OT: Re house wiring earthing and other things.

My nephew is moving into a rented house. The old consumer unit has at some time been replaced with a more modern one with two RCDs and has two ring circuit MCBs - there is no separate ring for the kitchen. The earthing for the house appears to be via a wire which goes through a ventilation grill and dissapears into the ground, presumably connected to an earth rod.

Two questions: The earth wire mentioned appears to be a bit flimsy, certainly no more than 6mm and maybe only 4mm. Is this considered heavy enough?

Secondly: there is no earthing for the sink - a measurement to a nearby metal cooker socket switch using a digital multimeter gives a reading of around 20 ohms- given that the wiring does not use PME earthing, should the sink be bonded to earth or does the existing arrangement comply with the regulations?

Apparently my nephew was told that an electrical inspection made some time ago, (don't know how long ago), stated that the installation was satisfactory and the landlord - a county council - was not interested in his request for more sockets. The previous tenant got around the lack of sockets by using numerous four way extentions and multi plugs.

There is a lot of wiring which is simply clipped to the surface of the wall or along the top of skirting board with no protection. For instance two surface mounted sockets in the kitchen are wired in this way. Is this considered safe?

Thank in advance for any replies (especially re the sink earthing).

JohnT

Reply to
JohnT
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Kitchen sinks do not have to be bonded.

4 way extension are okay provided they are not cascaded/daisy-chained or used for high current appliances like heaters. You can get 6-8-10 way ones from some suppliers. Multiplug adaptors can be overloaded as they're unfused (at least the 2-plug ones are, the 3-plug ones should now be fused but older ones aren't) and can also cause poor contact leading to overheating.

Surface clipped wiring is acceptable provided it is visible and not where it is vulnerable to physical damage.

Owain

Reply to
Owain

It's heavy enough electrically, but if the same size is used underground (buried) without further protection then it does not meet current-day requirements for physical durability.

If the connection to the earth rod is above ground then 4mm^2 is OK. OTOH an insulated wire directly buried should be 16mm^2 minimum, unless it's protected by being run in suitable conduit or duct. It sounds as if whoever replaced the consumer unit may have neglected to bring the earthing conductor up to current standards. Also the connection to the earth rod, if it's made, as it probably is, by means of a mechanical clamp, should be accessible for inspection. This is usually achieved by the use of an 'earth pit' which will have a concrete or plastic cover marked "earth rod" or similar.

Reply to
Andy Wade

through a

connected to an

doesnt sound like therea any problem there.

NT

Reply to
bigcat

That's a point that is often debated. If the pipework to the sink is copper, and that is bonded, then the best advice I have received is that the sink should be bonded as well.

However if the sink is fed via plastic pipework then it doesn't need to be bonded.

I'm not suggesting you are wrong, it's simply that qualified sparks do tend to debate this issue and it's the best understanding I have come away with.

Andrew

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Reply to
Andrew McKay

Thanks for replies. Will pass the info onto my nephew. JohnT

Reply to
Over71

The *authoritative* sources make it totally clear that they *don't* need to be bonded. The IEE On-Site Guide's section 4.6, with a note in the margin pointing at Regulation 471-08-01, says thus (in full - so don't think I'm quoting selectively):

4.6 Supplementary Bonding in othe Locations - Metal Pipework

There is no specfic requirement in BS 7671 to supplementary bond the following

kitchen pipes, sinks or draining boards

metal furniture in kitchens

metal pipes and wash hand basins in domestic locations other than bathrooms

[and in smaller print,] Note: metal waste pipes in contact with earth should be main bonded back to the main earthing terminal.

But there's a widely-read Guide To The Regs by Whitfield which *does* claim that sinks should be bonded; the electrical wholesalers CPC make this book available on-line, and the relevant bit is at

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the author states that exposed metalwork should be bonded where its resistance to earth is under 50kohms: note that this is one commentator's hobbyhorse, rather than the Regs speaking. The counterargument, which Whitfield doesn't acknowledge, is that bonding to the supply earth can *increase* danger, by providing a (possibly greatly) increased current flow through a body in the presence of a fault. (This is how the MP's daughter died recently in the bizarre kitchen accident - a metal cutlery rack had been installed with a screw which some time after the installation finally made contact with the live conductor (only) of a misrouted cable; and though over the course of a few days more than one person had got a 'tingle' off it(!), it wasn't until the unfortunate victim touched it while her leg was pressed hard against an earthed (as it should've been) dishwasher that there was a low enough resistance to earth for the 'tingle' others had received (earth path through body, shoes, and flooring) became a fatal shock (earth path through body and metallic path to earth).

Stefek

Reply to
Stefek Zaba

Thanks Stefek - I think that clears it up nicely.

Andrew

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Reply to
Andrew McKay

Yes, there is such a wholesaler;

but it doesn't maintain the tlc-direct website. Strangely enuff, that's maintained by, umm, TLC.

Old age, that's what it is, old age...

Stefek

Reply to
Stefek Zaba

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