I don't have any metal pipework coming into my house. The water supply
is plastic - followed by a short length of copper, then speedfit. All
waste pipes are plastic. The only metallic object that could
conceivably be in contact with "earth" is my stove (which does my
central heating) which is sat on the ground, arguably making the
bathroom towel rails extraneous conductive parts.

As far as I can tell, I have nothing to main bond, which means all my
main bonding is in place. The electrician disagrees. He thinks that as
I have no bonding, it is not in place. He also wants to bond the
short length of copper pipe attached to the plastic water supply for
some reason.

It seems that whether or not main bonding is regarded as being in
place has implications for supplementary bonding. Due to the
configuration of the bathrooms, I think the easiest and most sensible
way to supplementary bond in my situation is to run a cable from the
towel rails to the consumer unit, letting the CPCs do the rest. In
fact I don't think even that is necessary (bathrooms are on RCBOs),
but don't mind a bit of belt and braces. I don't see the point in
doing any more, but the electrician seems to want to put a lot more
in!

The electrician says his mate who is going to "Part P" the work for
him insists on all the bonding. So who's right - the sparky or me?

On Wed, 08 Apr 2009 23:44:59 -0700, tom.harrigan wrote:

I don't have any metal pipework coming into my house.

Are you all electric then? No gas or oil?

As far as I can tell, I have nothing to main bond, which means all my
main bonding is in place. The electrician disagrees. He thinks that as
I have no bonding, it is not in place. He also wants to bond the
short length of copper pipe attached to the plastic water supply for
some reason.

The electrician says his mate who is going to "Part P" the work for
him insists on all the bonding. So who's right - the sparky or me?

If your electrician can't certify the work himself then he's not
a member of a competent persons scheme which makes one wonder how he
operates as a professional electrician, if that's what he calls himself.
Sounds as if you need to be talking to the mate of his who's actually
going to be certifying the work.

There does seem to be a breed of electricians who bond everything that
doesn't move. Attempting to bond what is practically an all-plastics water
supply does seem ludicrous, though probably to the letter of the law, and
I'd expect a sensible sparks to omit it with perhaps a note on the
deviations section of the installation certificate.

It seems that whether or not main bonding is regarded as being in
place has implications for supplementary bonding. Due to the
configuration of the bathrooms, I think the easiest and most sensible
way to supplementary bond in my situation is to run a cable from the
towel rails to the consumer unit, letting the CPCs do the rest. In
fact I don't think even that is necessary (bathrooms are on RCBOs),
but don't mind a bit of belt and braces. I don't see the point in
doing any more, but the electrician seems to want to put a lot more
in!

As for supplementary bonding that doesn't need to be taken to the main
earthing point: it just needs to connect extraneous conductive metalwork
in the special location and the cpcs of all electrical services entering
the location.

If all your pipework in the special location is plastic then you can make
it an earth-free rather than equipotentially-bonded zone: this is regarded
by the IET as preferable.



--
John Stumbles -- http://yaph.co.uk

militant pacifist

wrote in message
...
I don't have any metal pipework coming into my house. The water supply
is plastic - followed by a short length of copper, then speedfit. All
waste pipes are plastic. The only metallic object that could
conceivably be in contact with "earth" is my stove (which does my
central heating) .........


The electrician says his mate who is going to "Part P" the work for
him insists on all the bonding. So who's right - the sparky or me?

Probably you are right. The problem with many electricians is they want a
proforma way of tackling problems. They do not have the training as
engineers to understand what the regulations are trying to achieve and why.

Two points:
- The OSG on page 27 lists *metal central heating and air conditioning
systems* as candidates for main protective bonding if they are extraneous.
Note they may be extraneous because they are in contact with enough of a
damp building they they can introduce a potential. Normally only applies in
old houses.
- There is a test he can do to identify whether a part is extraneous and
that is to measure its resistance to earth (the MET). My recollection is 23
kOhms. This factsheet from ECA gives a value of 25 k Ohms
http://www.cila.co.uk/files/ECA%20Ma...ctsheet_05.pdf
So ask him to test whether it is extraneous.

Be impressed if you electrician does already know and understand what is in
that fact sheet. Many just take the proforma bond everything option.

Regards
Bruce

coughed up some electrons that declared:

I don't have any metal pipework coming into my house. The water supply
is plastic - followed by a short length of copper, then speedfit. All
waste pipes are plastic. The only metallic object that could
conceivably be in contact with "earth" is my stove (which does my
central heating) which is sat on the ground, arguably making the
bathroom towel rails extraneous conductive parts.

Hi

This covers some of the issues:

http://www.theiet.org/publishing/wir...s.cfm?type=pdf

(admittedly pre-17th Edition - but the spirit is similar - supplimentary
bonding was changed a bit in the 17th)

As far as I can tell, I have nothing to main bond, which means all my
main bonding is in place. The electrician disagrees. He thinks that as
I have no bonding, it is not in place. He also wants to bond the
short length of copper pipe attached to the plastic water supply for
some reason.

