Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined
protective earth and neutral to save money aka PEN and TN-C-S. This
seems to be permitted in BS 7671 although I have never seen it myself.

https://en.wikipedia.org/wiki/Earthi...of_TN_networks

All the installations I have ever seen are either rural TT or old build
TN-S where the sheath of the incoming armoured cable is a true earth.

So how common is TN-C-S with a single PEN in new build? What proportion
of homes in the UK have the potential for every metallic "earth" bonded
surface in them to be made live if the neutral return were to fail?
(It only requires one appliance to be on for this to happen)

The best description of it I have found so far is he

https://professional-electrician.com...earthings-pme/

So it seems some UK households do have this configuration.

--
Regards,
Martin Brown

Have we not had this conversation quite recently?
Interestingly enough, our council put out a press release this morning
about enabling people to get charging points that were good enough at home
and of course on the street operated by mobile tech, apparently.
All well and good but surely they must also realise that all of this puts
up demand for power in a climate of lack of investment in Nuclear, the only
current viable way to generate it without either greenhouse gasses being
emitted or the high cost and intermittent nature of renewables.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Martin Brown" wrote in message
...

Arising from the EV Charging in the UK thread I am having an argument with
a USian who insists that UK wiring is unsafe and uses a combined
protective earth and neutral to save money aka PEN and TN-C-S. This seems
to be permitted in BS 7671 although I have never seen it myself.

https://en.wikipedia.org/wiki/Earthi...of_TN_networks

All the installations I have ever seen are either rural TT or old build
TN-S where the sheath of the incoming armoured cable is a true earth.

So how common is TN-C-S with a single PEN in new build? What proportion of
homes in the UK have the potential for every metallic "earth" bonded
surface in them to be made live if the neutral return were to fail?
(It only requires one appliance to be on for this to happen)

The best description of it I have found so far is he

https://professional-electrician.com...earthings-pme/

So it seems some UK households do have this configuration.

--
Regards,
Martin Brown

On 18/06/2019 09:13, Martin Brown wrote:

Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined
protective earth and neutral to save money aka PEN and TN-C-S. This
seems to be permitted in BS 7671 although I have never seen it myself.

https://en.wikipedia.org/wiki/Earthi...of_TN_networks

All the installations I have ever seen are either rural TT or old build
TN-S where the sheath of the incoming armoured cable is a true earth.

So how common is TN-C-S with a single PEN in new build? What proportion
of homes in the UK have the potential for every metallic "earth" bonded
surface in them to be made live if the neutral return were to fail?
(It only requires one appliance to be on for this to happen)

The best description of it I have found so far is he

https://professional-electrician.com...earthings-pme/


So it seems some UK households do have this configuration.


AFAIK PME has been the /default/ for new, ordinary connections for quite
some time. (By 'ordinary' I mean not a caravan, boat, railway etc.)
And a fair few older houses which started out as TN-S have been switched
to PME.


--
Robin
reply-to address is (intended to be) valid

Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

AFAIK PME has been the /default/ for new, ordinary connections for quite
some time.

me too, with "quite some time" being from the late 60's onwards, except
overhead supplies?

On Tue, 18 Jun 2019 09:37:46 +0100, Brian Gaff wrote:

All well and good but surely they must also realise that all of this
puts up demand for power in a climate of lack of investment in Nuclear,
the only current viable way to generate it without either greenhouse
gasses being emitted or the high cost and intermittent nature of
renewables.

I doubt they realise at all. The general populus has been lulled into
a very deep sense of security due to the reliabilty of the Britain's
mains electricity. It's always there, it happens by "magic". They
haven't clue how much effort goes on in the background to keep the
lights on or the limitations of the whole system from generation to
local distribution. Even less idea of how much energy transport
consumes.

--
Cheers
Dave.

On 18/06/2019 09:13, Martin Brown wrote:

Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined

Its a little rich for someone in the US to complain that *our*
electrical systems are unsafe... You only need look at the electrocution
stats where they have annual death rates of thousands a year compared
with the "tens" per year we would expect here.

protective earth and neutral to save money aka PEN and TN-C-S. This
seems to be permitted in BS 7671 although I have never seen it myself.

https://en.wikipedia.org/wiki/Earthi...of_TN_networks

Its typically used on all new installs, and is the preferred method of
installation.

It also means that the supplier can provide an earth on overhead
supplies where previously that was not usually possible.

All the installations I have ever seen are either rural TT or old build
TN-S where the sheath of the incoming armoured cable is a true earth.

So how common is TN-C-S with a single PEN in new build? What proportion
of homes in the UK have the potential for every metallic "earth" bonded
surface in them to be made live if the neutral return were to fail?
(It only requires one appliance to be on for this to happen)

Its important to understand the roll and significance of PME in this
setup. We tend to use the terms PME and TN-C-S interchangeably, although
technically I suppose you could have TN-C-S without PME.

