (21) wire ampacity

[mbrooke]

Is 310.15 (B) an acceptable means for selecting spacer cable (covered conductor) ampacity?


http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet270


Or should another means like Near McGrath (310.15 C) be applied? Or am I in the wrong place altogether?

 

[Smart $]

For that cable, and assuming over 2000V, I think you want to look at 310.60...

 

[mbrooke]

For that cable, and assuming over 2000V, I think you want to look at 310.60...

Yes, this is over 2000 volts. However the table does not appear to list this particular multi layered type cable?

 

[Smart $]

Yes, this is over 2000 volts. However the table does not appear to list this particular multi layered type cable?

I see.

This has come up before but I forget the resolution, if any. Perhaps just look at it from the temperature limit placed on the termination [110.40]. That usually caps the ampacity anyway.

 

[mbrooke]

I see.

This has come up before but I forget the resolution, if any. Perhaps just look at it from the temperature limit placed on the termination [110.40]. That usually caps the ampacity anyway.

The terminals are rated at least 90*C, but the conductor can not go over 75*C continuous as it can damage the covering.

Question for the curious. Why does 310. B 21 exist when tables 310.60 and onward technically have you covered?

 

[Smart $]

The terminals are rated at least 90*C, but the conductor can not go over 75*C continuous as it can damage the covering.

With the conductors being covered and the covering not recognized by Code as electrical insulation, that's a design issue.

Question for the curious. Why does 310. B 21 exist when tables 310.60 and onward technically have you covered?

Up to 2000V considerations, perhaps.

???

 

[mbrooke]

With the conductors being covered and the covering not recognized by Code as electrical insulation, that's a design issue.

I disagree (humbly), it would point me to 310.15 B 21 because it specifically says "covered"

Up to 2000V considerations, perhaps.

???

Maybe. Above 600 volts you have "bare", "covered" and "insulated"

 

[Smart $]

I disagree (humbly), it would point me to 310.15 B 21 because it specifically says "covered"

Maybe. Above 600 volts you have "bare", "covered" and "insulated"

Remind me... what is the title of 310.15?

 

[mbrooke]

Remind me... what is the title of 310.15?

This:

Table 310.15(B)(21) (formerly Table 310.21) Ampacities of Bare or Covered Conductors in Free Air, Based on 40°C (104°F)
Ambient, 80°C (176°F) Total Conductor Temperature, 610 mm/sec (2 ft/sec) Wind Velocity

 

[Smart $]

This:

I said the title of 310.15... this:

310.15 Ampacities for Conductors Rated 0–2000 Volts.

All contents therein are subject to the limitations noted in the title... and Table 310.15(B)(21) is a part thereof.




.

 

[mbrooke]

I said the title of 310.15... this:

All contents therein are subject to the limitations noted in the title... and Table 310.15(B)(21) is a part thereof.




.

Oh! :ashamed1: My mistake :slaphead:

Then you would be correct.

 

[Julius Right]

I think you are right. NEC does not recognize the covered cable as medium voltage cable since it is not shielded as per NEC art.10(E) Shielding and not constructed as per UL1072 [indicated in Informative Annex A Product Safety Standards.]
You cannot use it as a MV cable in no way.
As indicated in Southwire catalogue:
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet85
"Used primarily for, but not limited to, overhead secondary distribution lines. Installed on insulators, otherwise treated as a bare conductor."
Ampacity may be considered as per Table 310.15(B) 21 never the less there is no indication of the covering material [pvc,xlpe,HDPE or else] and thickness, neither ANSI/ICEA S-70-547 is mentioned. The ambient is 40oC.
According to NEC the temperature is limited to 80oC and in the manufacturer catalogue only 75oC [even XLPE insulation-90oC rated- is employed] and the ambient is 25oC.