Adding a 2 way unit to a garage

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Adding a 2 way unit to a garage

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Mfctitch

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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
 
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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.
 
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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.
Click to expand...

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.
 
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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
 
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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
Click to expand...


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!!
 
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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??
Click to expand...

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??
 
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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.
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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!!
 
Last edited by a moderator:
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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!!
 
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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
 
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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
Click to expand...

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

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?
 
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Mfctitch said:
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?
Click to expand...

He can't have what he is not prepared to pay for, so leave the system as it is and let the lot trip out!!

One thing, have you opened the house CU, i am just wondering if this may be a split CU where only some of the circuits are RCD protected?? You may have mentioned before, but can't be arsed to read back through so many posts !! lol!!
 
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You've lost the plot what about me :)

So what would you like to know?

And to answer Thomas-1981

My reasoning with the 2 way DB was that if I leave the fsu in place and come off of that with the 2 way DB I could at least tidy the circuits up and give the customer the sockets that he wants on the understanding that if he overloads the circuit then the 13 Amp fuse might go before the MCB trips.

I'm not saying this is right but my options are very limited and to be honest as long as its safe I would rather not lose the job. because he will just get someone else in who might well just fit the sockets and run.

Opinions as always very welcome

Ps I take it that no one has come up with a way of supplying an RCD just for the garage bearing in mind that the whole board is protected by and RCD.
 
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Mfctitch said:
You've lost the plot what about me :)

So what would you like to know?

And to answer Thomas-1981

My reasoning with the 2 way DB was that if I leave the fsu in place and come off of that with the 2 way DB I could at least tidy the circuits up and give the customer the sockets that he wants on the understanding that if he overloads the circuit then the 13 Amp fuse might go before the MCB trips.

I'm not saying this is right but my options are very limited and to be honest as long as its safe I would rather not lose the job. because he will just get someone else in who might well just fit the sockets and run.

Opinions as always very welcome

Ps I take it that no one has come up with a way of supplying an RCD just for the garage bearing in mind that the whole board is protected by and RCD.
Click to expand...

Seemingly no without extra costs so quote to leave as is and make sure that your quote points out the "issue" so they will only have themselves to blame for when tripping starts later on.
 
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Read through this lot and come to the resounding conclusion.... it looks like the only solution is a short walk back to the main CU to reset RCD.

First world problems or what man....
 
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wade88 said:
Read through this lot and come to the resounding conclusion.... it looks like the only solution is a short walk back to the main CU to reset RCD.

First world problems or what man....
Click to expand...

That's if you even have any rcd tripping issues

If its not tripping now then I can't see it being much different with a 2way cu in the garage lol

No different than the existing setup !
 
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The initial question on page 1

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.

Now 9 pages later.is that 15 per page?
If so we are up to 135 ish posts and it culminates in the following question
Ps I take it that no one has come up with a way of supplying an RCD just for the garage bearing in mind that the whole board is protected by and RCD.

It's kinda self satisfying to know that this forum sure doesn't lack perseverance
As for losing the plot,was there ever a plot to lose lol


Oh and by the way,it seems I have stuck with it till the end
icon11.png




 
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Des 56 said:




The initial question on page 1

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.

Now 9 pages later.is that 15 per page?
If so we are up to 135 ish posts and it culminates in the following question
Ps I take it that no one has come up with a way of supplying an RCD just for the garage bearing in mind that the whole board is protected by and RCD.

It's kinda self satisfying to know that this forum sure doesn't lack perseverance
As for losing the plot,was there ever a plot to lose lol


Oh and by the way,it seems I have stuck with it till the end
icon11.png




Click to expand...

Morning Des 56

Yes you and a few others have been very helpful and very persistent.

It does look however that the best I can do for this customer is advise him of the pit falls as has been suggested.
Cost the job with a 2 way board and fit the sockets and lights as he wants.
It is a shame that I can't find a way to fit an RCD for the garage sockets but as has been mentioned if he does not want the cost or the disruption then there is very little I can do.
 
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