Adding a 2 way unit to a garage

Mfctitch · Feb 18, 2013

Evening everyone

I have been asked to price to add some more sockets and lights to a garage plus a few out side sockets.
now the garage already had a supply from the house via SWA cabling which just feeds a socket and the lights via a fused switched spur.
now the consumer unit in the house is an old "Ashley & Rock" with Supasafe MCB's. with blue writing if that helps the whole lot is protected with one main RCD.

Now for my question.
I know that I can fit just a 2 way unit but I was thinking that with more sockets and some of them outside it would be better to fit an RCD in the garage.
but I need this to trip before the house RCD trips so any suggestions would be great.

Thanks for all suggestions

partypest · Feb 19, 2013

You're welcome mate. There are plenty of Electrical Trainee out there who have actually been doing it for years and have decided to be legit and do it properly. I know of some kitchen and bathroom people who quote this Reg and that Reg at me when they haven't got a clue about Ze or U or I or W. Good for you for going legit and I hope it pays off. Back to that garage supply though, you have now learned that some jobs need a bit more note taking and fact finding. This forum should be an excellent sounding board for ideas, but there are one or two grumpy old men and I hope they haven't put you off. My two pennies, before any further facts from you, would be to separate the supply to the garage on to it's own CU and RCD at the CU in the garage. If you're 'full scope' on NICEIC, you can sign this one off, if you're 'limited scope', you can't, as you're changing the protective device. I would also be very sure that you establish all the facts about the supply cable to the garage. Measure its resistance, compare that to what it should be for a cable of that estimated length etc. there could be joins/different cable etc. I'm glad to hear you want to do it right, and the only way to do that, is to be 100% sure with what you're connecting to, particularly with older installs. Good luck.

Mfctitch · Feb 19, 2013

Murdoch said:
The only thing I'll add after post 59 is that if your expertise is kitchens and bathrooms why are you messing with a garage supply?

Being a Electrical Trainee is irrelevent imho, but if you are only doing the "odd" electrical job then to get up to speed with the plethora of different installations, and styles and types of installs could take you decades.

Thanks for reply I do slightly more than the odd electrical job. but when you are someone's house and they offer you a job that you can do why turn it down?
As has been said before I could have just added a 2 way board and been done with it.
But I would rather add a bit more protection.

I do how ever take your point about it being a steep learning curve and there will be times when I will have to ask for help, be it from this forum or from other electricians that I know.

eganelectrical · Feb 19, 2013

Just a note off myself wire puller I should have explained in post 3 that adding the earth rod was additional to the earth in the swa. I was told this was good practice and as for helping discrimination I was told this would help but maybe that's only for TT. If I'm wrong then I am open for people to comment but don't appreciate the way some of the comments "Murdoch" come across! I haven't done domestic for a while so have to think about things, some of you it's 2nd nature. There's no need to be arsy about things as we all can help each other!! I have only come on here to help get my mind back into domestic etc. it's nice to keep on top of things.
Anyway about the install.
Are domestic final circuits not allowed 100mA protection? I thought this was ok because people who put 16th ed ccu into houses change the up front rcd to 100mA which then protects the non rcd side if the ccu does it not??
What are the thoughts on the other chaos comments on 40ms rcd?
Don't want to confuse the matter here and I'm not saying what's right or wrong but people are slating others without giving a proper explanation.
Murdoch advised at the start of this thread not to change anything and slated the idea of a time delay, then later he commented on this should be an option. This has just confused things as far as I am concerned??
Tidy comments appreciated

Engineer54 · Feb 19, 2013

eganelectrical said:
Just a note off myself wire puller I should have explained in post 3 that adding the earth rod was additional to the earth in the swa. I was told this was good practice and as for helping discrimination I was told this would help but maybe that's only for TT. If I'm wrong then I am open for people to comment but don't appreciate the way some of the comments "Murdoch" come across! I haven't done domestic for a while so have to think about things, some of you it's 2nd nature. There's no need to be arsy about things as we all can help each other!! I have only come on here to help get my mind back into domestic etc. it's nice to keep on top of things.
Anyway about the install.
Are domestic final circuits not allowed 100mA protection? I thought this was ok because people who put 16th ed ccu into houses change the up front rcd to 100mA which then protects the non rcd side if the ccu does it not??
What are the thoughts on the other chaos comments on 40ms rcd?
Don't want to confuse the matter here and I'm not saying what's right or wrong but people are slating others without giving a proper explanation.
Murdoch advised at the start of this thread not to change anything and slated the idea of a time delay, then later he commented on this should be an option. This has just confused things as far as I am concerned??
Tidy comments appreciated

Adding an earth rod is good practice on a PME installation, but will do nothing for helping RCD discrimination.
Nothing wrong with 100mA RCD's in a domestic either, so long as tripping times comply etc!! They however shouldn't be used to protect Socket circuits.
S type RCD's are generally used for discrimination to downstream RCD's on TN systems. But shouldn't be used as the sole up-front means of RCD protection for an installation. In other words there should always be a standard RCD(s) downstream.
In TT systems, it's prudent to have an S type up-front on any RCD/RCBO CU for additional protection, in the event of the downstream RCD device's not operating or failing, as your totally relying on the RCD devices, for your earth fault protection in TT systems...

Apologies if i gave the impression of slating you in any earlier posts!! lol!!

eganelectrical · Feb 19, 2013

Appreciate the reply and info mate, thanks. I take it S type is selective? It's got a dial on it?
What about 16th ed ccu's where one side has no rcd? Are they only reliant on the up front rcd??

