Fault Finding

[Finneganjp]

Hello,
I recently built my garden shed and now im trying to wire it, unfortunatly i have a snag, it doesnt seem to be working for me. I will try to explain what i have done so here goes.

I have burried 4 core swa cable from the house to the shed.
In the shed the swa is running straight into a new consumer unit which is feeding two lights and two sockets at the moment. The set up is - 63a isolation switch, 10a lights, 63a RDC feeding 20a sockets
The core swa was given to me by a budy so hence the four core (no three core available). I have doubled up on two of the cores to give me a live.

In the shed consumer unit the the live is running into the underneath of a 63a isolation switch, the neutral goes to its own buss bar and same with the earth. From the top of the isolation switch the live comes out and feeds the underside of the 10a mcb for the lights and out of the top comes the live that feeds the ligths. The neutral and earth go the their respective buss bars.
From the underside of the 10a mcb for lights the live is feeding the underside of the 63a RCD and the live out the top feeds the underside of the 20a for the sockets and out of the top of this the live feeds the sockets. The neutral from the sockets comes in the top of the RCD and out the bottom to the neutral busbar. The earth from the sockets goes straight to the earth bussbar.

In the house consumer i have the swa cable brought into the house and and connected to 6mm2 t&e cable and that is running into my house side consumer unit.
Within the consumer unit i brought the live to the top of the 63a isloation switch, the neutral to the socket side neutral bussbar and the earth to the earth bussbar. There are two neutral bars, one for the lights etc and one for the sockets running off an elcb.

I then tried it, the lights seem to work but when i plug something into the
sockets and try it the shed rcd trips.
I have one of these socket testers that you plug in and its telling me that i have an earth fault. (what does this mean?)
Can any one see what the problem may be?
All help appriciated....

 

[comms]

Just had a quick scan one point straight away, sounds like your neutral supply from house consumer unit to shed final circuits can only be isolated by turning off the main isolation switch of the house c/u ? should be through double pole main isolation switch in the shed consumer unit.

 

[Finneganjp]

Hello Comms,
Point taken. Could that account for why my sockets dont work?

 

[slippyr4]

From the underside of the 10a mcb for lights the live is feeding the underside of the 63a RCD

ok..

and the live out the top

out the top of what? the MCB or the RCD?

feeds the underside of the 20a for the sockets and out of the top of this the live feeds the sockets

I'm really confused as to what you've connected to what. You have your RCD in between the live connections for the lighting and the sockets??

Did you connect the appropriate neutral connections to the RCD?

It sounds dangerous. I'd leave this disconnected until you're certain you've got it right. (disconnect at the house CU).

BTW, SWA armour is normally used for earth - hence you needed 2 core SWA, not 3. Doubling up conductors is not a very good idea for a multitude of reasons - but this is probably not your issue here.

 

[slippyr4]

The first picture on this page may help you http://www.diydoctor.org.uk/projects/consumer_unit.htm

In a nutshell, your incoming SWA L&N should be wired to the incoming side of a Double Pole isolator switch.

The output neutral of the DP Isolator should go the the first neutral connector block (if you have a split load CU), or direct to the neutral incomer of the RCD. The Live out from the DP isolator goes to the RCD incoming live. The RCD outgoing neutral goes to the second neutral connector block (if you have a split load CU) or to the only neutral block (if you have a single sided CU).

Connect your bus bar to the outgoing live on the RCD and to your lighting and sockets MCB's. Connect your lighting and sockets cables - live to the live out on the appropriate MCB, and neutral to the neutral block that you connected the RCD to.

All earths go to the common earth block.

If you still are not sure then please get an electrician in.

 

[Finneganjp]

and the live out the top

out the top of what? the MCB or the RCD?
RCD

feeds the underside of the 20a for the sockets and out of the top of this the live feeds the sockets

I'm really confused as to what you've connected to what. You have your RCD in between the live connections for the lighting and the sockets??
The sockets are on the rcd side not the lights.

Did you connect the appropriate neutral connections to the RCD?
Yes

 

[ban-all-sheds]

Post photos, or a diagram of what you've done - making sure it's a diagram of what you've done, not what you planned to do or think you've done...

 

[Finneganjp]

Il draw up a wiring diagram and post it, thanks.

 

[Adam_151]

The way I picture it, it sounds like he has got the live supply and load one way round on the rcd, and the neutral supply and load the other way around.

but yes a diagram would help a great deal

 

[Finneganjp]

Hello again,
Sorry for taking so long to get back to ye all.
Basically the lights work but the RCD keeps tripping the sockets, anyone spot anything obvious?
http://imagesx.net/082005/677.jpg

 

[Qedelec]

Drawing looks ok if a little difficult to see.
The earth fault you described from your first post suggests you have a short to earth, probably from the neutral.

Disconnect the sockets cable and put a meter between all conductors, i.e. Phase-Neutral, Phase-Earth and Neutral-Earth.

This should have been identified when you did the insulation tests before energising the circuit.

 

[Finneganjp]

I have tested for continuity between all cables and it all seems in order???

 

[Qedelec]

Checking for continuiy will not find the fault.

Insulation tests requre 500V @ 1mA and must measure in excess of 1/2MegOhm.
Buy, borrow or steal an insulation tester.

Oh and don't hold the probes when you press the button!!