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#144408 - 11/21/05 02:09 PM Lighting circuit Neutral
Uppeydog Offline
Member

Registered: 07/09/04
Posts: 64
Loc: Loch Lomond
Brain Teaser (well it is for me!):

Cieling rose; Switched Live To Earth or Neutral = 240V..OK.

1st Neutral Black To Earth = 0V..OK.

Another Black 2nd(Supossed Neutral)Joined to 1st Neutral. When separated from 1st Neutral reads To earth = 240V...?
and to Switched Live (on) 0V.

When joind back to 1st Neutral reads To Switched Live = 240V. and to earth 0V.

Howcome This supposed Neutral carries 240V when separated from other Neutral?

Don't shout at me this for my neighbour!!
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#144409 - 11/21/05 03:17 PM Re: Lighting circuit Neutral
aussie240 Offline
Member

Registered: 07/06/05
Posts: 221
Loc: Blue Mountains, NSW, Australia
Hard to visualise without a diagram....what is this other '240v neutral' connected to?
Are you using a high impedance digital voltmeter? If so the capacitance from this neutral to an active wire could be high enough to produce 240v on no load....especially if the neutral is part of a long length of twin cable.
If this '240v neutral' is the return for some other load which is switched on then obvioulsy it will be at 240v when disconnected.

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#144410 - 11/21/05 03:47 PM Re: Lighting circuit Neutral
Uppeydog Offline
Member

Registered: 07/09/04
Posts: 64
Loc: Loch Lomond
Good one Aussie,
He's just knocked on my door, as someone tried to nick his cherry picker!!

He told me he's got it sorted; it was the neutral from the room next door. He had the switch next door taped down in the off position, but his offsider turned it on at the back door!!!(Two - Way Switched!!!)

I won't tell him you called him a stupid "POME B"... ('Cause he's 6'4"!!!)

Cheers. 2Rivers (Katherine & South Aligator)
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#144411 - 11/22/05 08:16 PM Re: Lighting circuit Neutral
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
This particular thing has been known to kill the odd Electrician working at a switch-board.
If a Neutral loses its reference to it's usual busbar, it then becomes a Phase conductor.
This is of course assuming that the circuit is still energised and the switch is on.
Leaning you arm up against the metal side of a switch-board body and holding a wire you thought was a Neutral before can be the easy way to get a fatal hand-to-hand shock.
Be careful around them Neutrals!.
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#144412 - 11/23/05 01:51 PM Re: Lighting circuit Neutral
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2343
Loc: Vienna, Austria
That's why I like our 1+N circuit breakers so much!!! You can't switch off the phase w/o the neutral.

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#144413 - 11/25/05 01:28 AM Re: Lighting circuit Neutral
Uppeydog Offline
Member

Registered: 07/09/04
Posts: 64
Loc: Loch Lomond
Thanks for those replies!

What had happened is the cieling had come down. Jim rang me & explianed the above.

The first thing I said was to turn off the lighting circuit & use table lamps plugged into the wall sockets for light.

So they obviously just turned off the light switches & taped them down. Not awear the kitchen fluro was double-switched !! Meanwhile his mate had come in the back door, turned on the fluro (which did not light because the neutral loop was disconnected in the next room)so he probably left it on, which energised the open neutral in the next room!!
At least they were awear of the "live" conductor.

Just goes to show the juction box set up is a lot safer in these situations, where the loop remains intact, & just each fitting can be removed (with the supply off of course!) but you never know what's happened in the past ie. some one may have decided to connect in a neutral from a different circuit. (Good old multimeter saves the day again!!)

Texas Ranger: are they (L+N) the standard cicuit breakers in USA?

Cheers, 2Rivers.
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#144414 - 11/25/05 02:35 AM Re: Lighting circuit Neutral
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
People sometimes don't seem to realize that the neutral is only at (or near) ground potential so long as it is connected to the supply neutral. As soon as there's a break.....

 Quote:
are they (L+N) the standard cicuit breakers in USA?


No, the U.S. normally just switches the phase(s), as here. Even the main on a panel doesn't open the neutral. Texas-Ranger is in Austria.

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#144415 - 11/26/05 08:39 AM Re: Lighting circuit Neutral
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2343
Loc: Vienna, Austria
 Quote:
Texas Ranger: are they (L+N) the standard cicuit breakers in USA?

As far as I'm aware of 1+N breakers are only commonly used in Austria, France, Belgium and some Eastern European countries.

Re: my nick: we got international TV here too

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#144416 - 11/26/05 08:47 AM Re: Lighting circuit Neutral
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
So there's no truth to the ECN rumor that you're related to one of these guys then, kemo-sabe?




[This message has been edited by pauluk (edited 11-26-2005).]

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#144417 - 11/26/05 03:55 PM Re: Lighting circuit Neutral
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2343
Loc: Vienna, Austria
My nick name is my only connection to them...

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