Dedicated Radial Plan

Yes i figured the SY cable braiding could terminate with a gland but without holding the cable to anything, the banjo washer (or perhaps better an earth-nut) could then be fitted as so to connect to an earth strap - a suitable length and gauge of green/yellow earth wire that goes within the CU to fix to the earth bar.

In other words the SY braiding part of the cable would terminate within the cavity wall located close behind the CU, and only the L, N, E wires, and plus the additional earth wire would continue into the CU for connection.

As far as I’m aware the braid would connect to a banjo inside the CU so that it can be connected to earth within the box. Something like this, which shows SWA cable. I’m assuming you would do the same with SY.

no nothing like that, the fuse box is plastic so no earth there, also the cable is coming in from cavity wall behind the box, not the visible wall side, so this conventional way is unsuitable.

The cable would dangle down freely within the cavity wall behind the CU, although in all fairness all the other cables do exactly this anyway, and i would expect the main purpose of clamping the gland to the box side is merely for support in an area where it may be vulnerable to getting knocked about, whereas in a cavity wall it will be safe in that respect.

I checked CY and SY. They seem intended for situations where immunity from EMI is required or where data runs nearby. I couldn’t find reasons for which one to use other than that SY may be easier to bend. There is YY also.


I expect @Mike-B would know :slightly_smiling_face:

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There will be an earth in the CU so the Earth Conductors can be earthed.

This information may help;

Do consumer units have to be metal?

Since regulations changed in 2016, all domestic consumer units must be either enclosed in a non-combustible material or housed in a cabinet made from a non-combustible material.

These rules were put in place to contain any fires that broke out in the consumer unit within their casing, stopping the spread of flames. Consumer units made out of non-combustible metals such as steel would pass these regulations.

The rules only apply to consumer units positioned within domestic buildings, so anything installed outside wouldn’t be covered.

Do plastic consumer units have to be replaced?

Old style plastic consumer units no longer meet new regulations, however they don’t need to be replaced. So long as their safety features are up to date (such as old MCBs updated to RCBOs) and they are fully enclosed in a non-combustible casing, they can remain in the property.

Are plastic consumer units legal?

Yes. You can buy a brand new plastic consumer unit, so long as it’s housed in a non-combustible casing. Any old plastic consumer units are still legal too, they’ll just need new casing to make them meet regulations.

Consumer Unit Regulations Guide 2022

This generally means that all domestic installations must now have a metal consumer unit installed, unless the consumer unit is installed within a non-combustible enclosure.24 Dec 2021 › c…

If you need guidance, contact the;

  • Electrical Safety First

Hope this helps.


I don’t think it makes any difference whether your CU is plastic or metal, either way the cable braid connects to the CU earth block. A suitable gland would provide a simple way to do that. If you don’t need the gland for its other purposes such as providing a seal or strain relief, fair enough, but then you need to find another way to reliably connect the braid to earth. Either way I’m sure your electrician will be able to deal with it.

CY is copper (tin plated) & SY is steel.
Steel satisfies the robust industrial protective aspects of shielding, copper is electrically superior.
CY is the audiophile choice.

Remember the shield is a noise screen, it should not be part of the earth (E) (ground) circuit, it should act as a single ended grounded conduit
Connect the shield to the power end(s) only, leaving the end(s) towards the load not connected.


I presume you could just separate the braiding, then insert it into some earth sleeving, as you would a singer bare earth wire, then insert into the earth block in the plastic CU. May also be worth putting electrical tape around where the braising first protrudes from the insulation

Thanks Mike
A bit academic to me really, but i intend to use an earth strap from the CU to connect up with an earth-nut gland on the SY cable braid, the other end of the cable will also have a gland fitment into a small metal adaptor box, however this box will be isolated from any further earthing. The internal N, L, & E wires will connect up to double unswitched sockets as per usual.

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Hi Debs, Not yet persuaded by @Mike-B to use CY?


I’m not persuading anyone, just answering the question on the difference between CY & SY.
However, if I was selecting a cable for a fixed domestic installation I would go for CY, but its really is not that critical.

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I don’t need an audiophile choice, bunch of weirdos them folk, i’m merely a music lover so will be more than happy with steel :sunglasses:



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