Crimping - Old Alu Wire to New Copper?

[shocksmith222]

Hi All,
I am in the middle of a rewire and install of new CU with RCD's. So far all lighting circuits have been rewired with new copper but customer has advised me that their budget has dried up due to a redundancy. They have asked if I can finish up the install of the CU by simply extending the sockets, existing wiring to the new CU with new copper wire, so that the sockets are RCD protected.

I just thought I would post the question raised to me by the customer about whether or not the existing Sockets (Ring Circuits) which are wired with 2.5mm Aluminium (T&E) can be extended/crimped to short lengths of 2.5mm copper (T&E) and terminated at the new CU?

Obviously, the current carrying capacity of each is different so I have initially advised that this is a NO from my point of view. However, I would be interested to see what other sparks would do or advise in a similar situation. I do feel sorry for the customer as any job loss is really distressing but I am not prepared to go against regs or safety because of cost. I do want to do the right thing for the customer and if possible keep the cost down.

Thanks in advance.
S.

 

[Spudnik]

Providing the old circuits test through ok, then there is no reason why you cant extend them.

No different from a normal CU change.

Just make sure you note it on the cert everything you have done.

 

[acat]

Dont know if this puts a spanner in the works 522.5.2 Dissimilar metals liable to initiate electrolytic action shall not be placed in contact with each other, unless special arrangements are made to avoid the consequences of such contact.


Chris

 

[mogga]

2.5 alu twne?? would this pass on current carrying capacity??

 

[Deleted member 9648]

Ali was widely used during a period I think in the early 70's when there was an acute copper shortage.The 2.5mm equivilent was larger to allow for the reduced current capacity.
Dont crimp it....there is an estate in my area with a lot of ali and I've come across several CU changes with crimped joints that have cooked.I concluded it is because the soft ali continues to compress after the crimp is made and works loose.
I use a standard 30a connector with the two conductors laid parallel,the screw nearest the insulation I tighten just enough to secure both conductors...(if you overtighten there is a risk of almost severing the ali conductor).the second screw is wound up good and tight. I've never had one done like that fail.

 

[Bromd123]

I agree with ACAT if alu and copper come into contact they cause corrosion dont they?

 

[benji]

you could use anti-oxidation paste,when you do a large thro.joint you have the option of thro.crimps or mechanical connectors with shearbolts the mech.connectors are aluminium .only problem with small alu.cores and crimping is the crimp can damage the core.

yours benji

 

[Deleted member 9648]

It seems an electrolyte must be present for corrosion to take place,in dry conditions this is unlikely....which has been my experience in normal inside domestic situations.
Corrosion

 

[Risteard]

I agree with ACAT if alu and copper come into contact they cause corrosion dont they?

I've always tried to avoid connecting different metals for that reason. I certainly wouldn't do it without confirming first that they won't react.

 

[ian.settle1]

Hi All,
I am in the middle of a rewire and install of new CU with RCD's. So far all lighting circuits have been rewired with new copper but customer has advised me that their budget has dried up due to a redundancy. They have asked if I can finish up the install of the CU by simply extending the sockets, existing wiring to the new CU with new copper wire, so that the sockets are RCD protected.

I just thought I would post the question raised to me by the customer about whether or not the existing Sockets (Ring Circuits) which are wired with 2.5mm Aluminium (T&E) can be extended/crimped to short lengths of 2.5mm copper (T&E) and terminated at the new CU?

Obviously, the current carrying capacity of each is different so I have initially advised that this is a NO from my point of view. However, I would be interested to see what other sparks would do or advise in a similar situation. I do feel sorry for the customer as any job loss is really distressing but I am not prepared to go against regs or safety because of cost. I do want to do the right thing for the customer and if possible keep the cost down.

Thanks in advance.
S.

You should rip all the aluminium cable out as the minimum size you can use for aluminium cable is 16mm also as said unless you use joiting paste between the disimilar metals you will get electrolytic reaction and they will corrode away thus causing a high resistance joint.

Are you sure it is aluminum cable and not old tinned imperial stranded cable?

 

[shocksmith222]

Well first of all, a BIG thanks to you all for your replies to date, greatly appreciated.

I really don't know what to do for the best...but crimping is off the list, remaining options are:

1. Connect via standard 30a connector (with each wire in parallel)
2. Rip & Replace all the old wire (but customer doesn't want me to do this due to added costs!)
3. Establish if the old wire is Aluminium or as one suggested may be imperial tinned twisted wire (I have to be honest and say I have not seen this type of wire so I dont know what it would look like).

Well, I am going to have to make a decision as the job needs to get on or stop.

Thanks again for all the replies.

S

 

[rocker]

I may be wrong but I'd say if it's tinned copper, if you chop into it you will see a copper colour inside the strands.

What about helacon/wagos? Or a din rail style connection enclosure.

 

[Deleted member 9648]

You should rip all the aluminium cable out as the minimum size you can use for aluminium cable is 16mm also as said unless you use joiting paste between the disimilar metals you will get electrolytic reaction and they will corrode away thus causing a high resistance joint.

Are you sure it is aluminum cable and not old tinned imperial stranded cable?

In an ideal world yes,but you cant force the customer to cough up for that and if there are no other issues as far as I can see leave it alone.
I've seen plenty of copper to ali joints which have been made with care and are showing no signs of corrosion after many years.....in a dry stable environment you wont have any problems.

 

[shocksmith222]

Have been continuing my web investigations and it looks like it may be a possibility (seeing as the house was built in the early 1950's) that the sockets wiring could be Imperial Tinned Copper T&E, so I am going to have a closer look tomorrow.
The wire was red/black strands in what looks just like standard modern PVC sheath and with an extra bare (earth) included.

Thanks again for all you guys support. I will of course (for those interested) post what the outcome eventually is.

Ta
S

 

[Deleted member 9648]

Ali is a lot softer,bendy-er and lighter feeling than tinned copper....you will be able to tell from the feel of it.