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Copper Vs Aluminium


the doctor

Question

Hello All,

 

I have been away for so long...i have been busy with bust computers, fitting solar panels, collapsed marriage and a bit of courting in no particular order!

 

Now we have a large pv job to look at that requires a 300mm sub main installing.  The boss has priced it at £15000 for the cable (swa).  To do it in equivalent amperage Aluminium singles in duct is less than £4000. 

 

So the question is, what is the catch and how come everyone does not do the big stuff in aluminium?

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12 answers to this question

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Al, is a BA****D to terminate.

 

You MUST do it correctly.

 

It is prone to premature deterioration if not installed TOTALLY correctly.

 

You need Densal paste, or Bicon X1.

 

These days "H&S" prefers Bicon.

 

Look at the electrochemical series and the relationship between Al & Cu there, and remember that Brass is Al & Zn.

 

Look into electrochemical corrosion.

 

Al, forms an oxide on it's surface almost instantaneously it is exposed to the air, and I don't mean when you strip off the insulation, I mean when it is manufactured.

Hence why it is welded with an inert gas shield, e.g. Argon.

This oxide Al2O3 is an insulator, so, it acts as an insulator between the cable core and the terminal it is entered into, so you need to be careful with conductivity values and the "balance" of these.

i.e. if you had a few % difference in copper cable & brass terminations, you might not be worried, but in Al, you need to think about it.

 

Now also you need to consider the increased size of the enclosures needed to manipulate and terminate the stuff.

 

Personally I HATE it with passion.

 

It does have it's place I suppose, but, the largest use it had was DNO & public lighting, suffice to say that these organisations are now regretting the choice, certainly round here, near the sea...

 

I can give you more, but try this for now.

 

For me Cu all the way.

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The bitterness of poor quality is remembered long after a low price is forgotten......

 

Copper is used for cables for a reason!!

 

john....

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I would agree, the problem I have found in the past ( not used it for years) is the suitable jointing and containment. It is not nowhere near as flexible as copper and a real pain to work with.

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I had to make a special set of "benders" for when we terminate 400mm AWA singles into panel boards...it is a Biatch of the first water to bend...and is as forgiving as a Mother-in-law for termination/wrangling

Who amongst us can never forget AlCuMICC cable?.......NOT ME!

As much use as a galvanised condom

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TBH Kerch, never come across the AlCuMICC, thank goodness.

However, I have come across a LOT of underground public lighting AWA that had gone across to private ownership, KME & I did OK out of sorting it out, however, I would have preferred not to have.

All down to inadequate installation techniques.

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Well,if you ever come across it...i have some terms for it in the barn somewhere.-All sheradised glands and wege fit pots as you could not screw pots onto it

Even got a couple of Mole grip crimper /inserters for it!...these still work on copper for crimping the pot over

Just saying

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Used it in the early 80's, hate the stuff, bigger and more awkward to used for a given current carrying capacity, horrible to terminate and once it is bent / manipulated it couple of times it tended to stress crack.

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It has its place I suppose ,  you state a substantial saving in costs , so as long as you know the drawbacks , why not ?

 

  Always at least a size bigger for a start  and big spreader boxes  and as Sidey says , Densal paste etc . 

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Not necessarily just one size bigger Deke, it has to be totally re-designed around the CCC VD etc. of the Al.

Plus, if there is FITS involved, then it must meet the design lifetime of the FITS requirements...

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FITS   ?     :C

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Feed In Tariff Scheme, or Feed In Tariff('s).

AKA, coming under the REAL installer scheme for Renewable Energy.

In that it must meet the design life of the requirements of these "schemes" to ensure that the install is eligible for the payback from the Government.

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