(2) 20/1 breakers fed from same 120V circuit

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anbm

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See attached picture, it appears there are bunch of (2) 20/1 breakers are fed from same 120V circuit (for example: pole #2, #4, #6, etc.).
How does this work in wiring configuration to each breaker? What's kind of application is this? Code compliance?
 

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roger

roger

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anbm said:
Do two breakers share same neutral?
Click to expand...
If they do there is a problem, they would be MWBC's and would need to be on separate legs. Each circuit would need to have it's own neutral. You could still use those breakers for MWBC's but you would have to be sure the MWBC's were on different legs and use handle ties for the two handles associated with them.
 
A

anbm

Senior Member
roger said:
If they do there is a problem, they would be MWBC's and would need to be on separate legs. Each circuit would need to have it's own neutral. You could still use those breakers for MWBC's but you would have to be sure the MWBC's were on different legs and use handle ties for the two handles associated with them.
Click to expand...
Best to load each breaker max. 8 amp.?
 
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jap

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roger said:
If they do there is a problem, they would be MWBC's and would need to be on separate legs. Each circuit would need to have it's own neutral. You could still use those breakers for MWBC's but you would have to be sure the MWBC's were on different legs and use handle ties for the two handles associated with them.
Click to expand...


Much like the breaker they're using on circuits 11 and 13 if those 2 circuits should happens to incorporate a neutral. :)

Jap>
 
LarryFine

LarryFine

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anbm said:
Do two breakers share same neutral?
Click to expand...
Two tandem breakers can be wired to share two neutrals, but only one tandem breaker can not share one.

To expand, that's something you must avoid doing. Here are a couple done correctly. Note that the blacks and the reds are not landed on the same breaker body. They must be wired as a 120/240v circuit.

This way, each neutral only sees difference current as it would in any standard multi-wire branch circuit.

1676354237708.png



Here are tandems that are done incorrectly. Note that there is a black and a red on each breaker body. That's the same as feeding a neutral-sharing pair of circuits from two breakers on the same phase.

Each tandem breaker could supply two 15 (or 20) amp loads and subject the shared neutral to 30 (or 40) amps if wired this way.

1676354303522.png


Note here the panel cover diagram. It literally shows what happens inside a tandem breaker; two independent breakers that share only the power pick-up point and the plastic case.

1676354882333.png


Here is a triplex tandem that allows adding a 2p circuit to a pair of 1p circuits, or adding a pair of 1p circuits to a 2p circuit.

Note that the 2p breaker must be in the middle to receive power from both buses. If it was at either end, it would only be able to supply 2x 120v, and not 240v.

1676355146988.png
 
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jap

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LarryFine said:
Here is a triplex tandem that allows adding a 2p circuit to a pair of 1p circuits, or adding a pair of 1p circuits to a 2p circuit.

Note that the 2p breaker must be in the middle to receive power from both buses. If it was at either end, it would only be able to supply 2x 120v, and not 240v.

View attachment 2564042
Click to expand...

Or, If the handle tie was configured differently, you could also receive 240v power from the 2 "outside" 15 amp breakers in the picture.

It's not a "must" that the 2p configuration be located in the middle of a tandem breaker to receive power from both busses.


JAP?
 
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