Cap.

[Flight987]

What is the minimum size THW,or THHN conductor that can be used to wire an 80 kvr,3/0 460 volt Cap.
Help me on this one . Mike doesn't have anything in the work book.

 

[infinity]

Capacitors are covered in Article 460.

 

[jumper]

What is the minimum size THW,or THHN conductor that can be used to wire an 80 kvr,3/0 460 volt Cap.
Help me on this one . Mike doesn't have anything in the work book.

Is this correct? kVA? 3/0?

 

[infinity]

Is this correct? kVA? 3/0?

How about 3 ??

 

[jumper]

How about 3 ??

thanks.

Now if OP will make sure if it is 80 kVA....

 

[Flight987]

Key Say's

Key Say's

Key say's 1/0, Ref. 460.8

 

[jumper]

Key say's 1/0, Ref. 460.8

that is what I got.

Start by converting 80kVA to amps

 

[infinity]

Try this formula to find the current then use the reference 460.8 to find the minimum conductor ampacity.

I=kva/(E * 1.73)

 

[Flight987]

I don't think so

I don't think so

Is this correct? kVA? 3/0?

Test key say's 1/0, But I don't know , that is I am asking.

 

[jumper]

Test key say's 1/0, But I don't know , that is I am asking.

What you have is cap for a 80kVA load. Supply voltage 480V 3 phase. Start by converting kVA to amps.

 

[Hv&Lv]

that is what I got.

Start by converting 80kVA to amps

I do either POCO calcs. or residential only.
The POCO calcs are a little different that NEC calcs. With that said, I want to see if I can get this right. Jumper, 135.7? Which comes out to 1/0. (75?) Yes or try again...

 

[Flight987]

I Did some Cal.

I Did some Cal.

I took 80000/(460x1.732 =796.72) So 80000/796.72=100.41 Amps. So 460.8 said thing's I don't understand.
I don't get this at all. Your turn.

 

[Hv&Lv]

I took 80000/(460x1.732 =796.72) So 80000/796.72=100.41 Amps. So 460.8 said thing's I don't understand.
I don't get this at all. Your turn.

Multiply that by 1.35...

 

[jumper]

I do either POCO calcs. or residential only.
The POCO calcs are a little different that NEC calcs. With that said, I want to see if I can get this right. Jumper, 135.7? Which comes out to 1/0. (75?) Yes or try again...

480 not 460, but you answer is essentially correct. 1/0 it is.:thumbsup:

 

[jumper]

I took 80000/(460x1.732 =796.72) So 80000/796.72=100.41 Amps. So 460.8 said thing's I don't understand.
I don't get this at all. Your turn.

Use 480V not 460.

460.8 says that the capacitor supply wires must be 135% of capacitor load rating, so multiply your number by 1.35 and then pick a conductor from 310.16.

 

[Flight987]

What are

What are

What are POCO calcs.? Help me on this.

 

[jumper]

What are POCO calcs.? Help me on this.

Forget POCO calcs, you almost have answer. use 480 and not 460 above. multiply by 1.35 and then go to 310.16.

 

[Little Bill]

What is the minimum size THW,or THHN conductor that can be used to wire an 80 kvr,3/0 460 volt Cap.
Help me on this one . Mike doesn't have anything in the work book.

Use 480V not 460.

.

OP said 460V. IMO, you can use that kind of like you are allowed in TBL 430.250. But it comes out the same either way.:thumbsup:

 

[jumper]

OP said 460V. IMO, you can use that kind of like you are allowed in TBL 430.250. But it comes out the same either way.:thumbsup:

Maybe, I was taught to always use the listed nominal voltages for calcs. IDK.

 

[Little Bill]

Maybe, I was taught to always use the listed nominal voltages for calcs. IDK.

It's not written/stated under the capacitor section but it seems similar since caps are often used in a motor circuit. The motor FLC tables state that you can/are permitted to use system voltage ranges of 110-120, 220-240, 440-480V, etc.
If the OP used either 460v or 480V it still works out. If he can grab hold of the basic formula that is.

Edit:I was wrong, if you use 480V instead of 460V you get 129.91 and you could use #1 for that. But since he said answer key said 1/0, they must have meant to use the actual 460V in the question. That would give you the 1/0 answer. (135.55A)