any issues

[petersonra]

1600A Cb.

I need 3 taps off it to feed 3 smaller breakers. Only 5 ports in the lugs.

Any problem with making the tap with a larger conductor (say 500 kcm) and then splicing that to two smaller conductors (say 3/0) that actually land at the smaller breakers?

Now next question. What is the best (least expensive) way to make this splice? My first thought was some crimped on barrel type connectors but that option is not available to me for no good reason, but it is just not available. Not a huge fan of compression lugs that get bolted together but that is an option.

 

[infinity]

You cannot tap a tap so your 500 kcmil to a smaller conductor won't work.

240.21 Location in Circuit. Overcurrent protection shall
be provided in each ungrounded circuit conductor and shall
be located at the point where the conductors receive their
supply except as specified in 240.21(A) through (H). Conduc-
tors supplied under the provisions of 240.21(A) through (H)
shall not supply another conductor except through an overcur-
rent protective device meeting the requirements of 240.4.

 

[augie47]

I agree with Rob,
I think the least expensive way would be to replace the 5 port lugs if possible.
My next thought, although definitely not inexpensive be a large "polaris" connector.

 

[don_resqcapt19]

What are the ratings of the smaller breaker that will be fed? What is the wire length from the 1600 amp breaker to the smaller breakers?

 

[petersonra]

What are the ratings of the smaller breaker that will be fed? What is the wire length from the 1600 amp breaker to the smaller breakers?

I am not tapping a tap.

There would be a tap wire coming off the 1600A CB. It would splice into two parallel smaller conductors of similar combined ampacity that would connect to the smaller CB.

this would be repeated for each of the smaller CBs.

All in the same cabinet.

 

[infinity]

I am not tapping a tap.

There would be a tap wire coming off the 1600A CB. It would splice into two parallel smaller conductors of similar combined ampacity that would connect to the smaller CB.

this would be repeated for each of the smaller CBs.

I see no code provision that would allow this. Your single larger conductor is the tap conductor which cannot splice to any combination of smaller conductors.

 

[don_resqcapt19]

I don't see that installation as "tapping a tap". The parallel conductors have an ampacity (400A) that is greater than that of the single conductor (380A), however neither has enough ampacity for this application.

 

[petersonra]

I see no code provision that would allow this. Your single larger conductor is the tap conductor which cannot splice to any combination of smaller conductors.

take a close look at what 240.21 (B)(1) actually says versus what 240.21 (B)(2) says. I would be under the (B)(1) rule.

 

[david luchini]

take a close look at what 240.21 (B)(1) actually says versus what 240.21 (B)(2) says. I would be under the (B)(1) rule.

Your installation would violate 240.21...specifically "Conductors supplied under the provisions of 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4."

 

[don_resqcapt19]

take a close look at what 240.21 (B)(1) actually says versus what 240.21 (B)(2) says. I would be under the (B)(1) rule.

I don't see anything that is different as far as "tapping a tap" in those two sections.

 

[infinity]

Your installation would violate 240.21...specifically "Conductors supplied under the provisions of 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4."

That was my feeling as well. The larger conductor cannot connect to the two other conductors.

 

[petersonra]

Your installation would violate 240.21...specifically "Conductors supplied under the provisions of 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4."

that is a tough one to get past. I am just trying to get past it though.

 

[david luchini]

that is a tough one to get past. I am just trying to get past it though.

Can't get by with a single 700mcm to each sub breaker?

 

[GoldDigger]

I see no code provision that would allow this. Your single larger conductor is the tap conductor which cannot splice to any combination of smaller conductors.

To avoid tapping a tap, you could put a 900A CB on each of the larger wires somewhere before they split. Either at the main or at the location of the smaller CBs. Not a practical option, but a technically allowable one, I think.

 

[petersonra]

Can't get by with a single 700mcm to each sub breaker?

why would I need a 700kcm?


240.21 allows for taps under limited circumstances in subparagraphs (A) through (H). You have to meet one of them.

240.21 (F) points you to 430.28 for motor feeder taps.

430.28 points us to part II (of article 430) for determining the conductor ampacity required.

430.21 in part II says 125% of FLC. 125% of 302A is 378 amps that is covered by a 500 kcm (380A).

 

[david luchini]

why would I need a 700kcm?


240.21 allows for taps under limited circumstances in subparagraphs (A) through (H). You have to meet one of them.

240.21 (F) points you to 430.28 for motor feeder taps.

430.28 points us to part II (of article 430) for determining the conductor ampacity required.

430.21 in part II says 125% of FLC. 125% of 302A is 378 amps that is covered by a 500 kcm (380A).

Well, you did say you were tapping in accordance with 240.21(B)(1), not 240.21(F).

 

[petersonra]

Well, you did say you were tapping in accordance with 240.21(B)(1), not 240.21(F).

thinking out loud, and not thinking it quite all the way through.

it turns out the 450A breakers have lugs on them that can take a 500 kcm wire if I can make the bends.

 

[don_resqcapt19]

What specific code section specifies the overcurrent protection for parallel conductors? In general the code tends to treat the paralleled conductors as a single conductors and I would not cite the "tapping of a tap" rule for this application.

 

[david luchini]

thinking out loud, and not thinking it quite all the way through.

it turns out the 450A breakers have lugs on them that can take a 500 kcm wire if I can make the bends.

I think you've found a technicality with 240.28(1), but I'm not sure it's what the code intends. It basically wipes out the motor feeder protection requirements of 430.61 for feeders 10' or shorter.

 

[petersonra]

What specific code section specifies the overcurrent protection for parallel conductors? In general the code tends to treat the paralleled conductors as a single conductors and I would not cite the "tapping of a tap" rule for this application.

That was my initial thinking, but there is that pesky language

shall not supply another conductor except through an overcurrent protective device

I was thinking that there was language somewhere that said to treat parallel conductors as a single conductor but it does not actually say that.