electrics

[gdb]

not sure where to post this one, but here goes anyway....

an old electric circuit is being ripped out. (basically just one long wire which is no longer required but is in the way).

the fuses are off. the wires have been tested with a circuit tester and they show the thing to be dead.

i cut through the cable.

the earth breaker in the fusebox pops.

how is this possible when the cable is dead? (it's still wired up in the fusebox but, as i said, the fuses are off and theres no sign of positive charge.....

[StripyPixieSocks]

I think it's because it may be still connected to an earth and you have broken the earth circuit thus blowing a fuse in your RCB Unit

Basically it's joining something to earth and the circuit registers a sudden change in resistance when you cut it and is protecting itself.

Because you have an RCB unit, you need make sure it is disconnected at the other end (as it is definitely still connected somewhere) before you cut it.

Edit - I think it may be connected to the earth within the fusebox and the box itself should be earthed so you need to disconnect it from these to stop it tripping the fuse when you cut it!

[pumpy]

Even tho' the wire is "dead", if the earth-conductor & the neutral wire are still connected at the consumer unit, then by cutting the cable,you probably created a "short" between these two wires. This will be detected by the trip (R.C.D.) which will then activate. In future,if you not only switch off the cicuit breaker, but also disconnect the neutral, then will avoid nuisance tripping. It's always a good idea to leave the earth connected until all work is finished. Conversely, when wiring-in a new circuit, always connect the earth-wire first, for safety (& a good habit to get into). Hope this helps.

[gdb]

Pumpy and Pixie

Thanks for that. I think you must be right.

I would never have imagined it work like that, but you live and learn. (Though with electrics, it's better to learn first.....)