Replacing Outhouse RCD UNit - Wiring Help

[PadoDIY]

Hey all,

Just looking for a bit of confirmation if possible. I am replacing an end of life unit with a new Garage Kit RCD that will be housing a 2 way socket and a light. All the existing cabling is in place and it is just to cable up the new unit. I have attached a diagram but would just like it if someone could check it for me.

I have a sparky coming round tomorrow to PAT test and certify it for me.

Any suggestions for corrections/improvements would be much appreciated.

Thanks,

PadoDIY

Untitled

• PadoDIY
• 15 Aug 2012
• 1

 

[securespark]

What is the rating of the supply to the garage?

What size cable will be attached to that 32A MCB?

Have you got any pipework in the garage?

What is your supply type?

 

[JohnW2]

Any suggestions for corrections/improvements would be much appreciated.

In addition to all the other matters which need to be consdiered (per securespark's post), the wiring you've indicated at the bopttom of the RCD/MCBs is incorrect. It should not extend to the neutral of the RCD (i.e. the right-most bit shouldn't be there), and the remaining three connections should be by a busbar (a piece of metal which should have been suppleid by the kit), not wires. Others may well have more general comments about the work you are proposing to undertake.

Kind Regards, John

 

[PadoDIY]

Hi John, sorry i should have said in my description that the blue wiring at the bottom is a busbar that was supplied with the unit. I will move the busbar one along to the left.
Other than that is everything else correct? As i say all the existing cabling is there and there are no extra loads being added. It is just to replace the existing unit.

Securespark,

A 2.4mm TE cable will be attached to the 32A MCB, garage has no pipework and I am unsure of the supply type?

Thanks.

 

[JohnW2]

Hi John, sorry i should have said in my description that the blue wiring at the bottom is a busbar that was supplied with the unit. I will move the busbar one along to the left.

Fair enough, and you certainly would need to make that change if you don't want a big bang!

Other than that is everything else correct?

In terms of the CU wiring, I can't see anything else wrong.

However, as others are implying, an electrician would have to consider a number of other things in order to ensure (and certify) that the installation was safe and compliant with regulations. For example, where is the 'mains' coming from, through what cable and what (MCB or whatever) is protecting that cable at the other end?

Kind Regards, John

 

[PadoDIY]

Hi John,

the mains is coming directly from the main distribution board. The previous installation was certified to the garage so all other requirements have been met. Once i have the new unit installed it will be checked by the sparky tomorrow so i am sure he will highlight any other concerns.


Thanks for your help.

 

[JohnW2]

the mains is coming directly from the main distribution board. The previous installation was certified to the garage so all other requirements have been met. Once i have the new unit installed it will be checked by the sparky tomorrow so i am sure he will highlight any other concerns.

Indeed, I would imagine that he will. One thing to bear in mind is that regulations are evolving/changing all the time, so that fact that the installation was certified as compliant in the past does not guarantee that it is compliant with current regulations. The electrician will (should!) certainly take an interest in exactly where in the main distribution board that cable is coming from, what is protecting it, what route it follows and what size the cable is. He will (should) also be interested in the things (sockets/lights etc.) being supplied by the new CU (and the cables supplying them) and, as has been implied, the supply type and earthing/bonding arrangements.

Kind Regards, John

 

[securespark]

Hi John, sorry i should have said in my description that the blue wiring at the bottom is a busbar that was supplied with the unit. I will move the busbar one along to the left.
Other than that is everything else correct? As i say all the existing cabling is there and there are no extra loads being added. It is just to replace the existing unit.

Securespark,

A 2.4mm TE cable will be attached to the 32A MCB, garage has no pipework and I am unsure of the supply type?

Thanks.

What is supplying the incoming cable of the shed CU and how big is it?

If it's from a 13A fused spur or 16/20A MCB, then the 32A MCB is useless and there is no discrimination.

If there is just one or two sockets, I would downgrade the 32A to a 20A. If you need to run more appliances, I would uprate the cable.

 

[Taylortwocities]

You obviously did not like the responses that you got on "another" forum?
At least the busbar is now at the bottom and not across the top of the MCBs as in your previous design

But the same advice will apply here.

If you have a length of 2.5mm² cable going to your single socket then that 32amp MCB is too big. It needs to be 20 or 16amp. Or you'll have to install bigger cable.

This is notifiable work. SO I hope your electrician is prepared to lie to his registration body and say that this is is own work.

Last point. Why on earth will your electrician need to

PAT test

this? It does not look portable to me?

 

[The Dentist]

The incoming neutral is incorrect

Edit: scrub that, thought the existing N was entering the RCB at the top

 

[ban-all-sheds]

You obviously did not like the responses that you got on "another" forum?

Got a link?

 

[Taylortwocities]

Sure thing

 

[JohnW2]

Sure thing

Some things appear to be contagious ....

Quite frankly the OP has asked a question....Why?...because he's not sure. ... All the OP needed telling was that he is out of his depth,and the dangers and legality of what he is doing. There was no need for the abuse and sarcasm, with the notable exception of 1shortcircuits input and a few others , reading through this thread I'm almost ashamed to be associated with this forum.

Where have I read very similar things, I wonder?

Kind Regards, John

 

[JohnW2]

For example, where is the 'mains' coming from, through what cable and what (MCB or whatever) is protecting that cable at the other end?

The electrician will (should!) certainly take an interest in exactly where in the main distribution board that cable is coming from, what is protecting it, what route it follows and what size the cable is.

Kind Regards, John