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#61750 - 02/02/06 03:38 AM Polarity at Residential Service
Redsy Offline
Member
Registered: 03/28/01
Posts: 2056
Loc: Bucks County PA
A 320-amp residential meter feeds 2 150-amp service panels with 2 piecse of 2/0 SEU.
At the meter, each SEU is connected as Black=L1 and Red=L2. At the main CBs, each are connected as Red=L1 and Black=L2.
Although this seems OK, it just doesn't sit well with me.
On the other hand, it doesnt seem any different than randomly connecting a 240-volt load with no consideration to polarity.
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#61751 - 02/02/06 03:54 AM Re: Polarity at Residential Service
pauluk Offline
Member
Registered: 08/11/01
Posts: 7520
Loc: Norfolk, England
I can't see it being a problem. At least there's still consistency between the two panels, i.e. L1 in one panel is on the same leg of the supply as L1 in the other panel.


[This message has been edited by pauluk (edited 02-02-2006).]
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#61752 - 02/02/06 06:17 AM Re: Polarity at Residential Service
winnie Offline
Member
Registered: 09/15/03
Posts: 649
Loc: boston, ma
It's okay to swap the supply legs if the receptacles are ground up.

-Jon
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#61753 - 02/02/06 07:19 AM Re: Polarity at Residential Service
pauluk Offline
Member
Registered: 08/11/01
Posts: 7520
Loc: Norfolk, England
Don't you mean if they're ground down?

{Runs for cover.....}

Quote:
it doesnt seem any different than randomly connecting a 240-volt load with no consideration to polarity.


Not that this would affect your specific case, but thinking about it some more, it seems that in the past such a random connection would not have been to code. From the 1971 NEC:

Quote:
210-5(c) Ungrounded conductor. {.....} All ungrounded conductors of the same color shall be connected to the same ungrounded feeder conductor and the conductors for systems of different voltages shall be different colors.


So presumably at that time, if you had black and red on the incoming feeder to the panel, you would then be required to match up your blacks and reds correspondingly on 240V branch circuits.

There seems to be no equivalent stipulation in the '02 NEC. In fact I can't even see anything which suggests matching colors on 3-phase anymore. Does that mean that however confusing it might be, it would now be to code to use black/red/blue for A/B/C at one point and then switch to blue/black/red or some other order elsewhere?
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#61754 - 02/02/06 11:55 AM Re: Polarity at Residential Service
mshaw Offline
Member
Registered: 01/11/06
Posts: 44
Loc: Fairborn, Oh, USA
I would say it makes no real differece. I would keep L1 to L1 and L2 to L2 just for workmanship. Because the two are not what I would consider truely phased in the commercial sence they are 180 degrees out of phase with each other. The phasing is generated by the transformer not the utility. So in reality switching them would pose no issue in residential applications.
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#61755 - 02/02/06 05:03 PM Re: Polarity at Residential Service
e57 Offline
Member
Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
I would change them to be all the same straight through. Down the line, if someone has to troubleshoot they could be cursing your name.
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