Regacy

Just tripped the fuse box and I can’t understand why. (Other than the fact I’m a complete amateur)
Wiring in an additional socket in the garage, modern house so trip switches not fuses.
Main box in the house, additional box in the garage.
Box in the garage has 2 fuses in it, on for the lights one for the existing socket.
I’ve added a junction box into the existing wire running to the existing socket.
Wired up the new socket ran the wire up to the existing wire and into the junction box.
Having pulled the fuse for the socket wire (and plugged a light into it to make sure it’s dead) I cut the wire and……..
Darkness all over the house.
Shut down the power for the rest of the house, wired it in to the junction box, turned the power back on and it’s all ok now.
So why did it trip when I cut the wire?
And how come I didn’t get a shock?

David_Wallis

The main RCD probably tripped measuring a Neutral to Earth Fault.

hawkthescoobslayer

depends on what mA the breaker is a trip switch DOES NOT stop you getting a shock it limits the time and therefore severity of it

a 30mA 60 mSec breaker will only require 30/1000's of an amp from either live to earth or neutral to trip and will only take 60/1000's of a second to trip you probably cut through the live and was touching an earth causing the system to trip


no harm done

Paul

Adrian F

David's right when you cut the wire you probably touched the neutral to the CPC (Earth) and the RCD decided that a fault was present. The pulling of the fuse (Triping off the MCB) only isolates the phase (live) conductor not both . You would have to turn the main switch on the DB in the garage off (Double Pole isolation) whilst doing this work to be sure of not taking out the RCD in the house.

Regacy

Thank you. I'm reassured now.
I should have isolated the garage power, but then I couldn't see what I was doing in the dark.
Gave Mrs R a shock anyway when the power went down inside, she came out like a shot expecting me to be frazzled.
All working ok now though.
R