Engineer54 · Feb 19, 2013

eganelectrical said:
Appreciate the reply and info mate, thanks. I take it S type is selective? It's got a dial on it?
What about 16th ed ccu's where one side has no rcd? Are they only reliant on the up front rcd??

S type = Time delayed, be they either adjustable or factory set!!

Though the 16th ed CU's don't comply with 17th ed, they do not warrant a fail code. The RCD was only required for certain circuits, (sockets etc) so it's basically covering one half that of a modern dual RCD CU. Not really classed as a up-front RCD as it doesn't cover the whole installation!! Think they used to call them a Split CU??

Mfctitch · Feb 20, 2013

new info but I'm afraid it's not looking good.
went back to house tonight and took the cover off the consumer unit.
32A MCB running ring main for upstairs. plus the power for the garage.
Cable looks like 2.5 which is joined on the outside of the house then goes over to the garage.

I hope that the photos help.

As you can see the supply is fused in the garage and then comes off from there.

The customer wants in the garage sockets as follows:
3 double socket just so he can plug an item in without the use of an extension lead
2 single sockets to plug small green house heaters on timers so keep his two cars warm honest.
6 led down lights outside
And outside socket for the lawn mower
and outside socket for Christmas lights.
The run for the house is about 15 metres.
Now I will probably be corrected here but I was looking in the green book and I think the cable can carry 18.5 Amps
And as you can see there is a 13 Amp fused spur which everything comes off.

My question is apart from just running away

Should I leave the fused unit in place as this will protect the cable and come off of that with a two way board which I can then
run a 16 amp for the sockets and a 6amp for the lights.
that way what ever he plugs in if he starts to draw too much the 13amp fuse will go.

Where as if I put a two way board in place of the fused unit he could draw more current than the cable could handle.

Now I understand why I should have looked at the job in more detail before coming to the forum and asking for help.

[ElectriciansForums.net] Adding a 2 way unit to a garage

thomas-1981 · Feb 20, 2013

Should I leave the fused unit in place as this will protect the cable

Read more: http://www.electriciansforums.net/e...adding-2-way-unit-garage-5.html#ixzz2LQtIaAPc

Is this the fcu in the garage? And what cable are you suggesting it's protecting?

Engineer54 · Feb 20, 2013

That cabinet around the CU can be easily replaced for a larger one. To be honest, it should be anyway there isn't any room for air circulation in that tiny cabinet!! So the earth system is a PME, at least now that can be taken into consideration... Going by what you have told us above i think your customs really asking too much from this 2.5mm supply to the garage etc.

Without going too much into detail, this now all depends on if the customer is prepared to pay for what he wants, if he's not then it's a pointless exercise for both you and us to prolificate on the details of what is needed.

Edited.... lol!!

thomas-1981 · Feb 20, 2013

I don't think the fcu supplies the garage, I think it protects the socket and light in the garage. I think the garage is supplied by 2.5mm supplied from the cu.

Engineer54 · Feb 20, 2013

You could be right there!! lol!! So it's still all down to, as to how to achieve discrimination!! And the only sensible way to do that is to change the CU for a so-called high integrity CU, or spend a good amount of time converting the existing CU to suit!!

That FCU wiring looks in a pretty bad way, you can see that the wiring has been squashed/crushed against each other and the front plate, ...among other things!! lol!!

R G · Feb 20, 2013

it all depends on the system you have , if its TT then !00 Amp !00 MA Time Delayed RCD upfront with its usual earth stake , then 30ma RCD protection to outgoing circuits in the house , The supply to garage is only protected by the time delayed RCD and fused at this end , the other end a 30 ma rcd is reqwuired with another earth stake

Engineer54 · Feb 20, 2013

Ray Galea said:
it all depends on the system you have , if its TT then !00 Amp !00 MA Time Delayed RCD upfront with its usual earth stake , then 30ma RCD protection to outgoing circuits in the house , The supply to garage is only protected by the time delayed RCD and fused at this end , the other end a 30 ma rcd is reqwuired with another earth stake

If you look at the OP pic's, you'll see it's a PME supply!! lol!!

Mfctitch · Feb 20, 2013

thomas-1981 said:
Is this the fcu in the garage? And what cable are you suggesting it's protecting?

Yes fcu is in the garage and I'm hoping to protect the in coming cable as at the consumer end its being protected by a 32amp MCb

Mfctitch · Feb 20, 2013

Engineer54 said:
That cabinet around the CU can be easily replaced for a larger one. To be honest, it should be anyway there isn't any room for air circulation in that tiny cabinet!! So the earth system is a PME, at least now that can be taken into consideration... Going by what you have told us above i think your customs really asking too much from this 2.5mm supply to the garage etc.

Without going too much into detail, this now all depends on if the customer is prepared to pay for what he wants, if he's not then it's a pointless exercise for both you and us to prolificate on the details of what is needed.

Edited.... lol!!

Thanks again for your input

My hands are tied he does not want to pay for any changes in the house.

So as there does not seem to be away to add an extra RCD in the garage. It might be a case of leaving the whole house and garage protected by the main 63amp 30ma RCD and if something trips in the garden then the whole lot will trip.

Am I right so far?

Adding a 2 way unit to a garage

Mfctitch

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partypest

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Mfctitch

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eganelectrical

Engineer54

eganelectrical

Engineer54

Mfctitch

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thomas-1981

Engineer54

thomas-1981

Engineer54

R G

Engineer54

Mfctitch

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Mfctitch

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