RCCD in meter box randomly tripping

[JohnW2]

From that SWA, the black would be earth and I assume the grey is a sleeve over the steel armour.

Are you sure? It looks very much like a core to me - and I would have thought that blue/brown/black would be very unusual colours for 3-core SWA wouldn't they?

I guess these both go to the MET where they hold hands with the conductor from the earth rod.

The grey clearly doesn't go to the same place (the Henley, whether that's being used as the 'MET' or not) as the (G/Y taped) black.

A piccie which showed us where that grey goes would probably be helpful.

Kind Regards, John

 

[AndyPRK]

I think we all know that the armour isn't connected to the cpc.

 

[Taylortwocities]

I have heat shrink sleeving that would make it look a lot like that.
We need a picture of where those go to.

 

[JohnW2]

I have heat shrink sleeving that would make it look a lot like that.

So do a lot of us - but could you source blue/brown/black 3-core SWA, and could you make the heat-shrinked armour look as neat as that (and like a core) where it emerges from the cable? I don't think I could do either.

We need a picture of where those go to.

Indeed - as I said. My money would probably be on it going 'nowhere' A photo of the termination of the other end of the SWA would obviously be interesting - to tell us whether the armour is earthed at all.

Kind Regards, John

 

[FrogParty]

The grey core to clarify....

Can you confirm if the Grey core is unused or concerted to something else?

A piccie which showed us where that grey goes would probably be helpful.

The SWA is 4-core (blue/black/brown/grey), the grey core is unused and simply tapped off at either end, just out of shot in the photo (sorry).

At one time this extra core was also attached to the earth at the meter box end but not the other, this was changed in case it was contributing but the trips continued a day later so presumed to be a red herring.

The armour of the SWA doesn't appear to be earthed at the supply end

Should it be??

Also was the new RCCB tested or just put in could be that the new unit is actually faulty and not tripping when its meant to

Good point, but yes AFAIK it was tested.

you say its a TT system, with the earth at the cut out it would appear that there is some sort of DNO earth provided, if your on your own transformer this could be a TNS

Definitely TT. The Yellow/Green wire runs off out the meter box to a metal rod stuck into the ground.

If this were done properly the SWA should be terminated in a gland

Sorry, not sure what a "gland" looks like or what it does. These wires seem securely attached, no strain on them etc.

There also doesn't appear to be any over current protection between the meter & the SWA ..... which there should be!

That sounds worrying. Does the Legrand RCD not provide this? If I remember correctly I'm sure the electrician said it provided over current protection when he explained why we had to have a trip their at all. Then again doesn't the DNO provided fuse give that protection? Can someone that knows what they are reading check out part no 6027 11. What items should be fitted here, name the products and I'll challenge my electricians!

 

[JohnW2]

The SWA is 4-core (blue/black/brown/grey), the grey core is unused and simply tapped off at either end, just out of shot in the photo (sorry).

As I expected - pity I didn't 'put my money on it' Thanks for confirming!

At one time this extra core was also attached to the earth at the meter box end but not the other, this was changed in case it was contributing but the trips continued a day later so presumed to be a red herring.

I suppose it doesn't really matter what you do with it. Given thatit exists, if it were me I'd probably connect it with the black at both ends (with G/Y sleeving/taping).

The armour of the SWA doesn't appear to be earthed at the supply end

Should it be??

The armour must be earthed at least at one end, and the supply end would seem the most obvious. Is it earthed at the other end - and, if so, to what?

There also doesn't appear to be any over current protection between the meter & the SWA ..... which there should be!

That sounds worrying. Does the Legrand RCD not provide this? If I remember correctly I'm sure the electrician said it provided over current protection when he explained why we had to have a trip their at all.

Nope. That RCD is just an RCD (providing protection only against 'earth leakage' and provides no over-current protection. As you say, that is worrying.

Then again doesn't the DNO provided fuse give that protection?

The DNO's fuse is not intended to protect distribution cables within your installation and, depending upon the size of the SWA, may not provide adequate protection anyway. Given that you have a TT installation, you need that RCD, but you also need a 'switch fuse' to protect the SWA.

Kind Regards, John

 

[FrogParty]

Lots of simultaneous posting, thank you all for your interest and advice!

The armour must be earthed at least at one end, and the supply end would seem the most obvious. Is it earthed at the other end - and, if so, to what?

Given that you have a TT installation, you need that RCD, but you also need a 'switch fuse' to protect the SWA.

I will ask the electricians about both of these when I next see them, hopefully sometime this week.