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53 GONE AT LAST!
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Discussion Starter · #1 ·
Bit of a dilemma here, so bear with me if it gets a bit involved:whistling2:

I have to run a new sub main to pick up an existing distribution board. Load is 3 phase N & E 315A and cable is to be run internally beneath a raised floor [Comms Room].

Cable is to be installed on basket raised above the floor.

Best option is to use 185mm2 Single core AWA copper, one per phase and one neutral along with a separate earth[ sorry….CPC!] All calcs done and confirmed as suitable.

So, bonding of the armouring? Glanding is not going to be feasible as there is too little space; not needed for mechanical constraint as the cables can be anchored with cleats. Not going to move at 185mm2 anyway !!!.

Option # 1

Leave AWA long, insulate and ‘lug’ onto earth bar

Option #2

Insert aluminium sleeve between inner sheathing and AWA [ like cable joint to eliminate crushing inner sheath ] and compress with a jubilee type clip. Stainless steel is an option as the galv ones may cause electrolytic reaction. But, how to attach the ‘tail’ from here to the earth bar ? Copper direct onto Ali is going to be a no-no:no:

Anyone got any better ideas, comments, criticisms, or even done it before:(

All input gratefully appreciated

 

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Just a quick thought regarding the bonding,would Cu-Al bond be acceptable if steel was used.
I cant see any issues with the copper migrating any neutrons since this would have been done prior to manufacture at the copper mills,therefore steel maybe suitable to bond together the two metals???

Would it be possible to post photos of your completed install???,always open to new ideas!!!

Minky.
 

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53 GONE AT LAST!
Joined
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690 Posts
Discussion Starter · #3 ·
I think I have the solution...sort of!

I have managed to get [arrive tomorrow ] some Pirelli Shearnut cablejoints designed to mechanically join copper to ali on u/g joints. These have a plate which presses down onto the conductors by virtue of 2 shear nuts. So it is ali strands on one side and copper on the other. A copper tail will then be taken to the main earth bar. Gone for this option as crimping a lug onto the ali would be a compromise as we would have to guess the size of the lug required. :eek:

I will be interested to see how UU terminate the ali Earth on my incoming 400mm AWA service cables on the LV side of the 1000KVA transformer...may try to blag some stuff in exchange for cups of tea / coffee:whistling2:
I will report back
 
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