new CU and garage wiring questions

[sherlockholmes]

Hello,
I'm planning to get a new CU installed as my home currently has no RCD protection. It's a Wylex box where the old wire fuses have been replaced at some point with MCBs. I'm basically wondering how much additional work is likely to be required based on the following-

Firstly, inside the house the power circuits are all grey cable ring circuits with 4mm2 cores (red + black) of about dozen copper strands and solid earth, the sockets being surface mounted to the skirtings. Assuming it passes insulation/continuity tests etc, is that a case of recommended improvement that can wait until I redecorate each room, or something that an electrician would have to do as part of fitting a new CU?

Secondly, the ancient CU (also to be replaced) in the garage about twenty feet down the garden is fed by a ring circuit of solid core 2.5mm2 pvc cable, run in conduit under the paved path and patio. There's a lighting and power circuit in there, and the last owner used it as a workshop for many years running his power tools. Currently it comes off an MCB in the house, could it stay as is (assuming tests show the cable itself is sound) and go on an RCD protected circuit from the new house CU into a mini garage CU? Or would the electrician have to run an armoured cable in order to keep power in the garage? If so, are electricians typically willing to let the homeowner do the donkey work of laying the cable? Because that is going to be a quite extensive undertaking with all the paving.

Thank you for your time, any additional info that is required please ask.

 

[securespark]

Have you had any quotes so far?

 

[sherlockholmes]

Have you had any quotes so far?

Not yet, I've got someone coming round to do a report on all the house electrics next week for a hundred and i'll use that to get some quotes on the CU swaps.
Just wondering if I need to prepare to be given bad news on the points I've raised, i'm not anticipating any other potential problems except a lack of extra earth cable in the bathrooms.

 

[ericmark]

There are a hundred and one ways to up-grade and test the electrics and often there are ways around problems.

But to work out which is the best or cheapest way without being on site is rather pointless.

My house also has Wylex fuse boxes which were converted to MCB's and each box is feed from a 30ma RCD so still in the main complies with new regulations. The only non compliance bit is the wood base to the CU.

So does need on site visit.

 

[sherlockholmes]

There are a hundred and one ways to up-grade and test the electrics and often there are ways around problems.

But to work out which is the best or cheapest way without being on site is rather pointless.

My house also has Wylex fuse boxes which were converted to MCB's and each box is feed from a 30ma RCD so still in the main complies with new regulations. The only non compliance bit is the wood base to the CU.

So does need on site visit.

With respect I think my main questions could be answered as generalities - can a garage be run off a 32A ring to a slave CU from the main CU, using a ring of 2.5mm2 cable in conduit under paving, and is the old red and black 4.5mm2 multi-stranded cable still acceptable, or will an electrician upon seeing these things require rewiring of them?
These seem more like regulations questions than house specific questons to me.

 

[holmslaw]

..

 

[sherlockholmes]

Thanks, but i'll wait for someone a little less terse.

 

[holmslaw]

..

 

[sherlockholmes]

I'm waiting for a civil conversation with an electrician, and I won't be holding my breath.

 

[holmslaw]

..

 

[ricicle]

I'm waiting for a civil conversation with an electrician, and I won't be holding my breath.

T0$$3r

 

[ban-all-sheds]

With respect I think my main questions could be answered as generalities

With respect you've come here for advice because you value the opinions of people who know more than you so don't start arguing with them when the advice you get is not what you want to hear.

can a garage be run off a 32A ring to a slave CU from the main CU,

Yes, but it would be utterly pointless to have a CU in the garage when the supply to it is limited to 13A.

using a ring of 2.5mm2 cable in conduit under paving,

No.

and is the old red and black 4.5mm2 multi-stranded cable still acceptable,

No such thing.

or will an electrician upon seeing these things require rewiring of them?

Yes.

These seem more like regulations questions than house specific questons to me.

And the reason you think you don't have to comply with the regulations is what, exactly?

 

[radweld]

These seem more like regulations questions than house specific questons to me.

And the reason you think you don't have to comply with the regulations is what, exactly?

I took this to mean the OP thought a general response their questions could be provided with reference to the regulations, as opposed to requiring a site visit as suggested by ericmark.

Indeed ban and holmshaw have actually provided some responses to the questions without (presumably) a site visit, which kind of proves the point.

 

[ban-all-sheds]

Hello,
I'm planning to get a new CU installed as my home currently has no RCD protection. It's a Wylex box where the old wire fuses have been replaced at some point with MCBs. I'm basically wondering how much additional work is likely to be required based on the following-

Firstly, inside the house the power circuits are all grey cable ring circuits with 4mm2 cores (red + black) of about dozen copper strands and solid earth, the sockets being surface mounted to the skirtings. Assuming it passes insulation/continuity tests etc, is that a case of recommended improvement that can wait until I redecorate each room, or something that an electrician would have to do as part of fitting a new CU?

Is what a case of recommended improvement?

What would you be changing when you redecorate each room?

Currently it comes off an MCB in the house, could it stay as is (assuming tests show the cable itself is sound)

No.

and go on an RCD protected circuit from the new house CU into a mini garage CU?

Yes.

Or would the electrician have to run an armoured cable in order to keep power in the garage?

Yes.

If so, are electricians typically willing to let the homeowner do the donkey work of laying the cable?

Yes.

 

[sherlockholmes]

With respect I think my main questions could be answered as generalities

With respect you've come here for advice because you value the opinions of people who know more than you so don't start arguing with them when the advice you get is not what you want to hear.

I have argued with no one, despite being insulted. I have no objection to being told that rewiring is required, but I do object to a terse one word statement rather than any attempt at any explanation. I do not particularly want to play twenty questions here.

can a garage be run off a 32A ring to a slave CU from the main CU,

Yes, but it would be utterly pointless to have a CU in the garage when the supply to it is limited to 13A.

Why would it be limited to 13A? As I have already mentioned, there is a ring circuit, from a 30A MCB in the house CU. This feeds a CU in the garage, which has a lighting and a power MCB adding up to less than the 30A supply fuse. Two cables from an MCB in one box are the supply for the second box. I am asking if this setup is allowable, obviously the 30MCB would be replaced with the CU replacement, presumably with an RCBO.

using a ring of 2.5mm2 cable in conduit under paving,

No.

My objection here is not that I dislike the answer, but that I would like a little more more information than 'no'. The ring setup is amply protected mechanically by being under paving, and the total current requirements of the garage to not exceed the current carrying capacity of the two cables. On what grounds are you stating 'no'?

and is the old red and black 4.5mm2 multi-stranded cable still acceptable,

No such thing.

I corrected the initial post to 4mm2 long before you replied, and even if I had not surely it's simple enough to state whether or no multi-stranded cable in good condition is recommended for replacement or not.

or will an electrician upon seeing these things require rewiring of them?

Yes.

Perhaps you could give a more considered response if you respond to the above.

These seem more like regulations questions than house specific questons to me.

And the reason you think you don't have to comply with the regulations is what, exactly?

I have no idea where you are coming from there. I did not suggest at any point that I do not need to comply with the regulations, and am clearly endeavouring to find out what the regulations say with regards to my questions.