RCD Socket Install Problem.

[Farleigh]

Removed a double socket in the garage, extended the cable via a junction box and connected up an RCD two gang metal clad socket. Turned the power on, made live the socket and it trip the main RCD protected switch on the fuse board. Totally confused why this has happened. Is the socket faulty? Have I somehow wired it wrong? Are the electrics in the garage shot?

 

[flameport]

If you have an RCD already, you do not need to add a socket with another one.

made live the socket

by doing what? If it involved pressing the test button on the front, then yes - plenty of those will trip any upstream RCDs as the test function simulates a fault.

 

[Farleigh]

I guess the reasons for it was to connect my power tools and if it tripped it would only trip the socket not everything else.

 

[ban-all-sheds]

by doing what? If it involved pressing the test button on the front, then yes - plenty of those will trip any upstream RCDs as the test function simulates a fault.

IME pressing the test button on RCD sockets does not "make them live".

 

[ban-all-sheds]

I guess the reasons for it was to connect my power tools and if it tripped it would only trip the socket not everything else.

No guarantee - a fault might trip the socket or the main RCD, or both.

 

[Farleigh]

Ban all sheds - Does that mean I should have the RCD socket installed?

 

[omega015]

If its already on an RCD protected circuit then there is no need for a secondary RCD. You can either remove the RCD socket and replace with an ordinary socket or leave it as it is, knowing that 1 or both RCDs might trip under a fault condition.

 

[Farleigh]

Ideally I'd like to have the RCD socket installed but I don't understand why when wired up it trips the whole circuit when turning the power back on.

 

[omega015]

So it trips as soon as:
You reset the RCD on your consumer unit? (faulty cable/work done on your junction box to extend the cable or the socket/wiring at the socket)
Or
When you press the reset button on the socket? (faulty socket or what's plugged into it)
Or
When you pressed the test button? (This is normal, expect one or both RCDs to trip when testing at the socket or a fault to something plugged in)

 

[omega015]

If its not the last scenario, please can you switch off the garage electrics and take a photo of the junction box wiring and the back of the rcd socket and post a link/upload (just in case there is something obviously wrong that we can point out).

 

[ban-all-sheds]

Turned the power on, made live the socket

Is there a difference between those two?

You turn the power on, but the socket is not live? What do you then do to make it live?

 

[ban-all-sheds]

Ban all sheds - Does that mean I should have the RCD socket installed?

It's a bit belt-and-braces if you've got one in the CU, as it won't necessarily do what you thought it would, i.e. ensure that the CU one does not trip if there's a fault with an appliance plugged into the RCD socket.

I've seen people argue in favour of such redundancy, but never seen them argue in favour of having 2 RCDs in series in the CU, so...

However - if it's a non-latching, or active, RCD socket that can be handy for tools and workshops etc, as it will trip on loss of power, and stay tripped when power is restored, which might be a useful safety feature as it means that tools, heaters, whatever, don't start up again when power is restored. I guess how useful depends on how likely you are to wander off leaving tools latched on when there's a power cut.

 

[securespark]

Best scenario would be to put the RCD socket in the garage on a non-RCD circuit but it depends where and how the cable has been run to the garage and what type it is.

 

[Farleigh]

So cable is run from a spur from the house to the garage. Goes into a consumer unit in garage and then to the sockets. The RCD double socket was bought from Toolstation. Pictures of junction box and socket wiring.

 

[endecotp]

I don't see anything wrong with the wiring in your photos, and I don't think your main RCD should trip in that case. You should investigate and find out why it does.

I'd start by disconnecting the RCD socket; that will confirm if the problem is in the new cable or junction box (nail through the wire?)

If that is OK, I'd try reconnecting the wires to the RCD socket one at a time (E then N then L) and checking what happens each time.