Steel wired armoured cable as earth

Quick question. Can anyone confirm if the steel wire on a 4 core armoured cable can be used as an earth?

I’m doing an install for a friend and inverter is going to be in the garage so I need 4 cores for the power to the inverter and power back to house for a essential loads db. When I bought material, I got a separate earth that I was going to lay in conduit but today while laying the cable, I was wondering if the steel wire could be used for the earth. It’s a 27m run. I checked the resistance with my standard fluke and it showed 0.4 ohm. The 6mm earth cable I bought also reads the same.

Technically I think it’s fine but not sure from a regulations point of view.

Anyone know?

I can’t give a definitive answer from personal knowledge (domestic wiring is not my game). However, I can relay a recent conversation I had with a colleague who does COC’s in ZA.

It goes something like this:
The electrical tests have to pass, no wriggle room.

Apparently, new regs state that earth has to be done via a separate core, it is no longer permitted (only?) to use the cable armouring.

Because it once was permitted to use the cable shielding. Coupled with the practical difficulties associated with retro-fitting separate earth cores to legacy installations.
This now falls within the discretion of the person issuing the COC and it is unlikely that it will prevent the sign-off.

Thanks Phil

I already bought a separate earth so I might as well just use it then. Rather be safe than having to pull one at a later stage because someone has an issue.

SWA cables are great and should be used more often instead of surfix/twin & earth.
The issue with using the armour as an earth is that it requires that a few strands of the armour need to be fed through the CCG gland and these need to be terminated.
The glands often come adrift from the armour when under strain.
As far as the legalities are concerned I’m not sure. My house has an earth spike at the old meter box but it’s now disconnected… Is this where the earth should be terminated? I don’t see the utility providing an earth…

Have almost never seen in on industrial level thats not saying its not allowed just rarely see it myself. As said above when you terminate it with a gland you cut off a considerable amount.

I guess it depends on the type of earth system that you have. In your case, if the utility is not providing it and your spike is disconnected, then what’s your earth currently connected to.

In my case the utility provides the earth as well so I just bond everything to that, except my panels, which goes to a spike.

Regarding the SWA as earth, what you say does make sense about the gland holding the wires firm. It’s not so easy to ensure that it doesn’t come loose and one needs to ensure that the whole lot is clamped securely on both sides otherwise the risk of a inferior join increases.

As mentioned, will just run a separate earth. Will already have a conduit for the ct cable so it’s not much more effort.

As you said you have the wire why not use it. Or get 5 core SWA

South Africa mostly uses the TN-CS earthing system.
In this system, the Neutral is earthed at the substation and brought to your house as a single PEN (Protective Earth Neutral) instead of as two separate wires. Then where the supply enters your home, or possibly in your main DB, the PEN is split into separate N and PE wires.

Edit: Found a picture for clarity.

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According to Continental cables, the 5 core SWA is not available in SA, there is 7 core available in 1.5, 2,5 and 4 mm only…

Bigger sizes is only available in up 2, 3 and 4 Core.

Maybe some other suppliers sell them…

So one doesn’t need an earth spike in the ground on your premises?

No, as far as I know, it isn’t required in normal installations if you are on the TN-C-S system although it is a good idea.

I would have liked to just get 5 core but for some reason, the electrical shops Around me only keep up to 4 core.

Searched a bit online as well and it’s not very common. Oh well, ram the separate earth yesterday so it’s done now

I’m sure I have seen somewhere that you shouldn’t use a separate earth spike with a TN-CS system except for solar panels and this should anyway be isolated from the municipal earth.

This makes sense from an earth loops perspective