Crimps on Aluminium twin and earth cable.

Could galvanic corrosion between the aluminium and the crimp material be the cause of the failure? rather than overheating due to insufficient size. And would the materials used in wagos fare any better over time?

Edit; Seems the brass used in chockblocks might be a better choice

Colin Haggett: 
 

Looks like a bad repair from when it overheated at the fuse carrier. Probably best to rewire and lose all the aluminium cable and have a nice shiny new consumer unit. 

Am I right is assuming that the red shield is the type that only accepts Wylex cartridge fuse carriers and Wylex M.C.B.s? If so, the terminal must have been the cause, either a loose screw or deformed loose aluminium.

Z.

Zoomup: 
 

Colin Haggett: 
 

Also blue inline crimps are only rated at 15 amps

That's all right then innit? 15 Amps per leg if it is a ring circuit protected by a 30/32 Amp device.

 

Z.

Takes a lot planning to get a perfectly balanced ring to protect those crimps.

Zoomup: 
 

Colin Haggett: 
 

Looks like a bad repair from when it overheated at the fuse carrier. Probably best to rewire and lose all the aluminium cable and have a nice shiny new consumer unit. 

Am I right is assuming that the red shield is the type that only accepts Wylex cartridge fuse carriers and Wylex M.C.B.s? If so, the terminal must have been the cause, either a loose screw or deformed loose aluminium.

Z.

The first fault was the loose connection unfortunately badly repaired coursing a second failure to happen. 

As we can apparently edit posts indefinitely I have changed the topic title to say aluminium twin and earth as it may act as a warning to anyone considering using crimps on aluminium twin and earth cable. 

I definitely don't think it's a good idea. 

Sparkingchip: 
 

As we can apparently edit posts indefinitely I have changed the topic title to say aluminium twin and earth as it may act as a warning to anyone considering using crimps on aluminium twin and earth cable. 

I definitely don't think it's a good idea. 

Agreed.

Z.

A proper crimp would have a copper half and an aluminium half with the joint covered.  The Al end would likely be filled with special paste to aid crimping and electrical contact and to keep water out.  The aluminium end would be heat treated to match the condition of the aluminium cable and ditto the copper.  I have never seen them other than for use on overhead lines where they can provide a high quality joint if used with the right dies and tools.  The big issues with a straight copper crimp will be the differential compression of the core and crimp and different thermal expansion.  On expansion as Al expands about 30% more than copper for the same temp rise so the joint will soon be subject to some massive stresses which will quickly loosen the copper - al crimp. The actual crimping process will be a bit indeterminate too as Aluminium has a lower modulus of elasticity than copper so initially the core will compress relatively more than the crimp when the slack is taken up.  After that the copper will probably yield before the aluminium which may never permanently deform and that could mean that the whole permanent compression ends up in the copper.  Either way these crimps are not designed for dissimilar metals and will fail if moved or thermally cycled.

And the aluminium conductors are bigger to start off with.

Wago have increased the capacity of the 221 connectors, if you have a new box of Wago 221 Series they now connect conductor cross sections from 0.5 to 6 mm2 (20–10 AWG).

So they should adjust to suit the odd sized conductors and accommodate a bit of expansion and contraction, also they are plated, so are probably as good as it gets. 

I went to find the customer who was sitting in his garden and he said he thought I had gone home, I replied that I had been writing a short essay in the comments box on his electrical certificates, then sat and had a conversation.

Could galvanic corrosion between the aluminium and the crimp material be the cause of the failure? 

My understanding was that the problem with Aluminium is less galvanic or bi-metal corrosion so much as the Aluminium itself tarnishing in air - the tarnish is very much less conductive than the raw metal. As mentioned a paste is often used when jointing aluminium - but it's main role is to keep air out of the joint to prevent the aluminium tarnishing.

   - Andy.