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Junior Member
 
Posts: 2
Default Earth provision after replacing water main with MDPE

I have recently replaced approx 3m of lead water main to the house with 25mm MDPE.

At the weekend I made the final coonection inside the house, and removed the lead tail and stopcock that previously served the house. When doing so I noticed an electrical wire attached to the lead pipe, and assume this has something to do with the earth for the electrics meter cupboard.

Do I need to provide anothe connection to earth. Should I extend the (now severed) wire back to the water board's supply, which is still in lead?

I think my gas has been sleeved in the last 18 months, so has that removed that earth component also?

As you can see, I'm quite confused about this whole earthing thing. Many thanks in anticipation.

Kevin, Oxford
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BigWallop
 
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"Kevin Brady" wrote in message
...

I have recently replaced approx 3m of lead water main to the house with
25mm MDPE.

At the weekend I made the final coonection inside the house, and
removed the lead tail and stopcock that previously served the house.
When doing so I noticed an electrical wire attached to the lead pipe,
and assume this has something to do with the earth for the electrics
meter cupboard.

Do I need to provide anothe connection to earth. Should I extend the
(now severed) wire back to the water board's supply, which is still in
lead?

I think my gas has been sleeved in the last 18 months, so has that
removed that earth component also?

As you can see, I'm quite confused about this whole earthing thing.
Many thanks in anticipation.

Kevin, Oxford

Kevin Brady


Where these earth points actually creating the main earth bonding for the
electrical supply? Or, were they just equipotential bonding to the gas and
water mains?

You'll know if you look at the electricity supply head end. Is there a big
thick earth wire provided from it, or close by it?


  #3   Report Post  
Christian McArdle
 
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When doing so I noticed an electrical wire attached to the lead pipe,
and assume this has something to do with the earth for the electrics
meter cupboard.


If you have copper pipework in the house, move the earth connection to the
where this takes over from the MDPE. Note that this isn't (at least
shouldn't!) be your main earth. It is just ensuring that the pipework has
the same earth potential as the rest of your house. The main earth is either
supplied by the electricity suppler via the cable sheath (TN-S) or via the
neutral (TN-C-S), or you will have an earth rod (TT) and every circuit will
be RCD protected.

If you have a older house, it is possible that you have an old system that
did rely on the water pipe to provide earthing and that now your house is
very dangerous. As you don't seem to know enough about electrical
installations to determine the type of earthing in use, I'd advise you post
a picture of your meter cupboard and consumer unit so you could get further
advice, as it should be obvious what type of earthing you have from the
supplier's installation. If this determines a TT system, you'll need to find
out if you have a good earth rod. Alternatively, just call out an
electrician who will test that the earthing is safe.

Do I need to provide anothe connection to earth. Should I extend the
(now severed) wire back to the water board's supply, which is still in
lead?


Unfortunately, it is a requirement that the cable is unbroken and unjointed.
If it not long enough to reach the copper part of your house plumbing, you
are up sh*t creek and will need to lay a fresh cable from the earthing
terminal, which might be not a nice job.

Christian.


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Kevin Brady
 
Posts: n/a
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Okay

I've just checked out my meter cupboard:

On the board with the meter (spinning wheel) is a junction block with three
yellow/green wires connected to it:

1 to the incoming mains cable, with a metal tag saying DO NOT REMOVE.
1 to the main fuseboard (not fuses but rcds - push button type)
1 to a seperate fuse box which supplies my soon-to-be-ripped-out electric
shower.

Does this help anyone, BigWallop, Christian?

Cheers

Kevin, Oxford




"Christian McArdle" wrote in message
. net...
When doing so I noticed an electrical wire attached to the lead pipe,
and assume this has something to do with the earth for the electrics
meter cupboard.


If you have copper pipework in the house, move the earth connection to the
where this takes over from the MDPE. Note that this isn't (at least
shouldn't!) be your main earth. It is just ensuring that the pipework has
the same earth potential as the rest of your house. The main earth is
either
supplied by the electricity suppler via the cable sheath (TN-S) or via the
neutral (TN-C-S), or you will have an earth rod (TT) and every circuit
will
be RCD protected.

If you have a older house, it is possible that you have an old system that
did rely on the water pipe to provide earthing and that now your house is
very dangerous. As you don't seem to know enough about electrical
installations to determine the type of earthing in use, I'd advise you
post
a picture of your meter cupboard and consumer unit so you could get
further
advice, as it should be obvious what type of earthing you have from the
supplier's installation. If this determines a TT system, you'll need to
find
out if you have a good earth rod. Alternatively, just call out an
electrician who will test that the earthing is safe.

Do I need to provide anothe connection to earth. Should I extend the
(now severed) wire back to the water board's supply, which is still in
lead?


Unfortunately, it is a requirement that the cable is unbroken and
unjointed.
If it not long enough to reach the copper part of your house plumbing, you
are up sh*t creek and will need to lay a fresh cable from the earthing
terminal, which might be not a nice job.

Christian.




