SWA Earth

[wreck-it-steve]

Hi,

When earthing the armour in SWA what size should it be? do you earth it with 4mm cable?

Thanks

 

[holmslaw]

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[wreck-it-steve]

It should be at least half the size of the main conductors and a minimum of 2.5mm cu if mechanically protected, and 4mm cu if not mechanically protected.

There is nothing bigger than 6mm SWA on my property but the last owbers did not earth the armour at either end... to save me buying differnt size earth cables can I do them all in 4mm? do you earth one end or both?

 

[holmslaw]

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[scottyboyiow]

What earthing arrangement do you have Stevo66 and what is the SWA feeding?

 

[ericmark]

If the SWA is really only for mechanical protection and there is one of the cores used for the earth to what it is feeding then yes 4mm is ample.

If however you are using the SWA to transmit the earth connection one then needs to look at cable size as well.

Although we should use brass bolts and banjo rings to connect the earth where one of the cores are also used I do not really worry and have used roofing bolts in the past. And really only a need to connect up the supply side of the cable to earth.

However using both the SWA and a core for earth will clearly reduce the earth loop impedance and if I was relying on this reduction to comply with the regulations I would always use brass and copper for all electrical connections.

You have not said what it's feeding, what size the cable is, or what the earthing system is, or what is the earth loop impedance.

It is possible that the cable feeds a shed which is TT from a house which is TN in which case one would need some careful consideration before changing the earthing arrangements.

I remember when working at Sizewell Power Station being sent to the caravan site to connect earth cables from the small shed by every caravan to the caravan chassis without being given assess to the caravans. In hind sight this was a dangerous move as it was latter found many of the caravans had ELCB-v fitted and my actions had resulted in these no longer functioning. I had to return and fit RCD's in all of the small sheds just in case the caravan had the old ELCB-v rather than ELCB-c (RCD) fitted.

With this in mind I would ask for further information before saying what cause of action to take as it could may things worse not better.

 

[wreck-it-steve]

The SWA is only for the cable protection and there is one core in all of them that provide the earth. They supply feeds to pumps and fridge controls, one is also a sub main to a small shead.

 

[holmslaw]

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[wreck-it-steve]

The SWA is only for the cable protection and there is one core in all of them that provide the earth.

The SWA still has to be earthed.

Yes I know... I was just telling you all what the SWA did etc so you could tell me if 4mm will be OK just to protect the armour.

 

[holmslaw]

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[ban-all-sheds]

Yes I know... I was just telling you all what the SWA did etc so you could tell me if 4mm will be OK just to protect the armour.

Against what?

 

[Lbourgh]

Bonjour
This may have be mentioned before n I'm sorry if it has .. Ive got a 1.5 3 core swa supplying several out door lights the swa terminates inside a plastic wiska box with plastic glands one in n one out and does this for all the other wiska boxes and I was wondering could I just change one gland to metal and earth that side and then tierap the earth to the next leg of the armoured again with one gland metal on the next wiska box So on each box will have one metal gland and one plastic To save time

Thanks