310.15(b)(1)(1) vs 310.15(b)(1)(2)

[Ponchik]

Besides one is for 86F and one is 104F what is the difference between the two tables? 310.15(b)(1)(1) vs 310.15(b)(1)(2)?

I have always used the 86F table. When is the 104F table used?

TIA

 

[david luchini]

Different conductor types.

See, for instance, T310.18 for conductors that would use 310.15(b)(1)(2).

 

[Deltaforce]

Besides one is for 86F and one is 104F what is the difference between the two tables? 310.15(b)(1)(1) vs 310.15(b)(1)(2)?

I have always used the 86F table. When is the 104F table used?

TIA

104F table outdoor application, free air,
single insulated cables
The two tables give different final ampacities, So not mix up

 

[ramsy]

have always used the 86F table. When is the 104F table used?

Always preferred equation 310.15(B), for a wider range of equipment, and conditions than idiot tables, and simple enough for a spreadsheet.

 

[Ponchik]

Got it. Thanks you.

I had never noticed the note under each of the tables.

 

[david luchini]

104F table outdoor application, free air,
single insulated cables
The two tables give different final ampacities, So not mix up

This is not correct.

T310.17 is for "single insulated conductors in free air" and would use the 86F Table.

T310.18 is for "not more than 3 conductors in raceway or cable", and would use the 104F table.

 

[Deltaforce]

This is not correct.

T310.17 is for "single insulated conductors in free air" and would use the 86F Table.

T310.18 is for "not more than 3 conductors in raceway or cable", and would use the 104F table.

Correct, but my point if T310.17 used without 104F correction factor, final ampacity not same as when 104F table used directly (correction factor =1)

 

[david luchini]

Correct, but my point if T310.17 used without 104F correction factor, final ampacity not same as when 104F table used directly (correction factor =1)

I would think your point should be T310.17 CANNOT be used with the 104F correction factor table.

 

[Deltaforce]

I would think your point should be T310.17 CANNOT be used with the 104F correction factor table.

Are you saying T310.17 should used base ambient temperature of 30C only?

 

[david luchini]

Are you saying T310.17 should used base ambient temperature of 30C only?

Yes. 310.17 tells you it is for for conductors installed in a 30C ambient.

 

[Deltaforce]

Yes. 310.17 tells you it is for for conductors installed in a 30C ambient.

So if ambient temperature 40C, T310.17 not use, even though temperature correction factors for 40C ambient temperature available in code?

 

[david luchini]

So if ambient temperature 40C, T310.17 not use, even though temperature correction factors for 40C ambient temperature available in code?

i don't understand what you are asking.

 

[Deltaforce]

i don't understand what you are asking.

I ask why you not want apply 40C correction factor to T310.17 when ambient temperature 40C

 

[david luchini]

I ask why you not want apply 40C correction factor to T310.17 when ambient temperature 40C

You DO apply a correction factor for an ampacity from T310.17 when the ambient isn't 30C.

 

[Deltaforce]

You DO apply a correction factor for an ampacity from T310.17 when the ambient isn't 30C.

But you said:

I would think your point should be T310.17 CANNOT be used with the 104F correction factor table.

 

[david luchini]

But you said:

Yes...that's correct. It has to be used with the 86F correction factor table.

 

[david luchini]

But you said:

Maybe this will help...

#1 awg THWN has an ampacity of 195 in T310.17.

In a 40C ambient, the ampacity will be 171.6.

 

[Deltaforce]

Maybe this will help...

#1 awg THWN has an ampacity of 195 in T310.17.

In a 40C ambient, the ampacity will be 171.6.

What it ampacity in T310.19?

 

[david luchini]

What it ampacity in T310.19?

#1 THWN doesn't have an ampacity in T310.19.

 

[Deltaforce]

#1 THWN doesn't have an ampacity in T310.19.

Well, more clarity, this question:
Two outdoor installations. Both single insulated, same size cable in free air. But one ampacity on base 30C ambient and other 40C base ambient. Ampacity of each cable?