Can I run 2 panels off the same main breaker? Or?

JohnDS

Senior Member
Location
Suffolk, Long Island
Occupation
Electrician
I have a 200 amp service. The main panel is on the complete opposite side of the basement then where the meter is and there is also a main disconnect outside as well. Recently I had installed an additional 200 amp panel for an apartment. Yes 100 amp or 125 amp would have been fine, but the cost wasn't much more. The kicker is, the apartment panel is right near the meter wall.

Initially I was going to redo the whole service into a 400 amp with two 200 amp meters that would feed each panel. Unfortunately, the multiposition meter I need is not easy to obtain nowadays, so I plan to just temporarily power the apartment panel from my main panel.

Now if you can picture this, the main feed for my main panel comes through the exterior wall from the meter and passes right above the apartment panel and all the way across the basement. It just seems redundant to have to buy a new piece of SER and now go from the main panel all the way back the other way to feed this apartment panel.

So my question: Can't I just tap off the outside 200 amp disconnect with an additional 7ft piece of SEU, run it to the apartment panel and be done with it? I mean I know 2 sets of 2/O copper will not fit inside the 200 amp breaker load terminals, but don't they have some sort of 3way lugs to accomplish this? Or can't I just tap off the SER right above and run a few feet of SER right down to the apartment panel? Really I'd rather tap off the outside disconnect because once I close up the walls in the apartment, the feed is already poked outside for when I get to upgrading to 400 amps.

I know this is a ridiculous idea, but it would really hold me over until I get the service situated. I don't see how this is any more unsafe than the way it is now because everything will still be fused at 200 amps with the appropriate sized feeders.

Thank you for your time.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Seems to me that all you're doing is creating an additional set of service conductors. Not much different than if you had a 400 amp meter and two 200 amp panels downstream.
 

Buck Parrish

Senior Member
Location
NC & IN
I think what you have described is what some services with a trough do. So I agree with Pete, seems okay. As long as the load calulations are up to par.
 

JohnDS

Senior Member
Location
Suffolk, Long Island
Occupation
Electrician
Seems to me that all you're doing is creating an additional set of service conductors. Not much different than if you had a 400 amp meter and two 200 amp panels downstream.
I think what you have described is what some services with a trough do. So I agree with Pete, seems okay. As long as the load calulations are up to par.

So with disturbing this service as little as possible, what would be the best course of action for now? Should I tap SEU right out the bottom of the meter from the same load lugs as the main panel and directly feed the apartment panel(has its own main breaker)? Or should I just come out of the load side of this disconnect somehow?

*By the way, that's just a coaxial pull box there and has nothing to do with the service.
 

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roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
You won't be able to use 2/0 you will need to use a 200 amp conductor
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Why? It sounds like there will be (2) dwelling units, each one served by a 200A feeder. So each of those feeders would get to use the 83% rule.

Cheers, Wayne
Maybe but doubtful. Just for fun tell me how the bill will be divided if there are in fact separate dwellings. I guess it's possible that one occupant will be happy to pay for the others usage.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Maybe but doubtful. Just for fun tell me how the bill will be divided if there are in fact separate dwellings. I guess it's possible that one occupant will be happy to pay for the others usage.
As you said, it may not need to be, e.g. the apartment could be an in-law unit.

Anyway, if there are two separate dwelling units on one service, then at the point their supplies diverge, the feeders for each individual dwelling unit can each use the 83% rule.

Cheers, Wayne
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
As you said, it may not need to be, e.g. the apartment could be an in-law unit.
Which is not a separate dwelling, it is a basically separate room maybe with a separate entrance but not a separate dwelling, even if it has a kitchen.
 

JohnDS

Senior Member
Location
Suffolk, Long Island
Occupation
Electrician
You won't be able to use 2/0 you will need to use a 200 amp conductor
Am I missing something? Is 2/O copper not a 200 amp conductor? That's all that is used for 200 amp services around here.

Maybe but doubtful. Just for fun tell me how the bill will be divided if there are in fact separate dwellings. I guess it's possible that one occupant will be happy to pay for the others usage.

This is a temporary setup, it's not intended to have the tenant pay for their own electric until the multi position meter is available and installed. For now, electric is included in the rent if it's being done this way.

So with disturbing this service as little as possible, what would be the best course of action for now? Should I tap SEU right out the bottom of the meter from the same load lugs as the main panel and directly feed the apartment panel(has its own main breaker)? Or should I just come out of the load side of this disconnect somehow?
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
You can not use the reduction unless the feeder serves the whole load of the dwelling as in singular.
 

Buck Parrish

Senior Member
Location
NC & IN
So with disturbing this service as little as possible, what would be the best course of action for now? Should I tap SEU right out the bottom of the meter from the same load lugs as the main panel and directly feed the apartment panel(has its own main breaker)? Or should I just come out of the load side of this disconnect somehow?

*By the way, that's just a coaxial pull box there and has nothing to do with the service.
Remove the disconnect or take the guts out and use it as a j-box for both the apartment and the house.. Make that a "gutter' or j-box set two disconnects beside it. (y)
Don't mess with the meter, unless your in Indiana. Its common to see three or four conduits coming out of a meter base in rual Indiana, no disconnects any where in sight.:oops:
 
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wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Which is not a separate dwelling, it is a basically separate room maybe with a separate entrance but not a separate dwelling, even if it has a kitchen.
I'd say an attached unit with a separate outdoor entrance, and with "permanent provisions for living, sleeping, cooking, and sanitation" is a separate dwelling. And I'd call that an in-law unit or ADU, assuming it's smaller than the main unit.

Cheers, Wayne
 

kwired

Electron manager
Location
NE Nebraska
Maybe but doubtful. Just for fun tell me how the bill will be divided if there are in fact separate dwellings. I guess it's possible that one occupant will be happy to pay for the others usage.
Billing doesn't matter to NEC that is a POCO issue, the fact it is supplying two separate dwelling units is all that matters in being able to use the 83% rule.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
I'd say an attached unit with a separate outdoor entrance, and with "permanent provisions for living, sleeping, cooking, and sanitation" is a separate dwelling. And I'd call that an in-law unit or ADU.

Cheers, Wayne
And unless you can show me you are the governing agency that makes this decision I would tell you to go pound sand.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
And unless you can show me you are the governing agency that makes this decision I would tell you to go pound sand.
Here's the definition from the NEC which controls the use of (2020) 310.12:

"Dwelling Unit. A single unit, providing complete and independent living facilities for one or more persons, including permanent provisions for living, sleeping, cooking, and sanitation."

Would you explain how it's possible to interpret an ADU as other than a second dwelling unit? I'm not seeing it.

Cheers, Wayne
 

kwired

Electron manager
Location
NE Nebraska
Which is not a separate dwelling, it is a basically separate room maybe with a separate entrance but not a separate dwelling, even if it has a kitchen.
Unless you know something OP hadn't posted, we are assuming it does meet art 100 definition of a dwelling, on it's own. If it would have to share say a kitchen or a bathroom with the main unit, then it doesn't fit the definition.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Billing doesn't matter to NEC that is a POCO issue, the fact it is supplying two separate dwelling units is all that matters in being able to use the 83% rule.
You missed the point, how many "main feeders" can you have from one service?
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
You missed the point, how many "main feeders" can you have from one service?
What do you mean by service? If you mean "a set of conductors that lands on a service disconnect" then the arrangement in the OP will be two services, each supply one dwelling unit. If you mean "service conductors, underground" or "service conductors, overhead" then the arrangement in the OP would be two main feeders for two different dwelling units on one service.

Cheers, Wayne
 
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