Feeder size

[Toros]

Hi
i have to feed an apartment sub panel with 83 A load per calc. with #3 conductor that I selected

1) Somebody says that I have to use 75 deg. column in 310.15 b16 if terminals are @ 75deg.

2) But, 110.14 c1 says, use 60 deg. for conductors #1 or smaller (the one I chose)

3) on the other hand, some says that I have to use 310.15 b7 in this situation.

I am confused here?????

tanx

 

[charlie b]

First, the easy one: your item #3. You never have to use 310.15(B)(7). It is worded in the sense of "shall be permitted." In this case, however, if this panel really is a "sub-panel," meaning that it does not supply 100% of the loads for the entire apartment, then this article cannot be used.

Regarding your item #1, the "somebody" who says that is 110.14(C).

Regarding your item #2, you need to read further down, specifically to 110.14(C)(1)(a)(3). It is a bit confusing, but that is what allows you to use the 75C column for circuits under 100 amps, provided the "equipment" (i.e., the terminations) are listed for this use (i.e., are listed for 75C).

Now please clear up a point for me. Are you using aluminum wire? If so, then #3 AWG is not going to be adequate.

 

[david luchini]

Hi
i have to feed an apartment sub panel with 83 A load per calc. with #3 conductor that I selected

1) Somebody says that I have to use 75 deg. column in 310.15 b16 if terminals are @ 75deg.

2) But, 110.14 c1 says, use 60 deg. for conductors #1 or smaller (the one I chose)

3) on the other hand, some says that I have to use 310.15 b7 in this situation.

I am confused here?????

tanx

1) You are permitted, but not required, to use the 75 deg column if your terminals are 75deg. Using the 60deg column gets you a larger conductor size.

2) 110.14(C)(1)(a)(3) permits conductors with a higher temperature rating when the equipment is listed and identified for use with those conductors.

3) You are permitted, but not required, to use 310.15(B)(7) if you meet the requirements of that section.

 

[Dennis Alwon]

Hi
i have to feed an apartment sub panel with 83 A load per calc. with #3 conductor that I selected

1) Somebody says that I have to use 75 deg. column in 310.15 b16 if terminals are @ 75deg.

2) But, 110.14 c1 says, use 60 deg. for conductors #1 or smaller (the one I chose)

3) on the other hand, some says that I have to use 310.15 b7 in this situation.

I am confused here?????

tanx

I guess you didn't trust my response.

 

[Dennis Alwon]

You don't have to use 310.15(B)(7) however it allows a smaller size if you meet the requirements as David stated. In the 2011 code the question of 75C doesn't even enter into the equation with T. 310.15(B)(7) however it probably should as the 2014 NEC changed that section to accommodate other de-rating factors.

If you are using NM cable then you cannot use that Table and you would have to use the 60C column

 

[iceworm]

1) Somebody says that I have to use 75 deg. column in 310.15 b16 if terminals are @ 75deg.

2) But, 110.14 c1 says, use 60 deg. for conductors #1 or smaller (the one I chose)

Adding to all of the other excellent information

Toros -
Just as a practical matter: I haven't seen a 60C CB in maybe 20 years. 60C/75C - yes. 75C - yes. 60C - no. Highly recommend looking at the CB. Or, if the CB is not available, look up the specs.

Now if the wire is 60C you must use 60C column - doesn't matter what the CB says. Highly recommend looking at the wire spec. Other than NM and derivates, 60C wire has not been common for 20 years either.

ice

 

[Dennis Alwon]

Other than NM and derivates, 60C wire has not been common for 20 years either.

ice

NM has 90C conductors but we must use the 60C column because the nec states this in art. 334 We can use the 90C for de-rating but the final overcurrent protective device must be based on 60C when using nm cable

 

[augie47]

I guess you didn't trust my response.

obviously a wise man

NM has 90C conductors but we must use the 60C column because the nec states this in art. 334 We can use the 90C for de-rating but the final overcurrent protective device must be based on 60C when using nm cable

and in some case, SE can be limited to 60? also.

 

[Toros]

First, the easy one: your item #3. You never have to use 310.15(B)(7). It is worded in the sense of "shall be permitted." In this case, however, if this panel really is a "sub-panel," meaning that it does not supply 100% of the loads for the entire apartment, then this article cannot be used.

Regarding your item #1, the "somebody" who says that is 110.14(C).

Regarding your item #2, you need to read further down, specifically to 110.14(C)(1)(a)(3). It is a bit confusing, but that is what allows you to use the 75C column for circuits under 100 amps, provided the "equipment" (i.e., the terminations) are listed for this use (i.e., are listed for 75C).

Now please clear up a point for me. Are you using aluminum wire? If so, then #3 AWG is not going to be adequate.

i am using copper

 

[Toros]

1) You are permitted, but not required, to use the 75 deg column if your terminals are 75deg. Using the 60deg column gets you a larger conductor size.

2) 110.14(C)(1)(a)(3) permits conductors with a higher temperature rating when the equipment is listed and identified for use with those conductors.

3) You are permitted, but not required, to use 310.15(B)(7) if you meet the requirements of that section.

Back to item#3,
Does 110.14 say that Ivan use this if feeding builds entire load
this is an apaartment
so, disregarding 21.15 about 75 deg., I can use 310-.15b7

 

[augie47]

Look closely at 310.15(B)(7) including the header,,,,,
Is it a 120/240 volt single-phase 3 wire feeder ?
Are you using one of the wire types listed in the Table ?
If so you can use it for the individual dwelling unit, not for the complex.