The On-Site Guide,17th says on page 29:

"There is no requirement to main bond an incoming service where the incoming
service pipe and the pipework within the installation are both plastic.
Where there is a plastic incoming service and a metal installation within
the premises, main bonding is recommended unless it has been confirmed that
any metal pipework within the building is not introducing an earth
potential. ..."

So that is the question that should be asked of the copper pipe.

The usual test for that is:

1) Run a flying wire back to the MET (main earth terminal) and have a Megger
or similar tester at the ready;

2) Test on low voltage continuity range between the wire to the MET and the
exposed metalwork in question. If the reading is off scale (high ohms),
then repeat the test with the 500V insulation test range.

3) If the reading from (2) is 23k Ohms, then the metal is an extraneous
conductive part, capable of introducing an earth potential into the room -
so bond.

[http://www.voltimum.co.uk/consult.ph...dex.questions]

You could do a rough test with a multimeter, but the final test is best done
with a proper test instrument.

It seems that whether or not main bonding is regarded as being in
place has implications for supplementary bonding. Due to the
configuration of the bathrooms, I think the easiest and most sensible
way to supplementary bond in my situation is to run a cable from the
towel rails to the consumer unit, letting the CPCs do the rest. In
fact I don't think even that is necessary (bathrooms are on RCBOs),
but don't mind a bit of belt and braces. I don't see the point in
doing any more, but the electrician seems to want to put a lot more
in!

The electrician says his mate who is going to "Part P" the work for
him insists on all the bonding. So who's right - the sparky or me?

Has his "mate" seen the installation? If not, it would be hard for him to
have an informed opinion as whether to bond depends on what's there.

Cheers

Tim

wrote:
I don't have any metal pipework coming into my house. The water supply
is plastic - followed by a short length of copper, then speedfit. All
waste pipes are plastic.

No water main bonding is required then - see page 29 of the OSG (red
17th ed. version). Clearly there's no point whatever in bonding the
short metal section, provided it is to remain short and electrically
floating. Metal gas or oil pipework in the premises might need main
bonding, but you haven't mentioned any.

The only metallic object that could conceivably be in contact with
"earth" is my stove (which does my central heating) which is sat on
the ground, arguably making the bathroom towel rails extraneous
conductive parts.

Where is this stove - outside? If it's in contact with the ground
(soil or damp concrete, etc.) then any metal pipework from it which
enters the house will need main bonding at or near the point(s) of entry.

As far as I can tell, I have nothing to main bond, which means all my
main bonding is in place. The electrician disagrees. He thinks that as
I have no bonding, it is not in place.

If none is required then the main bonding requirements are satisfied and
bathroom supplementary bonding can be omitted, provided all bathroom
circuits are RCD protected.

He also wants to bond the short length of copper pipe attached to the
plastic water supply for some reason.

Well it would do no harm, and covers his back if additional metalwork is
teed-in in the future.

It seems that whether or not main bonding is regarded as being in
place has implications for supplementary bonding. Due to the
configuration of the bathrooms, I think the easiest and most sensible
way to supplementary bond in my situation is to run a cable from the
towel rails to the consumer unit, letting the CPCs do the rest.

No, that would constitute main bonding and should be applied near the
point of entry of anything which might import an external earth
potential. Any supplementary bonding which may be required is purely
local (although it will be connected to the MET via the CPC(s) of any
circuit(s) whose exposed-conductive-parts are included in the bonding.

In fact I don't think even that is necessary (bathrooms are on
RCBOs), but don't mind a bit of belt and braces.

From what you've said, bathroom supplementary bonding would appear to
be unnecessary (but see above re possible need for main bonding incoming
metal pipes from an external stove). Page 31 in the OSG refers.

I don't see the point in doing any more, but the electrician seems to
want to put a lot more in!

How unusual :~)

--
Andy

Tim S coughed up some electrons that declared:


3) If the reading from (2) is 23k Ohms, then the metal is an extraneous
^^^ LESS THAN 23k
conductive part, capable of introducing an earth potential into the room -
so bond.

I read this over once - must refrain from posting before coffee worked...

On 9 Apr, 08:30, YAPH wrote:

Are you all electric then? No gas or oil?


Just electricity and wood I'm afraid...


As for supplementary bonding that doesn't need to be taken to the main
earthing point: it just needs to connect extraneous conductive metalwork
in the special location and the cpcs of all electrical services entering
the location.


It just so happens that the CU is a convenient place to connect the
supplementary bonding to the CPCs. The central heating is in copper
and comes up from below. A 4mm wire can easily be run under the floor
from the towel rail to the CU. All the electricity enters the
bathrooms from above, making bonding less convenient. Is connecting at
the CU OK?


If all your pipework in the special location is plastic then you can make
it an earth-free rather than equipotentially-bonded zone: this is regarded
by the IET as preferable.


The central heating is copper, so the towel rail is probably
"extraneous". The trouble is, the electrician is of the opinion that
as there is no bonding, supplementary bonding is required even though
the bathrooms are on RCBOs (as is everything). I think that all
bonding that should be in place is in place (ie none), so
supplementary bonding is not required.