multiwire branch circuits

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jap2525

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Am I understanding this correctly?
On a 240v single phase service in a house if 2 ungrounded conductors share a neutral and terminate on the same yoke of a receptacle approved handle tyes are required to disconnect both circuits 210.4b.but if the 2 ungrounded conductors feed loads that arent on the same yoke approved handle tyes are not required but the neutral must be made up to where disconnection of a device does not interupt the neutral path 300.13b.My question is if approved handle tyes are not used in the second instance you could shut 1 circuit off in the panel and disconnect the neutral from the neutral bar and have a load on it from the other circuit that is still energized if something is being used.(equally as dangerous)Am I missing something here?
 
Re: multiwire branch circuits

The second circuit would have An ungrounded and potentially energized conductor connected but there would be no hazard I can see. Threre's just no neutral so circuit.

Editted in: There would be a definate hazard if you removed only the ungrounded conductor from a multiwire circuit.

[ October 13, 2004, 01:14 PM: Message edited by: physis ]
 
Re: multiwire branch circuits

if you had a 500watt quarts light on circuit A and the same on circuit B.If you shut off circuit A at the panel and disconnected the neutral,you would get an arc at disconnection and if you were to get between the neutral conductor and any grounded surface you would catch the load of the 500w quarts on cir.B.

[ October 13, 2004, 01:18 PM: Message edited by: jap2525 ]
 
Re: multiwire branch circuits

I see in a lot of old buildings with K&T the lighting switches are switching the neutral instead of the hot. It annoys me but it's no more dangerous than what I think you're describing.
 
Re: multiwire branch circuits

The same would be true of any load with inductance. Under any cicumstances. The multiwire cicuit makes no difference there.

Editted in: Let me put it this way. If you cut the beaker on cicuit A then circuit B's hot and the neutral are just the same as any other single pole circuit.

[ October 13, 2004, 01:28 PM: Message edited by: physis ]
 
Re: multiwire branch circuits

I'm not talking about switching the neutral.That is not the same circumstance.
 
Re: multiwire branch circuits

simultaneous opening of a multiwire circuit on the same yoke keeps someone from getting shocked.On a multiwire circuit that is not on the same yoke there is still the shock potential if the neutral is disconnected at the panel and you get in the return path.Without some investigating you dont know if a neutral is part of a multiwire circuit or not until you disconnect it.Then there is the possibility of finding out the hard way.
 
Re: multiwire branch circuits

It still is the same. You disconnting the neutral by hand only allows you to see the arc that would otherwise be contained in the switch. Although it may be suppressed inside the switch by grease, you too could put a blob of grease on the neutral connection before you disconnect it.
 
Re: multiwire branch circuits

I can see why they require it on the same yoke,I'm just surprised it is not required on any multiwire branch circuit with a shared neutral.
 
Re: multiwire branch circuits

We were never talking about disconnecting only the neutral from a multiwire circuit.
 
Re: multiwire branch circuits

switching the neutral instead of the hot although a code violation is not the same as a multiwire branch circuit unless you have 2 hot conductors involved with the 1 neutral you are switching.If there was only 1 ungrounded conductor with your switched neutral it is not a multiwire circuit.
 
Re: multiwire branch circuits

It's because on a two pole circuit that kicks the breaker you want both hots removed.

On a Multiwire circuit you can interupt one pole and the other side can still operate normally.
 
Re: multiwire branch circuits

And you type faster than me. This whole thead is out of sequence because I can't keep up.
 
Re: multiwire branch circuits

No I'm not talking about disconnecting only the neutral.I'm saying if you shut off circuit A and circuit b is left on,,,,,, the shock potential still exists if the neutral is disconnected in the panel from the load on circuit B.The handles are not tyed together,yet the neutral is shared and has return current on it.
 
Re: multiwire branch circuits

There is no reason to remove both hots if the breaker trips for one of the circuits.That is not the reason for handle tyes on the same yoke.
 
Re: multiwire branch circuits

I'm just trying to figure out why they require handle tyes on a multiwire circuit on the same yoke where someone could get shocked by unhooking the hots at the load end and not requiring handle tyes on a multiwire circuit, not on the same yoke, where someone could get shocked by unhooking the neutral at the line end.
 
Re: multiwire branch circuits

Jap, the truth is that only "qualified individuals" should be in the panel and they would be able to recognize this as a "Multi Wire Circuit".

Roger
 
Re: multiwire branch circuits

I agree with you roger,but then again only qualified people should be doing electrical work and should be able to recognize 2 circuits on a split receptacle.
 
Re: multiwire branch circuits

In a perfect world yes this argument would hold water.But this is not a perfect world and unqualified personell do work all the time.To me the reason for yhis requirement is to prevent accidential shock to even a quote quallified person.
 
Re: multiwire branch circuits

Can we or should we be worrying about unqualified people doing electrical work.They should have enough since to know they can get electrocuted.If they proceed with doing what there not skilled at then that's there fault.Would they run across 6 lanes of interstate and if they get hit say we should have protected them ?
 
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