ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Tingle off the water spigot
by dsk. 10/15/18 02:36 PM
Board tester power supply?
by JoeTestingEngr. 10/13/18 12:14 AM
Voltage sag
by Trumpy. 10/12/18 06:59 PM
220/230/240V 60Hz Systems
by Trumpy. 10/12/18 06:50 PM
Linear Power Supply Quits Under Load
by JoeTestingEngr. 10/10/18 08:47 PM
New in the Gallery:
What is this for?
Plug terminals
Who's Online Now
1 registered members (HotLine1), 29 guests, and 24 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Polarity at Residential Service #61750
02/02/06 07:38 AM
02/02/06 07:38 AM
Redsy  Offline OP
Joined: Mar 2001
Posts: 2,056
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.

Work Gear for Electricians and the Trades
Re: Polarity at Residential Service #61751
02/02/06 07:54 AM
02/02/06 07:54 AM
pauluk  Offline
Joined: Aug 2001
Posts: 7,520
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).]

Re: Polarity at Residential Service #61752
02/02/06 10:17 AM
02/02/06 10:17 AM
winnie  Offline
Joined: Sep 2003
Posts: 649
boston, ma
It's okay to swap the supply legs if the receptacles are ground up. [Linked Image]


Re: Polarity at Residential Service #61753
02/02/06 11:19 AM
02/02/06 11:19 AM
pauluk  Offline
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Don't you mean if they're ground down?

{Runs for cover.....} [Linked Image]

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:

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? [Linked Image]

Re: Polarity at Residential Service #61754
02/02/06 03:55 PM
02/02/06 03:55 PM
mshaw  Offline
Joined: Jan 2006
Posts: 44
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.

Re: Polarity at Residential Service #61755
02/02/06 09:03 PM
02/02/06 09:03 PM
e57  Offline
Joined: May 2003
Posts: 2,876
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.

Mark Heller
"Well - I oughta....." -Jackie Gleason


2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
kamloops BC Canada
Posts: 1,149
Joined: May 2003
Show All Member Profiles 
Top Posters(30 Days)
sparky 11
Popular Topics(Views)
250,267 Are you busy
187,916 Re: Forum
177,448 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.073s Queries: 14 (0.011s) Memory: 0.9779 MB (Peak: 1.1202 MB) Zlib enabled. Server Time: 2018-10-15 23:34:01 UTC