  #5   Report Post  
Lurch
 
Posts: n/a
Default

On Mon, 10 Jan 2005 21:50:26 GMT, "Kevin Brady"
strung together this:

Does this help anyone,


Nope, I'd get someone in if I were you. You had all the info you
needed in the previous posts really.
--

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


  #6   Report Post  
BigWallop
 
Posts: n/a
Default


"Lurch" wrote in message
...
On Mon, 10 Jan 2005 21:50:26 GMT, "Kevin Brady"
strung together this:

Does this help anyone,


Nope, I'd get someone in if I were you. You had all the info you
needed in the previous posts really.


I'm with Lurch on this one as well Kevin. From what you describe, it is still
not clear where the main earth is coming from.

Contact your Leccy Supplier to check it for you.


  #7   Report Post  
Kevin Brady
 
Posts: n/a
Default

I thought this confirmed that the earth is routed to earth via the mains
sheathing, but I'll contact Southern Electric in the morning - thanks for
taking the time to respond.


"BigWallop" wrote in message
k...

"Lurch" wrote in message
...
On Mon, 10 Jan 2005 21:50:26 GMT, "Kevin Brady"
strung together this:

Does this help anyone,


Nope, I'd get someone in if I were you. You had all the info you
needed in the previous posts really.


I'm with Lurch on this one as well Kevin. From what you describe, it is
still
not clear where the main earth is coming from.

Contact your Leccy Supplier to check it for you.




  #8   Report Post  
 
Posts: n/a
Default


Christian McArdle wrote:
When doing so I noticed an electrical wire attached to the lead

pipe,
and assume this has something to do with the earth for the

electrics
meter cupboard.


If you have copper pipework in the house, move the earth connection

to the
where this takes over from the MDPE. Note that this isn't (at least
shouldn't!) be your main earth. It is just ensuring that the pipework

has
the same earth potential as the rest of your house. The main earth is

either
supplied by the electricity suppler via the cable sheath (TN-S) or

via the
neutral (TN-C-S), or you will have an earth rod (TT) and every

circuit will
be RCD protected.

If you have a older house, it is possible that you have an old system

that
did rely on the water pipe to provide earthing and that now your

house is
very dangerous. As you don't seem to know enough about electrical
installations to determine the type of earthing in use, I'd advise

you post
a picture of your meter cupboard and consumer unit so you could get

further
advice, as it should be obvious what type of earthing you have from

the
supplier's installation. If this determines a TT system, you'll need

to find
out if you have a good earth rod. Alternatively, just call out an
electrician who will test that the earthing is safe.

Do I need to provide anothe connection to earth. Should I extend

the
(now severed) wire back to the water board's supply, which is still

in
lead?


Unfortunately, it is a requirement that the cable is unbroken and

unjointed.
If it not long enough to reach the copper part of your house

plumbing, you
are up sh*t creek and will need to lay a fresh cable from the

earthing
terminal, which might be not a nice job.

Christian.



I recently did a similar task - replacing the incoming lead pipe with
plastic, though being an elderly property there was no grounding wire.
Now the earth for the house is at the back of the property and
water-pipe-in is at the front and as far from the earth pin as it could
be. Am I really required to bond the piping at the house entry point
which will be seriously difficult to get to, a considerable length and
is totally at one extreme of the piping system, or can I take the
bonding wire to say the cold water tank which is central, is a
relatively short run and is easy access.

Rob

  #9   Report Post  
Andy Wade
 
Posts: n/a
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Kevin Brady wrote:

I thought this confirmed that the earth is routed to earth via the mains
sheathing, [...]


Well that's what I thought too. You said

1 to the incoming mains cable, with a metal tag saying DO NOT REMOVE.


which seems fairly clear evidence for a TN-S earth to the service cable.
You just need to move the original water bonding connection onto your
copper pipework as near as practicable to the stop-cock and you're done.

Oh, and also

main fuseboard (not fuses but rcds - push button type)


them's MCBs not RCDs.

--
Andy
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BigWallop
 
Posts: n/a
Default


"Andy Wade" wrote in message
...
Kevin Brady wrote:

I thought this confirmed that the earth is routed to earth via the mains
sheathing, [...]


Well that's what I thought too. You said

1 to the incoming mains cable, with a metal tag saying DO NOT REMOVE.


which seems fairly clear evidence for a TN-S earth to the service cable.
You just need to move the original water bonding connection onto your
copper pipework as near as practicable to the stop-cock and you're done.

Oh, and also

main fuseboard (not fuses but rcds - push button type)


them's MCBs not RCDs.

Andy


It doesn't really prove a TN-S supply Andy. The tag around the supply cable
might also be just an equipotential bonding of the steel wire armour. So I'd
still say stick with contacting the Leccy Supplier, because they to might have
been using the pipework as their main earth.




  #11   Report Post  
Stefek Zaba
 
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Andy Wade wrote:
Kevin Brady wrote:

I thought this confirmed that the earth is routed to earth via the
mains sheathing, [...]



Well that's what I thought too. You said

1 to the incoming mains cable, with a metal tag saying DO NOT REMOVE.


which seems fairly clear evidence for a TN-S earth to the service cable.
You just need to move the original water bonding connection onto your
copper pipework as near as practicable to the stop-cock and you're done.

