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.
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"!!!)
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!.
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?