Reterminating swa in cu.

[shaky1105]

My mate has an swa cable terminated in his CU incorrectly. It's either a 2.5mm² or 4mm² 3 core (I'm guessing judging by the size) but it's just been taken straight in via a big 32mm stuffing gland so the armouring isn't terminated at all. According to what he's told me, it looks like the only knockout left available was a 32mm one and the person that did it for him tried to drill it out as a 20mm but failed miserably (not surprising I suppose !).

Seeing as the CU is internal and doesn't really need a waterproof connection, would it be OK for me to reterminate it for him using a 32mm swa gland ? I know it's massively too big for that size of cable but I was just thinking then at least I could expose a bit more armouring to get in the gland correctly and earth it for him to make it a bit safer.

The cable feeds a small outside shed where he charges his e-bike and leaves a battery tender type charger on his motorbike if that makes any difference.

TIA

 

[Adam_151]

https://www.cef.co.uk/catalogue/products/23838

 

[shaky1105]

I didn't realise those even existed @Adam_151 thanks Just to confirm, looking at that reducer, I would just fix that to the CU internally with a 32mm Earthing Nut then simply screw the 20mm gland into it yes ?

 

[Adam_151]

Yes, personnaly I'd probably use a 32mm earthing nut on the inside, But nothing to stop you taking a banjo out the pack of a 32mm gland and using that and a 32mm locknut, or even just making sure you scrape the paint off inside the enclosure where the locknut tightens down on it. Sometimes you see a banjo between the gland and reducder with a flylead comming off it, and while tehcnically nothing wrong with it - It just looks a mess to my eyes

 

[JohnW2]

My mate has an swa cable terminated in his CU incorrectly. It's either a 2.5mm² or 4mm² 3 core (I'm guessing judging by the size) but it's just been taken straight in via a big 32mm stuffing gland so the armouring isn't terminated at all.

How is the other end of the SWA terminated - in particular, is the armour properly earthed there?

Is it a plastic or metal CU we're talking about?

Kind Regards, John

 

[bernardgreen]

One option for terminating SWA into a plastic CU is this

 

[ericmark]

SWA is often used outside, and outside is often outside the equal-potential zone, so step one is to work out if the armour should be earthed at one end or both? Personally I would bond to the supply end, but if the earth one end is TN-C-S and other end is TT then the armour will only be earthed at one end.

The cable feeds a small outside shed where he charges his e-bike and leaves a battery tender type charger on his motorbike if that makes any difference.

Yes it does, my e-bike has a class II supply so it does not use the earth, but an EV motorbike and an e-bike are not the same, most cars which are EV have the charger built into the car, and need a supply earthed with reference to the real earth outside. I say referenced as it may not be using TT but has some earth rod to tell it if the supply earth and local earth are within 70 volt of each other. Anything else is 50 volt, for some reason EV are permitted 70 volt. And because of the strict requirements, this requires special training, to do it safely.

In the main an EV runs on somewhere around 500 volt, and there is a very special device built into the EV to allow charging at varying rates.

However the e-bike uses a 36 volt or 48 volt battery, often the power supply is marked to show the output is isolated from the supply, and often in a plastic case, so all the special requirements for EV's in general are not really required for the e-bike.

Personally I charge the battery in the house, even if e-bike left in the boot of the car. I don't tend to use it from home, hills too steep even for an e-bike.

The problem is loss of PEN, click here to learn more and this is a problem with metal earthed items outside the earth zone, so charging in a garage no problem, with a shed or garage the material used is also important, tin sheds are different to wood sheds.

I am not saying the armour should not be earthed, what I am saying is it may not want to be earthed, and to dive in modifying can be dangerous, you need to take over the job, and step one is read the installation certificate for the job so you know what the intentions were. And of course you will need to issue a minor works or installation certificate after your changes.

 

[shaky1105]

Yes, personnaly I'd probably use a 32mm earthing nut on the inside, But nothing to stop you taking a banjo out the pack of a 32mm gland and using that and a 32mm locknut, or even just making sure you scrape the paint off inside the enclosure where the locknut tightens down on it. Sometimes you see a banjo between the gland and reducder with a flylead comming off it, and while tehcnically nothing wrong with it - It just looks a mess to my eyes

The suggestion for the 32mm earth nut was because of the limited space below the CU because of a cupboard. I also think they look a lot better than having a hole drilled through the unit and a separate banjo and nut.

How is the other end of the SWA terminated - in particular, is the armour properly earthed there?

Is it a plastic or metal CU we're talking about?

Kind Regards, John

The far end in the shed is terminated in a little plastic 2-way unit with a 16A MCB for the two sockets, a 6A MCB for the solitary light fitting and an RCD Main Switch. The crazy bit is that the SWA is terminated via a BW type gland but there isn't a banjo on it or an earthing nut so the armouring isn't earthed anywhere. It's about 6' from where the cable comes out of the wall of the house to the shed and the cable is clipped along the wall. I was thinking that maybe the installer had earthed the armouring at the far-end from the CPC conductor in the SWA but obviously not ! The overall install is quite neat actually but obviously wrong so maybe the person that did it was just having an off day ? who-knows. The main House CU is metal. I did think the easiest way would be to earth it in the shed unit but (and bare in mind here I'm a DIY'er, not an electrician) that didn't seem to be "right" to me so I looked at the main CU end and figured it would be better to sort it there seeing as there is enough cable/armouring to gland it.

One option for terminating SWA into a plastic CU is this

View attachment 354184

Not possible in this case as the cupboard below is only about 2" below the CU but thanks for the suggestion.

