# Mixed use calculation- Help!



## Elec tricka (Jun 12, 2015)

I typically do residential 100-200amp single family services and got this thrown at me.

200a restaurant "greasy spoon".
60a " by calculation" apartment A 
60a " by calculation" apartment B

now being fed by a 400 amp service to a trough split to 3 meter cans down to a 200a and 2 -100a disconnects and it's crumbling.

The apartments are going under 1 meter to a 200a disconnect then split to their respective 100a breakers. The restaurant will have its own meter to a 200a disconnect. 

How do I calculate the size service entrance wire down the mast to the trough??


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## Elec tricka (Jun 12, 2015)

Hello.... is there anybody in there is there anyone at home?


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## Elec tricka (Jun 12, 2015)

Hello.... is there anybody in there just nod if you can hear me BUM BUM BUM is there anyone at home?


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## MikeFL (Apr 16, 2016)

Elec tricka said:


> I typically do residential 100-200amp single family services and got this thrown at me.
> 
> 200a restaurant "greasy spoon".
> 60a " by calculation" apartment A
> ...


What are you doing? A service change? Repair work?

If it's a 400A service I'd guess AHJ is going to want to see you size the SEC's for 400A. Although you're not pulling 400A, it's still a 400A service.

Ignore my question. I found the "crumbling part." It was a bit confusing.

You're coming in to 2 meters then to 2x200A discos and from there one 200A goes to greasy spoon and the other 200A goes to 2x100A apartments. I still say stick with 400A.

Did I understand you right?


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## Elec tricka (Jun 12, 2015)

Yes you got it.

like i said i'm a resi. guy 200a 4/0 aluminum.
Commercial doesn't use the down graded cheat sheet, just wondered if there was a mix number math some were.
For a 28 foot mast on a two meter two disconnect it's probably not worth the brain work.
so that puts me at 700 kcmil aluminum and a 3 inch mast.
thanks for the in put, it's hard to be a one man thinking crew.


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## MikeFL (Apr 16, 2016)

Elec tricka said:


> ... hard to be a one man thinking crew.


When I worked in the bldg dept and wanted a legal opinion I'd write it all out with the background, cite applicable statute, present the situation at hand, and format my question. 90% of the time I'd answer it myself by laying everything out logically and never needed to send it on to the city attorney. Same happens on here. Lay it out, type it up, and sometimes the answer just comes to you. Hit delete and carry on.

Let's see if others have any input on the matter at hand...


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## ROCKDOG (Sep 14, 2011)

I would use parallel 2" conduit, each with 3/0 Cu. I don't like huge conduit. But, it's only going straight up, then its not so bad.


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## MechanicalDVR (Dec 29, 2007)

ROCKDOG said:


> I would use parallel 2" conduit, each with 3/0 Cu. I don't like huge conduit. But, it's only going straight up, then its not so bad.


And the price of the copper will put you right out of the ballpark.


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## billo (Feb 1, 2017)

Elec tricka said:


> I typically do residential 100-200amp single family services and got this thrown at me.
> 
> 200a restaurant "greasy spoon".
> 60a " by calculation" apartment A
> ...


If it's a 400A service, then you should use 400A wire. Which is 3#500kcmil's if it's single-phase, 4#500kcmil's if it's 3-phase, 4-wire.

I'm not sure about the residential load, but normally, you can take the peak demand for the last 12 months (which is in KW), divide that by 0.8pf, multiply that by 1.25% and use that as your connected load.

The residential load you might have to do the typical residential load calculations.


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