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New sub-panel in house addition, do I have this right?

sjoseph316

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Nov 20, 2023
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20
Hey all!
I want to put a sub panel in the basement of our addition. The main breaker box is 65 feet from the location I want the sub panel. I need 220 in the sub panel because I will be transferring the stove and dryer to it from the main.
I have 200 amp service and the sub panel I bought is a 125 amp. The addition is a big living room, kitchen, garage and rec room. The old kitchen will become a mud room and the old living room will become a spare bedroom. So the only things I will be adding to the entire load are some outlets and lights, and I will be eliminating some outlets from the old kitchen and living room.
Does this look correct for what I’m trying to do?

125 amp sub panel 65 feet from main, from the basement of the house to the garage of the new, they are side by side no wire will be outside
100 amp breaker in main panel to run sub panel
2/0-2/0-2/0-1 ALUMINUM SER CABLE

Also, If the 2/0-2/0-2/0-1 ALUMINUM SER CABLE is good to use, does it have to be in conduit if the whole run will be inside?

Thank you for the help, much appreciated!
 

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wyliesdiesels

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2/0 AL is fine but if you do a load calc and the load is 120a or less (most likely is), you could get by with 1/0 AL and a 125a breaker since 1/0 is rated for 120a and 120a is not a standard breaker size

SER doesnt need to be ran in conduit. just make sure its "not subject to damage"
 

kngelv

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Some inspectors will not pass that breaker setup. You might have to have a larger breaker in the main panel.

James
 

mm08822

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Some inspectors will not pass that breaker setup. You might have to have a larger breaker in the main panel.

James
The largest cb the main panel will take is 125a. So therefore, 1/0 is sufficient.

The feeder doesn't even need to be 125a. Do the load calc and it will surely be lower. My bigger concern would be to buy a panel with enough branch circuit capacity.
 

kngelv

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I wish we could get a ******** emoji added to the options:

1000002398.png

For posts like this
All right wiseguys. This literally just happened in my own newly built 2nd garage two months ago. I know there is nothing in the code that says this - I’m a friggin electrician. You ever hear of something called “authority having jurisdiction”? That’s straight out of the NEC codebook. My local inspector did not want a 90A breaker feeding a 100A sub-panel. He’s the local authority so I had to change it.

James
 
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wyliesdiesels

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All right wiseguys. This literally just happened in my own newly built 2nd garage two months ago. I know there is nothing in the code that says this - I’m a friggin electrician. You ever hear of something called “authority having jurisdiction”? That’s straight out of the NEC codebook. My local inspector did not want a 90A breaker feeding a 100A sub-panel. He’s the local authority so I had to change it.

James
not how it works. If there is no code, then what is this authority enforcing? they cant just make up rules/codes as they go and demand you abide by them.

the only time they can make you change something that is not in the NEC is if the AHJ, aka building dept., has local WRITTEN amendments.

absent of that, nope sorry dont have to do what you want.

BTW the inspector is NOT the AHJ. he is a representative of the AHJ and they do make mistakes all the time. many of them dont even know code to save their life.

you sir bent over backwards for their BS claims.

As an electrician you should know all this... sadly many dont...

millions of panels in this country are fed by breakers that are rated for less than the panel rating. there is no issue whatsoever with that. the inspector had no clue what he was talking about....

on the flipside, if the panel was rated for 90a and you fed it with a 100a breaker (and no main disconnect was in the panel), only THEN would there be an issue...

BTW what size wire were you feeding that panel with?
 

kngelv

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#2 THHN copper. The irony is my attached garage has a 60A sub-panel being fed with a 50A breaker. He was a nice enough guy and I did not feel like arguing with him.

James
 

wyliesdiesels

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#2 THHN copper. The irony is my attached garage has a 60A sub-panel being fed with a 50A breaker. He was a nice enough guy and I did not feel like arguing with him.

James
you should have. he is ignorant and wasted your time and money. not ok. send a complaint to his boss

inspectors like that should not be allowed to run amok... they are ignorant and worthless...
 

Norcal

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13,765
All right wiseguys. This literally just happened in my own newly built 2nd garage two months ago. I know there is nothing in the code that says this - I’m a friggin electrician. You ever hear of something called “authority having jurisdiction”? That’s straight out of the NEC codebook. My local inspector did not want a 90A breaker feeding a 100A sub-panel. He’s the local authority so I had to change it.

James
A inspector is not the AHJ, they are a representative of the AHJ.
 

dcg9381

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not how it works. If there is no code, then what is this authority enforcing? they cant just make up rules/codes as they go and demand you abide by them.

the only time they can make you change something that is not in the NEC is if the AHJ, aka building dept., has local WRITTEN amendments.

absent of that, nope sorry dont have to do what you want.

BTW the inspector is NOT the AHJ. he is a representative of the AHJ and they do make mistakes all the time. many of them dont even know code to save their life.
Wylie, I've issues with this too, installing solar systems with "rapid shut down" (NEC code compliant). They still want "physical disconnects" (rapid shut down makes these unnecessary).

But you're right, they did have that written requirement. Solar is like a red headed step child to electricians here..

I pointed out NEC and they said "policy". Put me in the "didn't argue" box too.
 

mm08822

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If "They" was the POCO, then that was their requirement for you to comply with if you wanted to remain connected to their grid.
NEC doesn't apply at this interface.

POCOs had that requirement in place long before rapid shut downs were a thing. POCOs are a more visual crowd wanting to see knife blade disconnects open.

Rapid shutdowns differ in that they should disconnect the DC power at the panels/combiner box to reduce the exposure to that DC line eventually hitting the inverter. As a house is burning, water is sprayed everywhere and contact with that live DC line is very possible. Inverter islanding doesn't eliminate this. Nor would a utility disconnect.

Both of these disconnects serve 2 different purposes while the HO only sees it as a production stopper.
 

mm08822

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Yeah, but I've got to go look for those. The "like" button is fast and easy, but needs additional options
I meant those to be added into that list. Or give the option to configure our own readily available pick list.
 
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