PME requires that the PEN conductor is earthed at *multiple* locations
all along the delivery path. So on overhead wiring it would be common to
earth it every few poles. (its also how some overhead supply systems can
be upgraded to support TN-C-S even if they did not initially do so. For
example, my setup here is overhead and TT, however the network was
upgraded latter with PME, so I could switch to TN-C-S if I wanted.

(it is also probably one of the reasons that Aerial Bundled
Conductors/Cables ("ABCs") are favoured for new overhead LV distribution
in the street - it make it much harder to snag and break the neutral in
isolation)

So while there is a risk associated with TN-C-S should the PEN be
interrupted[1], its considered a worthwhile trade off for the very good
low impedance earth provided, the ability to supply an earth connection
in most circumstances now, and the reduction of potential difference
between neutral and local earth at the property.



[1] and that is why the wiring regs, have specific requirements for
mitigating the risks of TN-C-S supplies.





--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

AFAIK PME has been the /default/ for new, ordinary connections for
quite some time.

me too, with "quite some time" being from the late 60's onwards, except
overhead supplies?

Overhead supplies have often had PME added later. This place (overhead
supply) was fully rewired in the mid 80's I believe, and was TT then.
However at some time in the 10 to 15 years after that, the network must
have been upgraded to PME since the cutout now sports a yellow PME label
(well spotted Adam!)



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Tue, 18 Jun 2019 12:58:50 +0100, John Rumm
wrote:

On 18/06/2019 09:13, Martin Brown wrote:

Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined

Its a little rich for someone in the US to complain that *our*
electrical systems are unsafe... You only need look at the electrocution
stats where they have annual death rates of thousands a year compared
with the "tens" per year we would expect here.

I heard that with 110V it is recognised practice to test for live
using one finger. Is this apocryphal?

On Tue, 18 Jun 2019 16:02:00 +0100, Scott wrote:

On Tue, 18 Jun 2019 12:58:50 +0100, John Rumm
wrote:

On 18/06/2019 09:13, Martin Brown wrote:

Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined

Its a little rich for someone in the US to complain that *our*
electrical systems are unsafe... You only need look at the electrocution
stats where they have annual death rates of thousands a year compared
with the "tens" per year we would expect here.

I heard that with 110V it is recognised practice to test for live
using one finger. Is this apocryphal?

Digital technology.


--
Regards, Paul Herber
http://www.paulherber.co.uk/

In article l.net,
Dave Liquorice wrote:
On Tue, 18 Jun 2019 09:37:46 +0100, Brian Gaff wrote:

All well and good but surely they must also realise that all of this
puts up demand for power in a climate of lack of investment in Nuclear,
the only current viable way to generate it without either greenhouse
gasses being emitted or the high cost and intermittent nature of
renewables.

I doubt they realise at all. The general populus has been lulled into
a very deep sense of security due to the reliabilty of the Britain's
mains electricity. It's always there, it happens by "magic". They
haven't clue how much effort goes on in the background to keep the
lights on or the limitations of the whole system from generation to
local distribution. Even less idea of how much energy transport
consumes.

I suspect the last time the general public were affected was whn a
Duisrtibution board in Battersea failed. That took out most of West London
- including BBC TV Centre. The reserved feed to that building was "fed
directly from Battersea" - from the power board that failed. The emergebncy
generator hadn't yet been commissioned so BBC2' first night didn't happen.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

charles wrote:

I suspect the last time the general public were affected was whn a
Duisrtibution board in Battersea failed. That took out most of West London

Didn't half of South London have to walk home on 28th August 2003?

On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.


I am also sure that I am not sure. New builds in Epworth that I have
just worked on (one street). Half are TN-C-S with a 100A supply and half
are TN-S with a 80A supply.

However I would say that 80% of newbuilds I have worked on in the last
20 years are supplied with a single core concentric cable.


--
Adam

On 18/06/2019 12:58, John Rumm wrote:
On 18/06/2019 09:13, Martin Brown wrote:

Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined

Its a little rich for someone in the US to complain that *our*
electrical systems are unsafe... You only need look at the electrocution
stats where they have annual death rates of thousands a year compared
with the "tens" per year we would expect here.

Because of their **** 110V supply with the hot wire and lots of
aluminium or because they have a lot of Homer Simpsons?


--
Adam

John Rumm wrote:

On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

AFAIK PME has been the /default/ for new, ordinary connections for
quite some time.

me too, with "quite some time" being from the late 60's onwards, except
overhead supplies?

Overhead supplies have often had PME added later. This place (overhead
supply) was fully rewired in the mid 80's I believe, and was TT then.
However at some time in the 10 to 15 years after that, the network must
have been upgraded to PME since the cutout now sports a yellow PME label
(well spotted Adam!)

What would be the reason for not using PME with overhead supplies in the
first place? Were some ot the neutral wires too long to have a low
enough resistance? Or was it just that most overhead supplies were put
in before PME was fashionable? Our overhead supply is PME but it was
redone in the 80s.