SWA is often used outside, and outside is often outside the equal-potential zone, so step one is to work out if the armour should be earthed at one end or both? Personally I would bond to the supply end, but if the earth one end is TN-C-S and other end is TT then the armour will only be earthed at one end.

Yes it does, my e-bike has a class II supply so it does not use the earth, but an EV motorbike and an e-bike are not the same, most cars which are EV have the charger built into the car, and need a supply earthed with reference to the real earth outside. I say referenced as it may not be using TT but has some earth rod to tell it if the supply earth and local earth are within 70 volt of each other. Anything else is 50 volt, for some reason EV are permitted 70 volt. And because of the strict requirements, this requires special training, to do it safely.

In the main an EV runs on somewhere around 500 volt, and there is a very special device built into the EV to allow charging at varying rates.

However the e-bike uses a 36 volt or 48 volt battery, often the power supply is marked View attachment 354191to show the output is isolated from the supply, and often in a plastic case, so all the special requirements for EV's in general are not really required for the e-bike.

Personally I charge the battery in the house, even if e-bike left in the boot of the car. I don't tend to use it from home, hills too steep even for an e-bike.

The problem is loss of PEN, click here to learn more and this is a problem with metal earthed items outside the earth zone, so charging in a garage no problem, with a shed or garage the material used is also important, tin sheds are different to wood sheds.

I am not saying the armour should not be earthed, what I am saying is it may not want to be earthed, and to dive in modifying can be dangerous, you need to take over the job, and step one is read the installation certificate for the job so you know what the intentions were. And of course you will need to issue a minor works or installation certificate after your changes.

Sorry if I inferred that it was an EV motorbike fella. It's actually a fairly old Honda CB750 that doesn't get a lot of use so he has an Optimate Tender Charger connected up to it permanently to avoid the alarm discharging the battery. He charges the battery in the shed coz one of his mates had an e_bike with a dodgy chinese copy charger that caused a fire so he wants to try to avoid that happening by charging it away (albeit only 6') from the house.

 

[Murdochcat]

There is nothing in the regs which says which end the SWA needs to be glanded properly. I always do it at the supply end but in this case the load would be OK

 

[SUNRAY]

There are many ways to adequately terminate the armour including:
CET glands

Terminating the wires direct

Bespoke enclosures

I'm not suggesting any of these methods for the current thread, just pointing out there are a number of alternatives to a brass gland.

 

[ericmark]

I know my Lidi 6/12 volt chargers are class II so it would not matter if not earthed, clearly should be an earth in case socket used for something else, however I would be wary about jumping in and saying what is there is wrong, as there may be an earth rod.

 

[JohnW2]

I know my Lidi 6/12 volt chargers are class II so it would not matter if not earthed, clearly should be an earth in case socket used for something else, however I would be wary about jumping in and saying what is there is wrong, as there may be an earth rod.

I don't think it has been suggested that the shed (hence sockets in the shed) do not have an earth - that is presumably provided by one of the cores of the 3-core SWA. The question and discussion are only about earthing of the armour of the SWA (in addition to it containing a CPC core)/

 

[ericmark]

I don't think it has been suggested that the shed (hence sockets in the shed) do not have an earth - that is presumably provided by one of the cores of the 3-core SWA. The question and discussion are only about earthing of the armour of the SWA (in addition to it containing a CPC core)/

I agree, my main concern is all too easy to criticise without knowing all the facts. Indoors easy, it is part of the equal potential zone, it would be rare to find otherwise, but out doors, the story is very different, and although lack of earth connection may be an error, it may also be by design. So I am wary of saying earth to this that or other without knowing whole story.

Where I live as you know, it is notifiable work, it was in England, but has since charged. Pictures are good, I am also considering a e-bike charging point, once I get new sheds, and I also use extension leads to charge my ICE car battery from time to time, as not used enough to keep battery charged.

I take a chance, I feel the likely hood of a loss of PEN is so remote not worth worrying about for the odd time I use a class I item in the garden, and even if lost, I do have an earth rod, so seems unlikely it will exceed 50 volts before I am alerted of the problem. But we at the moment have no idea of the supply, it may be TT for whole house, so no problem.

We know there is a RCD in the shed, and MCB's in the shed, so the work would have been notifiable, but we have not been shown the installation certificate.

 

[JohnW2]

I agree, my main concern is all too easy to criticise without knowing all the facts. Indoors easy, it is part of the equal potential zone, it would be rare to find otherwise, but out doors, the story is very different, and although lack of earth connection may be an error, it may also be by design. So I am wary of saying earth to this that or other without knowing whole story.

Fair enough - as you say, one can't confidently comment or advise without knowing the full facts - which is always an issue with a medium like this.

However, in reality, I think it's pretty unlikely that someone would use 3-coreSWA without one of the cores being used as a CPC, isn't it? In fact, that would not really be different from the very unlikley event that someone 'ignored' the CPC in any cable in an electrical installation.

 

[shaky1105]

Thanks for the replies guys. I'll have a look sometime over the weekend to see if I can see any evidence of an earth rod in the shed but tbh I think I might just try to persude him to get a sparkie in to have a proper look at it. If it'd just been a case of reterminating the cable to provide a proper connection for the armouring I could've done that no problem but now you've started talking about separate earthing arrangements etc I'm not 100% certain that I would be doing something that would make it any safer.
I'm all for trying to help someone out and save a few £ but not if I can't say with certainty that I would be leaving a safety issue.
Thanks again.