Ron Lowe wrote:

Pedantic point, when does cable cease to be visible? If it is
enclosed in
surface run trunking or conduit I'd say it was still visible and
didn't need
additional protection. Is this how the 17th edition would view it?

I believe it would... surface wired, or in visible trunking / conduit
ought to be fairly immune to being nailed / screwed through (well at
least by accident anyway!)



How is cable dangling freely in an intenal cavity wall ( say 4x2 or
fatter ) considered?

If it was passing through holes in the studs at their centres then you
could argue it is = 50mm from the surface and hence not in need of
further protection.

Thanks for your previous answer, it's much as I suspected.

The actual reason I posted was this:

We are having major building work done, with a couple of extensions ( up
and out! )
This adds some new circuits.
Without asking, the electrian ripped out my '16th edition' M-G CU, (
with many spare slots ) and replaced it with a '17th edition' 'Sector'
brand whole-house RCD unit. We have a big house, with many appliances,
including a *lot* of computer equipment. This is nuisance-tripping up
to 5 times a day. I cannot determine any particular appliance or even
circuit that is causing this. It may not be an actual fault as such,
just a cumulation of normal leakages.

A whole house RCD is not compliant with the 17th edition. In a small
house with relatively few circuits you could get away with two RCDs -
one protecting say downstairs power and upstairs lighting, and the other
doing the inverse. On a larger install I would expect to see more RCDs
or RCBOs used on the non RCD side of a multi split board.

Is it too late to get the sparks back to do the job correctly?

We have just come back from a week's skiing to find a de-frosted freezer
and fridge. And my Humax PVR missed Wallace and Grommit. I'm not best
pleased.

Won't help the fridge, but iPlayer may still have W&G (if not, I have a
copy on Toppy I could stick on DVD for you!)

There may or may not be an earth fault. It might just be the
cumulation of normal earth leakages. Either way, I can't live with the
whole-house approach. RCBOs would limit the damage to one circuit, and
help fault-finding if a fault is indeed present.

Indeed - I can't see how he could have fitted a single RCD and proclaim
it to be compliant. It does not meet the basic requirements for
discrimination.

I have a meeting with the artichoke and builder shortly, and I'm going

(don't you just love spell checkers ;-)

to insist on changing the configuration away from the
cheapest-way-to-achieve-17th-edition-compliance-whole-house-RCD approach.

Yup - what you have is non compliant, and also completely unsuitable for
your circumstances.

To smooth things over, I'm going to offer to supply a new
fully-populated CU myself ( I have access to M-G stuff for less than 1/4
the list price of say £70 for an RCBO ), and just ask them to shove the
'Sector' whole-house CU where the sun doesn't shine.

Not been a great fan of the MG stuff to be honest - ever since meeting
some Proteous MCBs which had a mind of their own. I hope their own label
stuff is better.

Either way, Hager and Contactum both have single module RCBOs available
for under £25 these days.



--
Cheers,

John.

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