On 28/04/17 18:22, ARW wrote:

Sufficient to trip a 30mA RCD.

Thanks Adam.


Which of course may might when then the electrician did the work but may
fail when some pipework is altered (and that pipework need not be in the
bathroom).

Local supplementary bonding removes that risk.

I agree that it's more foolproof in general (with the caveats that it's
not always easy to inspect once things are panelled in).

I'm happy with my house being sans SB as it was designed with that in
mind from the get go, but I do have cross bonding straps in the cupboard
where the pipes disappear off to the bathroom - mostly to ensure
continuity remains between hot, cold and heating pipes (when they exist)
and are not reliant on the boiler manifold (when it exists) to achieve this.

I also test loop impedance is sufficient to trip the relevant MCBs in
0.4sec - I am surprised that was not written into the regs as it would
have reduced the reliance on the RCD element.

That's more identifying a likely scenario where things might get
buggered up (eg boiler removed or replaced) and dealing with that rather
than any book standard approach.

I was keen to avoid SB as I have all my pipes on show - but if that
weren't a consideration, I'd have put it in conventionally.

In fact I will possibly build SB into the shower room as the pipes are
mostly bunched in the underbasin cupboard.