Supply earth

[derekandco]

Hi.
I,ve just bought a 1930s house and I am going for a full re-wire. The electrician doing the work tells me that the existing supply earth is via an earth clip on the supply sheath, and that this will not "do" for the new installation and it will have to be changed by the supply company. He has gone on holiday till the new year, and as I want to get on with things I want to get it sorted before he comes back. Who do I contact (I'm in South Wales) and any ideas as to how much it might cost.
Thanks. Derek

 

[westie101]

Why does it need to be changed (did he tell you that)?

The earth meets the specs of the DNO and is not covered by BS7671 so is perfectly OK. Having said that the DNO may change it if you ask!

 

[Adam_151]

I always comment on them as such a use is not in compliance with BS591 to which the bonding clamps are manufacturered

 

[westie101]

Whilst I can't speak for the DNO in your area, we would rather the electrician contact us to save on confusion

 

[chivers67]

Derek, did the electrician use any test equipment of any sort or was it purely visual?

 

[jzaw]

Derek, did the electrician use any test equipment of any sort or was it purely visual?

we recently had solar pv installed and the 'leccy used a MEGGER to test many parameters including earth impedance and max fault current it might be able to pass etc

megger 17th ed testers

he did this specifically cos I had suspected that I might have an earth fault or other

nothing of the sort

everything checked out fine despite LOOKING a bit poor ... the earth wire is a 1950's somewhat slim looking cable with no sheath (now shrunk wrapped with green/yellow) and soldered into the outer sheath of the incoming supply cable

LOOKS can deceive so get it properly metered and measured and then you can rest more easily

 

[ban-all-sheds]

Think hard about where to have sockets - it's difficult to have too many, and also about what circuits to have. The items on the list below won't all apply to you, but they are worth thinking about:

• Upstairs sockets
• Downstairs sockets (or a L/R or front/rear split)
• Kitchen sockets
• Circuit for appliances
• Cooker circuit
• Non-RCD circuit for F/F
• Non-RCD circuit for CH boiler
• Dedicated circuit for hifi
• Dedicated circuit for IT equipment
• Upstairs lights
• Downstairs lights
• Lighting circuits with switches in the usual places but with 2A/5A round pin sockets at low level.
• Immersion heater
• Loft lights
• Shower
• Bathroom circuit
• Alarms
• Supply for outside lights
• Supply for garden electrics
• Supply for shed/garage

Plus any peculiarities brought about by your house layout & construction - e.g. in mine because of solid floors and where the socket circuits run, I have a radial just for a socket in the hall, the doorbell and the porch lights.

Unless you want to go to the expense of RCBOs throughout, the CU should have at least 3 sections, 2 on RCDs and one not into which you can install a mix of RCBOs and MCBs.

It can be a good idea to put all wiring in conduit for ease of future changes. And if you specify metal conduit for switch drops, or BS 8436 cable it removes the need to have RCDs where you'd rather not.

If you live somewhere where supplies are dodgy in the winter, have the lights, the boiler supply, and a socket in each room wired to a separate CU, or a separate section in a large one, that can be supplied by an emergency generator - lights, heating, TV and a kettle/microwave make life a lot more bearable.

Flood-wiring with Cat6 or Cat6a cable is worth thinking about.

 

[sparkwright]

Hi.
I,ve just bought a 1930s house and I am going for a full re-wire. The electrician doing the work tells me that the existing supply earth is via an earth clip on the supply sheath, and that this will not "do" for the new installation and it will have to be changed by the supply company. He has gone on holiday till the new year, and as I want to get on with things I want to get it sorted before he comes back. Who do I contact (I'm in South Wales) and any ideas as to how much it might cost.
Thanks. Derek

I can't understand what your electrician is worried about.

It is usual for the electrician to replace the clamp and and upgrade the earth cable himself.

The only major problem normally is that possibly he has found a high Ze in the property, which would then become the responsibility of the DNO.

This would possibly be due to a breakdown in the cable sheath.

 

[ebee]

If he`s found that someone has put a bog standard BS951 earhclamp on rather than a soldered point or a constant pressure spring by the DNO then yes they are correct to get the DNO to change or (or Declare it TT or to say it is acceptable as is).

Actually I have seen loads like that without going bang but if youre electrician connects to it or tightens it a bit and it goes bang he probably feels he will get blamed.

 

[Lectrician]

Give Western Power Distribution a ring and ask them to confirm your earthing arrangements.

WPD would not fit a BS591 clamp to a lead sheathed cable, a braid would have been sweated on and terminated into a henley block for the customer.

These days they would likely provide you with an earth from the neutral, even on an old TN-S supply.

It sounds like a sparky may well have fitted a BS591 clamp to provide an earth themself, something which should not have been done.

 

[securespark]

It is usual for the electrician to replace the clamp and and upgrade the earth cable himself.

Not in my world!

You should not use pipe clamps to connect to cable. Imagine the bang if that goes wrong.

The DNO do work to different rules and may fit these themselves, but that's for them to decide, not "the electrician".

My advice would be to invite the DNO round to check the clamp, but they won't usually attend unless you have an out-of-spec Ze.

To the OP: What is the Ze?

 

[derekandco]

Hi . Thanks for all the replies. A mixed bag. I,ll wait till the electrician starts back as I can't answer your questions or the DNO,s about why it wont do. I just thought i might be able to move things on a bit.
Have a happy and prosperous new year!
Thanks again.
Derek.