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Expecting 120 volts and finding 240 volts #1675 05/20/01 07:52 PM
Joined: May 2001
Posts: 160
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Chris Rudolph Offline OP
Member
I am concerned about opening a switch or receptacle box in a residence and finding a multiwire circuit,2 ungrounded(hot) and a shared neutral with the hot conductors measuring 240 volts between them.I believe this is allowed per the NEC to share the neutral and feed the circuits from both sides of the panel in order to reduce the neutral current thus allowing for only one neutral conductor.
This appears to me to be a saftey issue and maybe there should be a notice posted on the box stating that 240 volts is present.
What is the opinion of the group?

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Re: Expecting 120 volts and finding 240 volts #1676 05/20/01 08:05 PM
Joined: Oct 2000
Posts: 5,389
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sparky Offline
Member
Hi Chris,
this would be a 'multiwire branch circuit'.In a dwelling, the only change would be 210-4(b), which would require a double pole circuit breaker. the rationale, i imagine, is for the protection of the homeowner DIYer,as the normal 120v receptacle would be taken at face value.

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Re: Expecting 120 volts and finding 240 volts #1677 05/20/01 08:56 PM
Joined: Nov 2000
Posts: 123
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doc Offline
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well in my opinion I do not think they should be allowed at allfor my part they are very dangerous esp when trying to tie into and existing grounded conductor and you find out it is a neutral,and yes I agree with you about the warning.
On another forum in 1 week there was 2 different people asking about the outlets not working on bottom but was fine on the top and another had replaced some outlets and had problems
both casses were multi wire circuits that were not installed with the breakers tied together and the other guy thought they were 120 oulets and had no idea to cut the brass link


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Re: Expecting 120 volts and finding 240 volts #1678 05/21/01 07:02 AM
Joined: Mar 2001
Posts: 2,056
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Redsy Offline
Member
2 separate duplex receptacles in the same box do not seem to require a 2-pole breaker. Only if 2 halves on a single yoke are split. There are advantages to multi-wire ckts. though. Less voltage drop, less material cost, less box fill. Obviously, safety comes first, but this is sometimes a competitive game. Always be aware.(EASIER SAID THAN DONE)

Re: Expecting 120 volts and finding 240 volts #1679 05/21/01 03:16 PM
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sparky Offline
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Redsy;
only if on the same yolk!
thanks for the reminder..
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Re: Expecting 120 volts and finding 240 volts #1680 05/21/01 05:05 PM
Joined: May 2001
Posts: 160
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Chris Rudolph Offline OP
Member
Sparky,Doc and Redsy,
Thanks for the reply.

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Re: Expecting 120 volts and finding 240 volts #1681 05/21/01 05:07 PM
Joined: Jan 2001
Posts: 1,044
Tom Offline
Member
Chris,

This is not much of a safety issue or it would likely have been changed in the code by now.

First off, only qualified persons should be working on an electrical system. Henry Homeowner isn't qualified & this trade is not a hobby.

If you are a qualified person, you should know all about multi-wire circuits & you shouldn't be working on them hot with the possible exception of taking a measurement.

What box would you require the 240 volt sign on? If it is a warning sign put on the panelboard, this might not be a bad idea, perhaps you could submit a proposal for the 2005 code cycle.

Tom


Few things are harder to put up with than the annoyance of a good example.
Re: Expecting 120 volts and finding 240 volts #1682 05/21/01 05:48 PM
Joined: May 2001
Posts: 160
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Chris Rudolph Offline OP
Member
Tom,
Thanks for the reply.I was thinking about a stick on label in side a single or more ganged box just hoping that Henry homeowner would give pause and immediately replace the cover plate.It would also serve as a reminder to us folks that have senior moments now and then.
Chris


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