Consumer Units with RCBOs

[PeterC]

Thanks, this clarifies it. There's only one cable that's diagonal and that is clipped to the surface - and avoided a re-wire.

[PeterC]

These were done by the original electricians. Next door had a shower pump taken from the lighting circuit that is on a

100mA RCD; that was done by a 'qualified' electrician (domestic and commercial).

[John Rumm]

Depending on the circumstances, that may be a sensible design decision.

The use of the 100mA RCD might be because the earthing system is TT and hence all circuits needed to be RCD protected (even in days before this was common) to ensure disconnection in the event of an earth fault.

If the pump is in a bathroom, there are quite possibly no other electrical circuits available near by, and the load from a pump is only likely to be a few hundred watts - so it will not stretch the supply. That's the same reason other small loads in bathrooms like extractor fans or shaver sockets are often fed from a lighting circuit.

[PeterC]

It's TN-C-S - updated about 25 years ago.

No circuits, but the taps are on copper pipe (mine's all plastic, so no Earth path) and the bonding's dodgey. My shower is off the 30mA RCD (same board and basic installation, done at the same time). Slightly worrying was that the pump was in a housing on the wall, the same as an electric shower, and the brushes were wearing out resulting in graphite visible around the joins and control - I don't know how conductive that would be. Perhaps best not to have the iron bath bonded to earth in this case.

[ARW]

Most shower pumps require a 30mA RCD supply.

[ARW]

You have not seen my cooker installs then:-)

[spuorgelgoog]

Mine is vertical - diagonal - vertical.

Installed by the builders, at least it's in conduit.

And at least since I moved in the conduit is now earthed.

Owain

[stephenten]

The diagonal cooker cables I see behind cookers are invariably under plastic capping... And is a single straight diagonal run.

So well done to the builder for using metal conduit and for you in earthing said conduit.....

[John Rumm]

These days yup... a historical install may not have specced it.

[ARW]

And you know my views on using a RCD as protection vs supplementary bonding.

[Adam Funk]

I don't but I'll bite --- why?

[ARW]

RCDs fail. Supplementary bonding doesn't.

[Adam Funk]

Fair point.