That's how it read to me too - not that it'll hurt the OP to *try*
phoning their supplier and asking what their records show as the
earthing type they've provided... but the chance of getting a sensible
answer out of the mess of supply-cos, meter-readers, and bill-issuers is
not my idea of a fun time. And of course the OP'll be safest if they
call out a sparks, but it's not that likely they have anything other
than an earth supplied by the incoming supply sheath. For the call-out
charge they'd be better off getting a periodic inspection report done,
which would include a look at the earthing...

Stefek
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Stefek Zaba
 
Posts: n/a
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I recently did a similar task - replacing the incoming lead pipe with
plastic, though being an elderly property there was no grounding wire.
Now the earth for the house is at the back of the property and
water-pipe-in is at the front and as far from the earth pin as it could
be. Am I really required to bond the piping at the house entry point
which will be seriously difficult to get to, a considerable length and
is totally at one extreme of the piping system, or can I take the
bonding wire to say the cold water tank which is central, is a
relatively short run and is easy access.

As I understand it, you really are supposed to run the main
equipotential bonding to the entry point of the services, or to the
point at which they start being metallic. I'm guessing - and it's only
that - the thinking is this is the point least likely to be monkeyed
about with, whereas bonding to something like your main tank is more
likely to get disconnected either temporarily or permanently if
maintainance work is done on the tank or whatever other "less
permananent" bit of the water installation you might choose. And,
pragmatically, that's where an Inspecting Sparks doing a periodic
inspection/house-sale-inspection will look for the main bonding.

That said, the truly important thing for safety is that your pipework is
bonded. If it's more convenient "for now" to run a bond to the tank, or
a part of the rising main or other
"bound-to-be-in-good-contact-with-all-the-pipework" point, I couldn't
blame you for bonding there "for now", while promising yourself to run
the conventional, Regs-compliant bond to the water entry point when some
round tuits accumulate. But don't rely on this random set of bytes in a
Usenet posting, apparently from someone you've never met, in case
someone visiting your place gets electrocuted and you're held negligent
for non-conformant bonding!

You do know, don't you, that the bonding needs to run unbroken (though
it can "visit" multiple bonding points on the way, just don't cut it)
back to the main earthing terminal next to your CU, not to the earth rod
you appear to have (the "earth pin")? Does that make it easier to reach?
I.e., the main bonding conductors to your other metallic services run to
an earthing bar by your CU, and the conductor to your earth rod then
runs from there. Also, that there's nothing stopping you running a
thick-enough (10mmsq, from memory) bonding conductor round the outside
of your house, and back in to the water riser? (Thickness needed here
because it's not mechanically protected, most of all - if you ran it in
conduit a thinner one *might* be acceptable on the TT setup you seem to
have, but I'd defer to someone who knows properly rather than trust to
this random collection of bytes etc etc!)

HTH - Stefek
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Andy Wade
 
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Stefek Zaba wrote:

As I understand it, you really are supposed to run the main
equipotential bonding to the entry point of the services, or to the
point at which they start being metallic. I'm guessing - and it's only
that - the thinking is this is the point least likely to be monkeyed
about with, whereas bonding to something like your main tank is more
likely to get disconnected either temporarily or permanently if
maintainance work is done on the tank or whatever other "less
permananent" bit of the water installation you might choose.


I'd say it's more a case of equalising any potential difference (PD)
between the incoming service, which will be in contact with the local
ground, and the TN 'mains earth' provide by the supplier, which might
not be at local ground potential if there's a fault on the supply
network. Bonding other than at the point of entry runs the risk of an
unbonded locally-grounded section of metalwork being left in place if a
section of the plumbing (etc.) between the entry point and the bonding
point is replaced in plastic.

The aim of bonding is not "to earth all your plumbing" and it does not
matter if there are plastic bits after the main bond at the point of
entry. In the high-risk areas supplementary bonding is there to prevent
any localised PDs appearing.

And, pragmatically, that's where an Inspecting Sparks doing a
periodic inspection/house-sale-inspection will look for the main
bonding.


Absolument Monsieur.

You do know, don't you, that the bonding needs to run unbroken (though
it can "visit" multiple bonding points on the way, just don't cut it)


That's one of those 'requirements' that people like to make up - it's
not in BS 7671. There's no objection to joints in bonding conductors;
the normal rules for connections (and their accessibility) apply.

Also, that there's nothing stopping you running a thick-enough
(10mmsq, from memory) bonding conductor round the outside of your
house, and back in to the water riser? (Thickness needed here because
it's not mechanically protected, most of all - if you ran it in
conduit a thinner one *might* be acceptable on the TT setup you seem
to have,


If not buried the smallest size would be 6mm^2 for the main bonding and
4mm^2 for an unprotected TT earthing conductor. The latter, if a buried
insulated wire (6491X), increases to 16mm^2. I tend to use and
recommend 16mm^2 for any main earthing & bonding - as you say you don't
want anything too feeble.

--
Andy
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