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#98935 - 06/27/06 08:15 AM Suplying a load from two different circuits
tdhorne Offline
Member

Registered: 03/22/01
Posts: 344
Loc: Maryland, USA
I'm hoping that those of you with a better memory might be able to point me to the code section that forbids supplying a load from two different circuits. I tried a search but I didn't use the right search terms to get what I needed. I am aware of 300.3 (B) but I was hoping for something more on point. The load in question takes its ungrounded conductor from a 240 volt circuit and its grounded conductor from a 120 volt circuit. Thanks in advance for any help.
--
Tom Horne
_________________________
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison

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#98936 - 06/27/06 09:00 AM Re: Suplying a load from two different circuits
hbiss Offline
Member

Registered: 12/16/03
Posts: 893
Loc: Hawthorne, NY USA
Don't think you're going to find one. I've seen equipment that use 208/3 phase and a separate 120 volt circuit for the controls.

-Hal
_________________________
www.myphonetechs.com

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#98937 - 06/27/06 09:35 AM Re: Suplying a load from two different circuits
Creighton Offline
Member

Registered: 01/06/02
Posts: 56
Loc: Hayward, CA
What you describe is not permitted. See 210.4(A). "All conductors shall originate from the same panelbord." Although this applies to multiwire circuits I believe it to be a good rule to follow in any case.
Creighton

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#98938 - 06/27/06 10:16 AM Re: Suplying a load from two different circuits
Jonno Offline
Member

Registered: 05/27/06
Posts: 20
I would go so far as to say that it is fine and sometimes needed to suply equipment from multiple sources, 600v motors with 120v control as an example, or anything with mixed AC/DC.

This strikes me as more of an issue of conductor bundeling.

It is necissary to keep all of the conductors (grounded and non) in a circuit bundled to ensure a ballanced current flow, which reduces the inducatnce of the wire run, prevents stray EMF, and prevent conduit heating. That bundle should be continuous to the panel (hense originatng for the same pannel) wher it is consoldated and then continues bundled to the POCO.

I don't know the code section off hand, and bing a Canadian I'm not sure it would help. I know this has ben dicused in other threads.

To sum up all conductors on the same circuit (ie feeding the same load) must run in the same conduit (be it cabtire, romex, EMT etc.)

Hope this helps,
Jon

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#98939 - 06/27/06 10:32 AM Re: Suplying a load from two different circuits
Jonno Offline
Member

Registered: 05/27/06
Posts: 20
This may help, it is a thread on bundeling conductors: http://electrical-contractor.net/ubb/Forum4/HTML/000975.html

With two ciurcuts using the same grounded conductor, I am also concerned about overcurrent protection, which is normaly provided by the non-gronded conductor's protection

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#98940 - 06/27/06 06:02 PM Re: Suplying a load from two different circuits
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
Tom:
Are you saying that one leg of a 240 volt circuit is 'tapped' and using the neutral of another circuit??

With all due respect to Creighton, you didn't state coming from multiple panels (sources) distinctly.

Is this a control circuit (120 volt) for a motor/machine??

Good practice would be 2 hots for 240 v; 1 hot-1 neut for 120 plus grounds as required.

As to an NEC Article?? I'll have to look tommorow; or bring this up at the Assoc. meeting Wed Nite.

John

PS: Almost forgot...I have labels stating "More then one source of power within this enclosure/equipment/cabinet"


[This message has been edited by HotLine1 (edited 06-27-2006).]
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#98941 - 06/29/06 08:52 PM Re: Suplying a load from two different circuits
e57 Offline
Member

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
An example of where it is allowed to have 2 or more can be found in 430.113. 620.52. Otherwise it can depend on the type of equipment.... Whats the example?

Either way I think its a bad idea to have a neutral from a different circuit used, as it may over-load the neutral....
_________________________
Mark Heller
"Well - I oughta....." -Jackie Gleason

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#98942 - 07/01/06 04:59 AM Re: Suplying a load from two different circuits
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
Look at 300.3(B). This section requires that all conductors of a circuit be contained in the same cable or raceway.
Using the 'hot' from a 240 volt branch circuit used for other purposes and returning on the neutral from another is bad for two reasons. One is the stray EMF you build by having the circuit conductors separated; two is the possibility of shock to some poor electrician who is trying to work on the circuit having the "pirated" neutral connection. He turns the CB "off", then checks for voltage at the receptacle box. Finding none, he proceeds to tear into the wiring, only to get caught up on the open neutral, which is carrying the return current from our "pirated" connection. Ouch!
I once got caught on the return from a 277 volt lighting circuit. Hurts for days.
_________________________
Earl

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#98943 - 07/01/06 05:10 AM Re: Suplying a load from two different circuits
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
 Quote:
Look at 300.3(B). This section requires that all conductors of a circuit be contained in the same cable or raceway.


Not always.

Look at 300.3(B)(3).

Bob
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#98944 - 07/01/06 05:22 PM Re: Suplying a load from two different circuits
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
Good point!

By using the neutral from one branch circuit, with the hot from another branch circuit, you have made a multiwire branch circuit.
Section 210.4(C) requires a multiwire branch circuit to feed only line to neutral loads, unless you use a CB that open all hots.
You have a 240 volt CB with a 240 volt load and you have another 120 volt load as parts of this multiwire branch circuit. Nor are these CBs tied together.

[This message has been edited by earlydean (edited 07-01-2006).]
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Earl

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