Isolate circuit or disconnect all power when changing sockets

[diydave99]

Hi, I'm in a modern house with new electrics. I was working on a socket and moved the circuit breaker to off before starting on that particular ring. However the RCD tripped, I guess because I bridged earth and neutral when cutting the wire.

So what should I have done, flick the big switch on the consumer unit to remove all power to the house, or is just isolating the circuit as I did sound ?

Thanks in advance.

Dave

 

[Iggifer]

Proper procedure is to disconnect both the line and the neutral, so opening the main switch or the RCD will isolate them both.

In practice, most people will just isolate the fuse/MCB as it’s not always practical to isolate them both, and people are lazy

You’re likely fine just isolating the MCB, but I can’t recommend it, as the neutral can become live if there’s a fault.

 

[diydave99]

Proper procedure is to disconnect both the line and the neutral, so opening the main switch or the RCD will isolate them both.

In practice, most people will just isolate the fuse/MCB as it’s not always practical to isolate them both, and people are lazy

You’re likely fine just isolating the MCB, but I can’t recommend it, as the neutral can become live if there’s a fault.

Appreciate the swift reply. Many thanks.

 

[Echo the husky]

Also check the power is actually off at every point you work on, just because the first 3 sockets in a room were dead, doesn't mean the fourth one will be.

 

[Iggifer]

Also check the power is actually off at every point you work on, just because the first 3 sockets in a room were dead, doesn't mean the fourth one will be.

Quite! Once did a test on a house that had 3 socket circuits per room. Was done for redundancy when the place was wired by all accounts. Made for hard testing!

 

[ban-all-sheds]

As you've discovered, with only the MCB off you'll trip the RCD when you short N & E.

And there's a good chance you'll do that again when fiddling with the new sockets.

 

[John D v2.0]

I usually turn off the MCB, disconnect the l and n at the cu and secure them. I'm going to need them disconnected anyway in order to do the ir testing later so it's no hassle. Reduces the chance of anything becoming live while I'm working too.