Copper tails for aluminium sub mains

[ShaneR]

Hi all

What are the rules around copper tails, length and size reduction for joining to aluminum?

I'm going to run some 95mm Aluminium 390m underground.

I would like to add tails 5 - 10 meters on each end.

Never put tails on before.

[PeteRig]

You can use shearhead bi-metal connector links from Electrical Connections, I use the ECZS type which has double shear bolts at each end of the connector.
The tails I use are copper flexibles, generally you can go down one size (or more) for the copper cables eg 70mm Cu (depends on current/load etc)
So for your example I would use a part number ECZS1695, that gives cable sizes from 16mm to 95mm.
You can also purchase copper gauze ( for the copper cables if flexible) which helps with the connection in the connector link.
I use these connectors all the time and find they are easy to use, need to use also heavy duty Rachem to go over the links.
Still have to have cable protection etc
Cheers Peter

[gregmcc]

I've use both shear off and crimp links for this type of work, crimp links are cheaper, but lab our wise are more expensive. Shear offs although more expensive are a quick, easy and fool proof way, even easier if you have a rattle gun.

If the copper tails are the flexible type then use the gauze strips as it stops the copper splaying out like a bad haircut. Use heavy wall heat shrink to maintain the same or better insulation thickness, if your are burring the joint you will need 2 layers of heat shrink to maintain the double insulation.

We do heaps of transition joints cu-al and we almost always use shear offs.

Oh, and don't forget the jointing compound.

[ShaneR]

The tails I use are copper flexibles

Can you get flexables rated for buried direct?

[DougP]

Why are you planning on using such long tails?
And from your last comment, are you planning on doing the join underground?

Using such long tails, you are going to complicate the voltage drop calculation.
Not having the joint accessible, could cause some confusion for others unless the cable run is detailed somewhere on site.
And considering you have never put on tails before, to then complicate things further by doing a bi-metal join underground, might not be the best option if you can avoid it.

[PeteRig]

Yes you can, Tri-Cab cables make a variety of cables in 1c and multicore, still need to follow AS/NZS 3000 guidelines.
One thing to watch is when terminating lugs/links that there is a technique to follow, don’t remove all the insulation for the lug in one go, otherwise the fine strands of conductor will spray out, bell mouth lugs help make this easier when terminating.
Tr-Cab also make AL flexibles, so no need to break down the cables into copper, they manufacturer bi-metal lugs so you can bolt direct onto the copper connections. For some reason standard lugs/shearlinks don’t fit the AL flexibles, the connector companies are aware of this and looking at it.
The lead times of the cables when ordering needs to be checked, as Tri-Cab cables are manufactured in Australia.
You can get fire rated flexibles if required when cabling Life Safety Services.
I have been using flexible’s since the early 90’s when I worked for a company in helping the Americans set up Clear Communications in the 3 main centers in NZ, haven’t looked back, now use them for everything from gens to UPS’s. Especially good when cabling hi-rise apartment blocks for the apartment submains etc.
The cost of the cables has come down also making them cost effective to install.