Why is there a 1 volt potential difference?

Wylex 240v, 50hz, 8A load, 100mA Trip, CAT.Wem 80/2 Current Operated Earth Leakage Circuit Breaker. Device must Switch off on testing if not seek advice ... Thanks John, because it doesn't say RCD I hadn't realized that that was what it was, but I see '100mA Trip, and 'Earth Leakage' so I think I had one without knowing?
It seems that you probably have - or almost (see below)

Should that perhaps be "80A load" (rather than "8A load")?

Is that all it says? No mention of "time-delayed", "TD" or "Type S"? If it is not a time-delayed one, that is not ideal. It means that a fault causing the RCD in the CU to trip might well cause that external RCD to trip as well, thereby taking out all your circuits (including the lighting ones), not just those circuits protected by the CU's RCD - which rather cancels the benefit of having a 'split' CU (with not all circuits protected by the same RCD).

Kind Regards, John

Yes well spotted John it is 80A not 8A.

So the stand alone RCD is safe, but it would hinder diagnosis of what caused the trip.

No John, no mention of 'TD' or 'Type S' so it probably isn't time delayed. So presumably I need it removed or replaced, another job for Scottish Power or SWEB (South West Electricity Board)
 
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All 3 tails goto the same place from what I can see.
Almost like the new grey tails were to replace or backup the old ones.
 
Two tails into one meter termination? That's bad practice. There really should be a 100A "Henley" block. And (per above) the fabric-covered tails could do with changing while he/she's at it.
Indeed, but I'm a bit confused - it looks as if the fabric-cover tailed tails and the PVC ones are in parallel, between the meter and RCD. If so, they need replacing by just one pair, of appropriate size!

Kind Regards, John
 
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Yes well spotted John it is 80A not 8A.
As I suspected :)
So the stand alone RCD is safe, but it would hinder diagnosis of what caused the trip. No John, no mention of 'TD' or 'Type S' so it probably isn't time delayed. So presumably I need it removed or replaced, another job for Scottish Power or SWEB (South West Electricity Board)
Yes, 'safe' in terms of providing adequate fault protection to all your circuits, which is (I presume) what Lectrician was primarily concerned about. The absence of a time-delay is not so much a matter of hindering diagnosis, but more a matter of the theoretical hazard it presents - because a fault on, say, a sockets circuit could result in the whole house being plunged into darkness, perhaps whilst you were up a ladder, holding a pan of boiling oil or whatever! It's a very small 'hazard', but since you need to get someone to sort out those tails, I would think that you might as well get the RCD changed to a time-delayed one at the same time (if you can't get upgraded to PME, in which case you wouldn't need that RCD at all).

Kind Regards, John
 
Indeed, but I'm a bit confused - it looks as if the fabric-cover tailed tails and the PVC ones are in parallel, between the meter and RCD. If so, they need replacing by just one pair, of appropriate size!

Kind Regards, John

Yes John the consumer unit and the cables feeding in and out look nice, although could do with having a second inbuilt RCD, but the meter tails are a mess.
 

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