what is the minimum cable you can use for a100A single phase ccu

chris- · Jun 25, 2012

hello sparks,
what is the minimum cable you can use for a100A single phase ccu, the meter is out the front of the house and the ccu is 10m inside the house cable must come in under house duct? please solve this argument im having.

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and should it be armered

chris- said:
hello sparks,
what is the minimum cable you can use for a100A single phase ccu, the meter is out the front of the house and the ccu is 10m inside the house cable must come in under house duct? please solve this argument im having.

topquark · Jun 25, 2012

I take it you're just asking about the L&N in which case 25mm double insulated is the stated reqt. Although for that distance it should really have a switch fuse as the DNO only usually "prefer" it for a max of 3M. So down to you to decide based on type of cable/environment. You could decide that 2 core 16mm SWA (and separate, appropriate sized main earth) was suitable.

Rockingit · Jun 25, 2012

Well.....a few bits to this!

Firstly, any 'tails extension' needs to have additional fused protection/isolation, so you'll need to fit a suitably rated CPD immediately after the meter (in your case).

Second, whilst there's no specific requirement to use one form of double insulated cable over another, you'll probably find that SWA or tuf-flex type works out cheaper than singles. If it's armoured then you need to make sure it's properly glanded and banjo'd, and the armour is highly unlikely to be sufficient to carry your TN earthing, so it'll need to be 3 core or run a separate earth (3 core normally cheaper!).

Thirdly, whether the cable needs to be 25mm or 16mm (or maybe even 35mm) all depends on your calculations and looking at the tables in the BGB appendixes and considering the installation methods and de-rate factors as applicable.