Regulation 607 query

[Trevor Smith]

A friend of mine is moving to a new office and it is being rewired by a local company whilst I am fitting in the computer network and alarm, the thing is the contractor is now running 4mm earths to all the sockets. now I have looked into section 607 as I was going to do the rewire originally (pre part p) and the way I read it the min earth size is 1.5mm, now there will only be eight computers in the office so surely 4mm is a bit over the top or have I read the regs wrong so I am hoping the one of you more learned sparks out there could put me right.

Trevor Smith

[Mike]

The earth sounds OTT but I'll leave that to the pros to comment.

However some computers don't even have an earth wire nowadays.

[Lurch]

On Sat, 8 Jan 2005 00:12:48 -0000, "Mike" strung together this:

Which ones are these then? Can't say as I've seen one.

[Lee]

My laptop doesn't :p

Lee

[Lurch]

On Sat, 08 Jan 2005 01:19:59 +0000, Lee strung together this:

Smartarse!

[BigWallop]

Laptops are the only PC's I've seen that don't have an earth conductor from their separate power supplies. Anything in a metal casing, without double insulated skins over the hot spots, needs an earth wire. It's da rools, man.

[Stephen Dawson]

It is a misinterpretation of the rules for high integrity earthing systems for circuits supplying IT equipemnt. What should be being done is each connection of the cpc should be mechanically seperate from the other, i.e. one cable one terminal. The theory is that should one cpc become disconnected in an accessory then the other is still good. This is to remove the potential leakage current associated with switch mode psu's.

Stephen Dawson Fox Electrical Servcices Ltd

07970 940637

[deckertim]

I thought that part p only applied to domestic premises. If so, you could have done the job.

conductor

[The Natural Philosopher]

Certanly teh laptops we had that blew other compueter serial ports when we connected them, as the chassis wasn't earthed, and the RFI filters held them at a nice steady 110vAC WRT to earth...

[Dave Plowman (News)]

Strangely, I heard of a new one the other day which had. And caused an earth loop when coupled up to an external sound system.

[N. Thornton]

Fwom:BigWallop (spam.guard@_spam_guard.com)

conductor from

It is da roolz, but they arent enforced or applied. Open up any metal cased Japanese stereo, and 9 times out of 10 you'll find theyre single inulsated and unearthed.

NT

[Dave Plowman (News)]

Which makes? Repaired an NAD recently, and they'd gone to fair old lengths to make it safe with the top cover removed.

Lots of older Jap gear did have an earth for the UK - and suffered from earth loops because of them.

[BigWallop]

And what happens when the main earth conductor becomes separated?

[Capitol]

N. Thornton wrote: Open up any metal

Metal cased VCRs get their double insulation from the PSU and are unearthed. I can't see why PCs should be any different with a similar construction.

Regards Capitol

[Andy Wade]

That's only one of the permitted options for meeting Section 607. Briefly, all the options allowed by Reg. 607-02-04 are:

(i) Single CPC of at least 10mm^2;

(ii) Single mechanically protected copper CPC of at least 4mm^2;

(iii) Two separate CPCs, each complying with the normal requirements (Section 543), with independent connections throughout.

(iv) Use of an earth monitoring system to BS 4444, with automatic disconnection of supply if the CPC is detected to go o/c;

(v) use of an isolating transformer (etc.) in conjunction with one of the above.

Option (iii), used with a ring circuit, is the most common (with (i) or (ii) used for any spurs). In this case it sounds as if method (ii) was being used.

And the associated filters. And it doesn't remove the leakage current of course, just reduces the likelihood of it causing danger.

[Andy Wade]

That's rubbish, Sir.

"The rules" here means the EU 'low-voltage directive', implemented in the UK in the form of the Electrical Equipment (Safety) Regulations

1994. These are most certainly applied and enforced. The relevant product safety standard for the equipment you mention is BS EN 60065 (aka BS 415).

On Class 2 (non-earthed) equipment you should find both the CE mark and the 'double-square' symbol, which indicates Class 2 construction. Class

2 does not necessarily require double insulation; reinforced insulation will also meet the requirements of the standard.

[Trevor Smith]

Yes I was aware of using sockets with two earth points and separating the earths from the ring into two separate terminals on the earth bar in the C/U, it's the fact they are using a ring of 4mm earth cable as well as the earth that's in the twin & earth cable.

Trevor Smith

[Stephen Dawson]

Excatly the question we asked which made a mockery of the rule. However a main earth is less likely to fall off than a single strand in the back of a socket.

Steve Dawson

[BigWallop]

Oh Good !!! Because it happened on one of our sites and luckily the T&E earth centre was still there. I still can't get the culprit to own up on it, but someone must have loosened the main 4 mm earth from the terminal, because, even you said it, it is less likely to fall out than the single conductors in the sockets.

[Lurch]

On Sat, 08 Jan 2005 20:39:20 GMT, "Stephen Dawson" strung together this:

I wouldn't have said so. I've seen as many bad distribution boards as I have sockets. (IME)