How to wire up garage RCD

Lisapete · 27 Dec 2014 at 15:16

Bought this http://www.screwfix.com/p/bg-garage...a-rcd-dual-6a-32a-mcb/68849?_requestid=150702

Looks like this

Where does the power supply in go?

I've worked this bit out

I got a 4 way bus bar to go across the bottom from what I can see.

Traffic_Warden · 27 Dec 2014 at 17:24

Here is a quick example

supply goes into top of RCD, L for Live, N for Neutral, your earth core into the earth bar

then a example of how a circuit would go into the MCB, just follow suit after that (ofcourse you will have two cables going into the 32A breaker/bars for a ring final circuit, just put one set of cores for an example of where they go)

JohnnyG · 27 Dec 2014 at 19:24

Considering the feed you're using for the garage is already RCD protected why are you using another one in the garage?
And if it's still coming off the RCD protected interior sockets you could be opening yourself up to no end of annoying faults, outdoor electrics are notorious for earth faults, especially when DIYed.
By the way, use brown sleeving in future not red.
There's a reason the quotes you got for this job were quite high and that's because someone was going to do it properly.

Traffic_Warden · 27 Dec 2014 at 21:12

Am I missing something here? I don't see anything about inside RCD or high quotes to do this?

If it is RCD'ed inside (rcd or rcbo?), make sure this one is of a lower mA trip time, so anything inside of the garage trips it's RCD before the RCD/rcbo inside to avoid problems.

JohnnyG · 27 Dec 2014 at 21:22

This thread will give you a bit of insight - http://forums.overclockers.co.uk/showthread.php?t=18590091
No discrimination or S types, red sleeving on lines, SWA won't be earthed, no load calcs etc.
I'm all for people doing their own work (whatever that may be) but some things are genuinely above DIYer's.

Traffic_Warden · 27 Dec 2014 at 21:48

So what's actually controlling this SWA going out to the garage? As there's a 4x4 box on the wall with only one T+E cable going into it and a SWA coming out. Where does the T+E come from before connecting into the 4x4 box?

Traffic_Warden · 27 Dec 2014 at 21:51

Ok I found the answer to that....This is probably just a 2.5mm T+E from one of the kitchen sockets? If so then please do not feed the garage from this, it needs to be a seperate feed from the house C/U and done properly

JohnnyG · 27 Dec 2014 at 21:54

Too late for good advice I think...

Lisapete · 28 Dec 2014 at 00:12

Traffic_Warden said:
Here is a quick example

supply goes into top of RCD, L for Live, N for Neutral, your earth core into the earth bar

then a example of how a circuit would go into the MCB, just follow suit after that (ofcourse you will have two cables going into the 32A breaker/bars for a ring final circuit, just put one set of cores for an example of where they go)

Thank you. As I come back too read this I just found this, but the bottom of it wrong correct?

The house is a new build, the electrical install as you can see was done by and signed off by Clarkson Evans so do not point the finger at me! All 50 homes of the same model as mine has this exact setup for the power to the garage. Other homes here are not so pretty on the install.

Original setup in the garage was radial and the tumble dryer blew that up once already.

The reason I've had quote not just for this but other stuff being high is due to the location, a 4 bed house here costs over £400K now. Every trades man that's been here, other homes around here are wacking the prices up. I get them to quote for the same job at a different house, exactly the same job it's 10 times cheaper.

I didn't have brown to use and needed it to be done there and then, it's been corrected about a week latter to conform to regs.

Thanks

Tesla · 28 Dec 2014 at 00:28

Is the entire garage powered by a single 2.5mm t&e protected by a 32a mcb or am I mistaken?

Traffic_Warden · 28 Dec 2014 at 00:39

Busbar is all you need to complete this now, it goes between the bottom "L" of the RCD, and all the MCB's at the bottom also. (See below spoiler)

Where does the 2.5 come from? This needs to be your first concern IMO. It needs to be traced and find out where it comes from/what it's connected too.

If you take the front cover off the C/U and see if there's three brown cores connected into the top of the MCB that powers it, or just two. If it's two then it would indicate that there's a switch somewhere (in the kitchen?) for the garage supply, or there's a junction box behind the wall (which I wouldn't be inclined to be the case, as it's a new build). If you take the cover off and there's three brown cores in the same MCB, I would think that one of them three cores goes straight to that outside 4x4 junction box that the SWA is connected into.

