Copper and Alluminium wires

garymcgee · Nov 21, 2009

Hi everyone,

Just joined this morning and thought I'd introduce myself.

I'm Gary Mcgee and am An Electrician from Glasgow and I have a question for you guys (or girls) out there.

I'm on a particular job at present, a very old, large, sandstone building that is having some alterations done. I'm running a few new circuits ie 2 x ring circuits and a few lighting circuits, not heavily loaded at all, however my problem is that the electrical distribution boards are of the old 20a re-wireable fuse carrier type by MEM and obviously I require a small consumer unit with rcd protection.

Looking around the main switchroom there's no possible point left that I could take a fresh armour from to supply the consumer unit that I require.

I intended to join into the live and neutral wires supplying the old DB (using proper blocks) with suitable tail of my own to supply my small consumer unit. The cables supplying the old db by they was are protected by a 100a isolator mounted just beside the DB so are protected.

My concern is this the single core cables (L & N) that supply the old DB from the 100a isolator are i am sure of Aluminium and I would be using copper double insulated cables to tap off from these.

Can anyone confirm if this would be satisfactory or not?

Sorry for the story.

Thanks
Gary

Dan · Nov 21, 2009

Welcome to Electricians Forum | Electrical Advice Forum | An electrical forum for electricians in the UK!

Hello garymcgee, welcome aboard www.electriciansforums.net. Stick around, I'm sure you'll like the place.

Darkwood · Nov 21, 2009

Isnt their a busbar chamber feeding these existing old points, can you use the isolator to feed your new board then feed the existing board from your new board this is one solution but it wont give disrimination with downstream devices. Can you get some pics on as their maybe a solution you missed.
Welcome by the way.

garymcgee · Nov 21, 2009

Thanks for the Reply

There is no main Busbar chamber as this is what I hoping I would find. The set up is like this, From the main service intake - to a main Isolator for everything and then into a main 3 phase service distribution panel that has no spare fuses in it. numerous isolators are then supplied from the distribution panel and in turn each DB around the building.

Another way out would be to change the existing DB with a new consumer unit i suppose, the only downside being that it is all single cores in the DB and would take time to trace the Neutrals, there's not to many circuits in it though. ( Single phase ).

Gary

Mr Mark Sparks · Nov 21, 2009

gary you can join copper to aluminium but you have to apply a paste to stop the two reacting
i will see if i can find it online

Guest123 · Nov 21, 2009

Welcome along.

patricklondon · Nov 21, 2009

hello gary theres no regs ringing a bell about not being able to use ali. i'm sure that if all the readings are ok then its fine. welcome to the forum.

i hadn't heard of marks special paste until now but i bet there is plenty of it online!!!

garymcgee · Nov 21, 2009

Thanks for the replies

I'll need to decide, paste or board change giving me spare ways anyway.

Obviously I need RCD protection for my new circuits (t&E), if I do the board change and reconnect into the new board the 4 or so old circuits that I need to keep it should be fine not to give these circuits RCD protection due to the fact that they are in metal conduit, is that correct?

Say these old circuits were T&E, would a board change mean that you have to include these on an RCD, i mean an older property is not up to the 17th spec for a start and adding an RCD could throw up problems that had no adverse consequence before the board change was introduced.

Thanks again

Gary

Mr Mark Sparks · Nov 21, 2009

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this is it

garymcgee · Nov 21, 2009

Thanks for the info Mark

I see that they have a place down South, will give them a call.

What do you think regards my last post regards the RCD situation?

Cheers

Gary

electricAl · Nov 21, 2009

Unfortunately Gary (& welcome aboard BTW) whilst it sounds perfectly plausible & reasonable to make alllowances for old properties, we`re not permitted to apply The Regs discriminatedly. All new installations do need to have the same safety margins built in & no compromises are really applicable as such.

As to the question of RCD protection, it really does depend on a number of variables. All S/O ccts for example, require 30mA RCDs, as do all ccts supplying a bathroom.
What exactly do these old ccts feed?

garymcgee · Nov 22, 2009

Sorry for the delay in replying

I know what you mean regards applying the regulations, however I do get the feeling that the regulations in general can be interpreted differently by everyone, you wonder why they can't make it an easy book to read and understand easily.

With regards to the situation that I am talking about I do know that there are probably two radial circuits for sockets and i'm certain that a bathroom is on a lighting circuit, I'll take a closer look on Monday.

Getting back to the need to give the old circuits RCD protection or not, I know the regulations does state that although older installations will not meet all the current requirements of the new regs it does not mean that these installations are dangerous, I was not sure changing the DB with a newer consumer unit to include the new circuits would then mean that the older circuits would have given addition protection to what they had in the past.

Take changing a consumer unit in an older house, the regulation state that circuits are required to be arranged for example to avoid an RCD nocking out all the lights in a house. Whilst all testing might be ok, to sort that issue out you would need to rewire circuits. How far do you go?

Anyway, I 'll let you know of these circuits.

Thanks
Gary