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#1675 - 05/20/01 07:52 PM Expecting 120 volts and finding 240 volts  
Chris Rudolph  Offline
Member
Joined: May 2001
Posts: 160
Winter Park,Fl USA
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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#1676 - 05/20/01 08:05 PM Re: Expecting 120 volts and finding 240 volts  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,311
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.

[Linked Image]


#1677 - 05/20/01 08:56 PM Re: Expecting 120 volts and finding 240 volts  
doc  Offline
Member
Joined: Nov 2000
Posts: 123
Texas
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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#1678 - 05/21/01 07:02 AM Re: Expecting 120 volts and finding 240 volts  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
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)


#1679 - 05/21/01 03:16 PM Re: Expecting 120 volts and finding 240 volts  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,311
Redsy;
only if on the same yolk!
thanks for the reminder..
[Linked Image]


#1680 - 05/21/01 05:05 PM Re: Expecting 120 volts and finding 240 volts  
Chris Rudolph  Offline
Member
Joined: May 2001
Posts: 160
Winter Park,Fl USA
Sparky,Doc and Redsy,
Thanks for the reply.

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

#1682 - 05/21/01 05:48 PM Re: Expecting 120 volts and finding 240 volts  
Chris Rudolph  Offline
Member
Joined: May 2001
Posts: 160
Winter Park,Fl USA
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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