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

"Trevor Smith" wrote in message
...
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.

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.

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

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

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

SJW
Please reply to group or use 'usenet' in email subject

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


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


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

My laptop doesn't

Lee
--
Email address is valid, but is unlikely to be read.

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

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


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

My laptop doesn't

Smartarse!
--

SJW
Please reply to group or use 'usenet' in email subject

"Lurch" wrote in message
news
On Sat, 08 Jan 2005 01:19:59 +0000, Lee
strung together this:

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


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

My laptop doesn't

Smartarse!


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.

"BigWallop" wrote in message
...

"Lurch" wrote in message
news
On Sat, 08 Jan 2005 01:19:59 +0000, Lee
strung together this:

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


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

My laptop doesn't

Smartarse!


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.



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

Stephen Dawson wrote:
"BigWallop" wrote in message
...

"Lurch" wrote in message
news
On Sat, 08 Jan 2005 01:19:59 +0000, Lee

strung together this:

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


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

My laptop doesn't

Smartarse!

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



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

Lurch wrote:

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


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


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

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...

In article ,
Lee wrote:
Which ones are these then? Can't say as I've seen one.

My laptop doesn't

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.

--
*Two wrongs are only the beginning *

Dave Plowman London SW
To e-mail, change noise into sound.

"Stephen Dawson" wrote in message
...

"BigWallop" wrote in message
...

snipped

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


And what happens when the main earth conductor becomes separated?

Stephen Dawson wrote:

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.

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

(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.

This is to remove the potential leakage current associated with
switch mode psu's.

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

--
Andy

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
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

"BigWallop" wrote in message
k...

"Stephen Dawson" wrote in message
...

"BigWallop" wrote in message
...

snipped

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


And what happens when the main earth conductor becomes separated?



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

"Stephen Dawson" wrote in message
...

"BigWallop" wrote in message
k...

"Stephen Dawson" wrote in message
...

"BigWallop" wrote in message
...

snipped

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


And what happens when the main earth conductor becomes separated?



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



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.

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

However a
main earth is less likely to fall off than a single strand in the back of a
socket.

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

SJW
Please reply to group or use 'usenet' in email subject

On Sat, 8 Jan 2005 19:34:54 -0000, "Trevor Smith"
strung together this:

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.

I got it in a council spec once and gave up trying to convince them of
the correct interpretation of the regs.
--

SJW
Please reply to group or use 'usenet' in email subject

On 8 Jan 2005 00:51:25 -0800, strung together
this:

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

Apparantly so.
--

SJW
Please reply to group or use 'usenet' in email subject