Electrical Earthing arrangements in older properties
 

What is the legal position regarding earthing arrangements for a (domestic)
property that has as its main earth, a connection to the income cold *water*
pipe. I know that this is not allowed by the regs (although I think it used to
be?). There are several houses I know of in this suburb area that have this as
the only earth. Does the use of an RCB on the CU make this acceptable or *must*
it be changed?. If it has to be changed, what to? I don't know if PME is
available here - if not how about earthing rods per propery? Although safety
comes first of course I guess this could start to get expensive especially in
that each such arrangement has to be retested/certfied by some organisation?

AFAIK there is no legal requirement to rectify things like this. Such
installations would fail a periodic electrical inspection & test though,
with the need to provide a proper means of earthing flagged as urgent.

Are you sure that you are not confusing a main bonding connection to the
water pipe (which is required) with the actual means of earthing - which
would usually be to the lead sheath of the supply cable (TN-S system) on
an old installation with underground cable feed.

PME (TN-C-S system) may be available (ask the local distribution network
operator), but would require new service cables to be installed.

If the supply is overhead then it's much more likely that there is no
earth. In that case the options are to add an earth electrode (TT
system) and RCDs or to upgrade to PME, if available. A single RCD is no
longer acceptable - there should be a 30 mA one protecting the socket
circuits and a 100 mA one for everything else - see the IEE On-Site
Guide for details.

--
Andy

mac wrote:
What is the legal position regarding earthing arrangements for a (domestic)
property that has as its main earth, a connection to the income cold *water*
pipe. I know that this is not allowed by the regs (although I think it used to
be?). There are several houses I know of in this suburb area that have this as
the only earth. Does the use of an RCB on the CU make this acceptable or *must*
it be changed?. If it has to be changed, what to? I don't know if PME is
available here - if not how about earthing rods per propery? Although safety
comes first of course I guess this could start to get expensive especially in
that each such arrangement has to be retested/certfied by some organisation?


there are proably milions of propertes like this. As long a your water
supply remains metal, its normally a non issue. Metal water pipes make
excellant earths. However if the pipe upto the house is ever replaced
with plastic, you've got a real problem, and the installation could
become dangerous in some cases.

Simplest solution if youve got plastic water pipe is to add an earth
rod and connect it to the existing earth - dont undo whats there.


NT

mac wrote:
What is the legal position regarding earthing arrangements for a (domestic)
property that has as its main earth, a connection to the income cold *water*
pipe. I know that this is not allowed by the regs (although I think it used to
be?). There are several houses I know of in this suburb area that have this as
the only earth. Does the use of an RCB on the CU make this acceptable or *must*
it be changed?. If it has to be changed, what to? I don't know if PME is
available here - if not how about earthing rods per propery? Although safety
comes first of course I guess this could start to get expensive especially in
that each such arrangement has to be retested/certfied by some organisation?


there are proably milions of propertes like this. As long a your water
supply remains metal, its normally a non issue. Metal water pipes make
excellant earths. However if the pipe upto the house is ever replaced
with plastic, you've got a real problem, and the installation could
become dangerous in some cases.

Simplest solution if youve got plastic water pipe is to add an earth
rod and connect it to the existing earth - dont undo whats there. Note
that if relying on an earth rod, RCD or ELCB protection will be needed.


NT

wrote in message
ups.com...
mac wrote:
What is the legal position regarding earthing arrangements for a
(domestic)
property that has as its main earth, a connection to the income cold
*water*
pipe. I know that this is not allowed by the regs (although I think it
used to
be?). There are several houses I know of in this suburb area that have
this as
the only earth. Does the use of an RCB on the CU make this acceptable or
*must*
it be changed?. If it has to be changed, what to? I don't know if PME is
available here - if not how about earthing rods per propery? Although
safety
comes first of course I guess this could start to get expensive
especially in
that each such arrangement has to be retested/certfied by some
organisation?


there are proably milions of propertes like this. As long a your water
supply remains metal, its normally a non issue. Metal water pipes make
excellant earths. However if the pipe upto the house is ever replaced
with plastic, you've got a real problem, and the installation could
become dangerous in some cases.

Simplest solution if youve got plastic water pipe is to add an earth
rod and connect it to the existing earth - dont undo whats there. Note
that if relying on an earth rod, RCD or ELCB protection will be needed.


NT


The argument against relying upon a service for an earth is that the
material used can be changed on a whim by the service company at any time
and is not under your control.

"mac" wrote in message
...
On Thu, 06 Oct 2005 07:53:24 GMT, mac wrote:

As a followup to my followup, what does the earth cable from an earth
electrode
normally/prefferably terminate in? Is there a large block of copper called
? -
or does it usually go straight into the cu earth connector?

AFAICR it *has* to go straight to the CU connector without intervening
connections that might work loose and be hidden. Not sure if this is a
strong recommendation or law though. (I had to run a long one out of sight a
while ago).


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

mac wrote:

On Thu, 06 Oct 2005 07:53:24 GMT, mac wrote:

As a followup to my followup, what does the earth cable from an earth electrode
normally/prefferably terminate in? Is there a large block of copper called ? -
or does it usually go straight into the cu earth connector?

Well it goes to the "main earth terminal" - usually one of these
http://www.tlc-direct.co.uk/Main_Index/Earthing_Index/Earth_Blocks/index.html
but it can also be the earth bar inside the consumer unit. The main
bonding conductors to water and gas etc. must go to the same terminal.

--
Andy