Amperage rating on circuit

HereForBeer

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May 2017
Location
Canton, Ohio
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I have to add (3) 10 breakers to an existing control panel. There is enough capacity in regards to the main MCCB. I don't have any room on the distribution block..

Can I jumper off the line side of other CB's? The row I will be adding the 3 additional breakers already has multiple CB's the same size.. I'm just unsure of the amperage capacity on the wire once I start jumpering.

There are (3) 14 AWG feeding the CB's from the distribution block, If I jumper from that CB to another then another then another... wouldn't that overload the wire amperage capacity since it would be carrying current from 4 different loads after the CB?

Do I need to size the wire for the FL of all loads when using jumpers in this manner?
 
My understanding is that this is not OK to do, unless the conductors feeding the original downstream CB and all jumpers to the next CBs are sized for the main CB, which is unlikely. That's because the panel probably takes advantage of the tap rule, which can allow you to size conductors based on the size of a downstream CB, provided that they terminate directly at the CB and don't branch anywhere else.
 
My understanding is that this is not OK to do, unless the conductors feeding the original downstream CB and all jumpers to the next CBs are sized for the main CB, which is unlikely. That's because the panel probably takes advantage of the tap rule, which can allow you to size conductors based on the size of a downstream CB, provided that they terminate directly at the CB and don't branch anywhere else.

Are you saying I would have to run wire rated for the 200A MCCB if I wanted to branch a few CB's downstream?

I can't use wire rated for the total amperage of the jumpered CBs on that circuit?
 
Yes, I believe that anything else would not be up to code. Look up "tap tule explained".

Not saying I haven't seen it done, of course. Would love to have someone chime in and tell us there is an exception buried somewhere in the book.

Are you able to fit in another small distribution block somewhere to branch out to the new CBs?
 
Last edited:
Many breakers have a jumper bar accessory that can be used just for this purpose. Check w/the manufacturer or distributor.

Thumbs up to you for knowing to ask this question but it is scary how many people are designing and modifying electrical panels that are not qualified.
 
I believe I figured it out.

From my understanding, a lot of the tap rule doesn’t apply to a control panel.

If I have (4) 20 amp breakers and I want to use jumpers on the line side.. the first tap has to be rated for all (4) CBs, the 1st jumper is rated at the 3 remaining CBs, the 2nd jumper is rated for the remaining 2 CBs, and the final jumper is rated for the last CB.

But just to be safe, I used conductors rated for all 4 CBs as my jumpers vs stepping down each jumper.
 
We don't know what brand of breaker you have, but 90% of small breakers like that do NOT have lugs rated for more than one conductor. If it does, there must be a label ON THE BREAKER stating that.
 
We don't know what brand of breaker you have, but 90% of small breakers like that do NOT have lugs rated for more than one conductor. If it does, there must be a label ON THE BREAKER stating that.

Code-wise, I completely agree. Practically however, a two-wire ferrule solves that problem (assuming a cage clamp design). Sometimes, you have to make it work when retrofitting machinery.


-rpoet
 

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