Functional earth on a RCBO, can it be connected to the DNO earth with a TN-C-S supply.

[AndyPRK]

I’ve just opened a wylex RCD 80A? Type A

Just seams to have a toroid and test resistor from what I can see

 

[ericmark]

I agree, but as said loss of PEN rare, and loss of just neutral even less likely, as to volts to hold in a RCD, we had some generators on the T5 job, which sensed the current, so would drop to tick over with no load, and the RCD's opened and the mag mount drill fell off.

It was 55-0-55 volt, and we had a talk about should we have RCD protection on 55-0-55 with items like mag mount drill, but my accident happened before we had assessed the risk.

 

[JohnW2]

I’ve just opened a wylex RCD 80A? Type A .... Just seams to have a toroid and test resistor from what I can see

That rather surprises me. How old is it?

 

[JohnW2]

I agree, but as said loss of PEN rare, and loss of just neutral even less likely, ...

With suoplies other than TN-C-S, I would have though that ";oss of just neutral" was just as likely as "loss of PEN" in a TN-C-S one, isn't it?

as to volts to hold in a RCD, we had some generators on the T5 job, which sensed the current, so would drop to tick over with no load, and the RCD's opened and the mag mount drill fell off.

I don't think that it can be like that with the active RCDs we see in a domestic context, since I think they disconnect in the event of power loss even if no current is flowing.

 

[AndyPRK]

That rather surprises me. How old is it?

Being a Type A, it’s not that old! When did 18th come in?

 

[JohnW2]

Being a Type A, it’s not that old! When did 18th come in?

2018 - about 6 years ago

 

[JohnW2]

I’ve just opened a wylex RCD 80A? Type A .... Just seams to have a toroid and test resistor from what I can see

This is the contents of one which 'blew up' due to an L-N short (hence all the soot). It's a Type AC installed around 2001/2,and the PCB with the electronics can be just about seen through the soot! ...

 

[AndyPRK]

Humm.
terminals look different.

Live power wire seams to be red on mine

Maybe I’ll dig a little deeper sometime

 

[JohnW2]

Humm. terminals look different. Live power wire seams to be red on mine ... Maybe I’ll dig a little deeper sometime

I presume that those 'wires' count as 'flex', so should have been brown/blue (as in mine) long befoore 2000. This is what it was (not the world's most reputable brand!) ...

 

[ericmark]

With suoplies other than TN-C-S, I would have though that ";oss of just neutral" was just as likely as "loss of PEN" in a TN-C-S one, isn't it?

Yes but there are far more TN-C-S than TN-S and TT.

 

[JohnW2]

Yes but there are far more TN-C-S than TN-S and TT.

Perhaps. We are certainly heading in that direction.

However, I don't think TN-C-S existed until around the 70s, so it will only be in installations first installed after then, or ones which have been 'upgraded' (e.g. cheapskate 'repair' of failed TN-S ). For what it's worth, of all the houses with which I'm most familiar (mine and family members') none have TN-C-S.

 

[flameport]

Hager RCBO, compact type with solid neutral.