Tony Williams wrote in message ...
In article ,
wrote:

I too am a bit perturbed by the apparent setup, with both an
olde-worlde voltage-operated earth leakage breaker, and a
whole-house current-balance one downstream. And as both Nick T
and Dave P have suggested, I'd want to ditch the voltage-operated
item.

The RCCB in the CU only feeds the three ring mains and the shower.
The appliances with fixed wiring (cooker, c/heating boiler,
immersion, lights, etc), are not on that 30mA RCCB and their
possible earth leakages would be detected by the old Chilton.
It makes a sort of sense.

Trust me, it doesn't. Its not nearly as simple as you just suggested.
Mixing a v-ELCB and an unbonded electric shower is not too clever.

So I hacked an old portable RCCB into a differential current
sensor, and have been going around the house looking for
possible (multiple) perps.

You have a fundamental installation problem and need it sorting out.
You might also have a faulty appliance, but that's secondary. Someone
needs to carefully look over your earthing system.

With a v-ELCB in circuit and tripping you will almost certainly have
no real earth in the place, and you may also have voltage
differentials sufficient to cause electrocution in more vulnerable
situations where human and water mix.

Understand this: the v-ELCB disconnects the whole house earth system
in order to function. Its how it works. Your house earth loop must
still be unearthed if the Chilton is tripping.

The basic use of the obsolete v-ELCBs is only secondarily for
additional protection against small earth leaks, its primarily to make
installations safe when there is an inadequate earth. When I say safe,
I mean for obsolete values of safe, and in no way safe for use with an
electric shower.

A v-ELCB on a wiring system is cause for caution. There are real
issues with them. They allow some types of dangerous situations to
occur without tripping.


The biggest perp (oh buggerit!) is this computer system. It
has a differential current of 1.3mA.

normal.


The number of nuisance trips have reduced over the last few
days (to zero yesterday). This may (or may not) be due to two
changes made. That VDR across L-E has been removed, and the
soil around the earthing rod has been thoroughly wetted (this
is a clay soil, which I know to be bone dry down to at least
3ft, with major cracks running through it).

Touch wood.....

Thanks for all the suggestions.

I've got to ask, are you still taking electric showers?


Regards, NT