Small breaker powers larger breaker

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anbm

Senior Member
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Designer
Will there be any code issues to use 700A breaker to feed the existing elec. panel with 1200A main CB?
Panel draws around 456A max.
 
Also the wiring from 700A to 1200A breaker is (2) sets of 600KCM which is good for 800A, will this violate NEC 240 as wiring rating is less than downstream breaker rating (1200A)?
 
anbm said:
Will there be any code issues to use 700A breaker to feed the existing elec. panel with 1200A main CB?
Panel draws around 456A max.
Click to expand...
None that I can think of if you are telling us the whole story. I have learned over the years that there are many times when parts of the story don't get told that turn out to be relevant. Like why someone would have a 1200 amp main breaker on an existing panel that only has 456 amps of demand.
 
petersonra said:
None that I can think of if you are telling us the whole story. I have learned over the years that there are many times when parts of the story don't get told that turn out to be relevant. Like why someone would have a 1200 amp main breaker on an existing panel that only has 456 amps of demand.
Click to expand...

Sorry, 456A is metering data, calculated numbers of panel load is probably close to 1000A +/-. Just try to re-feed that existing 1200A panel from different source. 😃
 
anbm said:
Will there be any code issues to use 700A breaker to feed the existing elec. panel with 1200A main CB?
Panel draws around 456A max.
Click to expand...
The 1200a breaker would basically function as a disconnect. No issues.
 
Ok I'll give in and try to come up with some potential issues:

1. If the 1200 A equipment was service equipment, you will need to separate the Ns and Gs if you add a new service disconnect ahead of it.

2. Make sure you still have any necessary series ratings.

3. If coordination happens to be a concern, check that.

4. No metering issues? For example if the 1200 had a utility metering section.

That's all I got. ...
 
electrofelon said:
Ok I'll give in and try to come up with some potential issues:

1. If the 1200 A equipment was service equipment, you will need to separate the Ns and Gs if you add a new service disconnect ahead of it.

2. Make sure you still have any necessary series ratings.

3. If coordination happens to be a concern, check that.

4. No metering issues? For example if the 1200 had a utility metering section.

That's all I got. ...
Click to expand...
2. Why series rating is needed in this case?
1. Good input.
3, 4 do not apply.
 
anbm said:
2. Why series rating is needed in this case?
1. Good input.
3, 4 do not apply.
Click to expand...
Well if something downstream has a series rating with the 1200, as long as your 700 is fully rated you should be fine. You can add a fully rated breaker ahead of a tested combination. If the AIC is not compliant with the AFC, and you have to bring it up to snuff with the new work, you may have to investigate the series ratings and print remove the 1200 to get it to work.
 
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