Lisapete · 28 Dec 2014 at 00:51

Traffic_Warden said:
Busbar is all you need to complete this now, it goes between the bottom "L" of the RCD, and all the MCB's at the bottom also. (See below spoiler)

Where does the 2.5 come from? This needs to be your first concern IMO. It needs to be traced and find out where it comes from/what it's connected too.

If you take the front cover off the C/U and see if there's three brown cores connected into the top of the MCB that powers it, or just two. If it's two then it would indicate that there's a switch somewhere (in the kitchen?) for the garage supply, or there's a junction box behind the wall (which I wouldn't be inclined to be the case, as it's a new build). If you take the cover off and there's three brown cores in the same MCB, I would think that one of them three cores goes straight to that outside 4x4 junction box that the SWA is connected into.

I though it was like that, thanks.

As per this photo the garage feed if fed off the kitchen which is on a 32A. I have no idea where the T&E comes from kitchen wise.

http://i59.tinypic.com/2e52ix4.jpg

I'll open the box tomorrow if wanted

Lisapete · 28 Dec 2014 at 12:30

how to do a screen shot

That 6A on the far right is for the security lights outside which could be removed. This would then give me dual spacing for an isolater.

I think your right that the current feed must come off down the back. I could check the sockets for a 3rd tail which would be the feed. Only snag is to rewire a proper feed over means new slabs down the back which I think she wants doing

Traffic_Warden · 28 Dec 2014 at 14:04

Yeah that looks all in order, as you suggest may be worth a shot looking for the third cable in the kitchen sockets, but it's entirely upto yourself, I can spend hours finding cables and then at the end of it none the wiser, it could be in a junction box behind the wall for all we know

Lisapete · 28 Dec 2014 at 17:16

Traffic_Warden said:
Yeah that looks all in order, as you suggest may be worth a shot looking for the third cable in the kitchen sockets, but it's entirely upto yourself, I can spend hours finding cables and then at the end of it none the wiser, it could be in a junction box behind the wall for all we know

So it's the 2nd 32A MCB on the right next too the RCD.

I'll check where I think it is but as for junction box it' likely to be hidden in the wall which is a no go there and then.

What's my options?

lemonkettaz · 28 Dec 2014 at 17:29

That consumer unit looks scruffy

In the main consumer unit in the house have an RCBO feeding the outside garage consumer unit, then have all circuits in the garage protected via an RCD isolator.

Dont run a whole new garage consumer unit from the 32a ring main in the house.

Basically do it properly of dont bother

Traffic_Warden · 28 Dec 2014 at 17:36

As above is the best option, but if you want to continue doing it the same way, look below

Your best option is to do exacly what you suggested and take off a socket at a time and look for three cables at one socket in the kitchen.

If you can not find it then it will work if you connect it all up the way it is, but I would be concerned as to how much power you are drawing from the garage at the same time as using appliances in the kitchen, if they both add up to more then 32A (depending on how much more) then it will only be a matter of time before the MCB trips off randomly (due to it being over loaded). But, having said that if it's just a tv or radio in the garage and a few lights and maybe a drill etc then it's not going to make much odds.

ZG002 · 28 Dec 2014 at 17:55

That board is a right mess for something fairly new, it doesn't suprise me that they have half arsed the supply to garage. Where is the point in having a second RCD in the garage? You are protected by the one at the CU. Running something like 7 sockets (tumble dryer also) and lighting from a single spur isn't really good practice lol.

Lisapete · 28 Dec 2014 at 18:21

online photo sharing

So all that's left is power in.

House is 6 years old if it helps.

The garage has 2 strip lights, tumble dryer. Sometimes I'll be using power tools. Just your normal diy stuff (chop saw, bench grinder, bench sander, drill press, band saw). I'll also have a 27" screen, Intel NUC, speakers in there.

I'll see if I can find the feed. If it will work then great. When the question of repaving the back comes up maybe a cabl directly from the meter?

I wanted a smart looking setup and thought it was sensible.

ZG002 · 28 Dec 2014 at 18:30

It's just a fair amount of equipment to be running from a spur! Something that wasn't actually allowed back in 16th edition (which your cu is wired too)

Running a cable from the CU to garage is a much much better job and is how any electrician would price the job.