--

Roger Hayter

On Tuesday, 18 June 2019 09:13:28 UTC+1, Martin Brown wrote:
Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined
protective earth and neutral to save money aka PEN and TN-C-S. This
seems to be permitted in BS 7671 although I have never seen it myself.

https://en.wikipedia.org/wiki/Earthi...of_TN_networks

All the installations I have ever seen are either rural TT or old build
TN-S where the sheath of the incoming armoured cable is a true earth.

So how common is TN-C-S with a single PEN in new build? What proportion
of homes in the UK have the potential for every metallic "earth" bonded
surface in them to be made live if the neutral return were to fail?
(It only requires one appliance to be on for this to happen)

The best description of it I have found so far is he

https://professional-electrician.com...earthings-pme/

So it seems some UK households do have this configuration.

PME is used by supplier networks, others have already mentioned the 'multiple' bit. Combined N&E is not used within the house wiring itself - in America it has been in the past.


NT

On 18/06/2019 22:27, Roger Hayter wrote:
John Rumm wrote:

On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

AFAIK PME has been the /default/ for new, ordinary connections for
quite some time.

me too, with "quite some time" being from the late 60's onwards, except
overhead supplies?

Overhead supplies have often had PME added later. This place (overhead
supply) was fully rewired in the mid 80's I believe, and was TT then.
However at some time in the 10 to 15 years after that, the network must
have been upgraded to PME since the cutout now sports a yellow PME label
(well spotted Adam!)

What would be the reason for not using PME with overhead supplies in the
first place? Were some ot the neutral wires too long to have a low
enough resistance? Or was it just that most overhead supplies were put
in before PME was fashionable? Our overhead supply is PME but it was
redone in the 80s.

I would guess that the neutral was designed to be just that, and not a
PEN conductor, and it was only earthed only the once at the sub station
in the same way that a TN-S supply would be. Hence there would be a much
greater risk if the neutral was cut anywhere along the route.

As to why, perhaps because it is more expensive to PME an overhead
supply, or simply they did see the need at the time, and considered that
leaving it TT was ok.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 18/06/2019 16:02, Scott wrote:
On Tue, 18 Jun 2019 12:58:50 +0100, John Rumm
wrote:

On 18/06/2019 09:13, Martin Brown wrote:

Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined

Its a little rich for someone in the US to complain that *our*
electrical systems are unsafe... You only need look at the electrocution
stats where they have annual death rates of thousands a year compared
with the "tens" per year we would expect here.

I heard that with 110V it is recognised practice to test for live
using one finger. Is this apocryphal?

I am sure some do (I have known people who do that with 240), but I
can't see it being recommended practice!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 18/06/2019 16:02, Scott wrote:
On Tue, 18 Jun 2019 12:58:50 +0100, John Rumm
wrote:

On 18/06/2019 09:13, Martin Brown wrote:

Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined

Its a little rich for someone in the US to complain that *our*
electrical systems are unsafe... You only need look at the electrocution
stats where they have annual death rates of thousands a year compared
with the "tens" per year we would expect here

I heard that with 110V it is recognised practice to test for live
using one finger. Is this apocryphal?

No. I had to administer first aid to a US installation engineer being
trained at our facility in the UK who used that approach on UK mains. It
threw him across the room knocking the wind out of him entirely. After
the incident a warning was added to training materials never to do this!

Warm sweet tea aided his recovery but he was lucky not to be more
seriously hurt. One of my friends at university got hold of the wrong
end of a Jesus lead with serious very burns to his hand resulting.

--
Regards,
Martin Brown

On 18/06/2019 21:42, ARW wrote:
On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

I am also sure that I am not sure. New builds in Epworth that I have
just worked on (one street). Half are TN-C-S with a 100A supply and half
are TN-S with a 80A supply.

Thanks. You would think it made more sense to do one or the other.

However I would say that 80% of newbuilds I have worked on in the last
20 years are supplied with a single core concentric cable.

So the incoming armoured cable has a live core and outer PEN sheath?

I expect it is against the wiring code but is there anything to prevent
the householder having a stake in the ground bonded to the household
protective earth in addition? It won't make a blind bit of difference
most of the time but if the neutral return ever fails then at least you
don't suddenly find every household appliance is live to the touch.

It is just after all another parallel multiple earth local to the
premises and although it cannot sink anything like the current that the
PEN can it does have the advantage of keeping the water pipes from
becoming live in the unlikely event of a fault.

Round here single phase or neutral return fail faults are not at all
uncommon if a tree branch hits a line as it falls. Usually the people on
the phase at the top of four wires bear the brunt of such cuts. The
first wire snapping slows the branch down enough that the second or
third one down survives.

Interestingly the new fully insulated steel cored combined aluminium
cable can survive a whole tree falling on it sometimes although it bent
all the poles and ripped several mains supplies off houses along one
side of the road. You get some interesting mains faults in rural areas.

Last big one was when the milk tanker skidded on ice on the coldest day
of the year and took out a pole wrecking all mains and phones.

--
Regards,
Martin Brown

On Tue, 18 Jun 2019 17:08:19 +0100, Andy Burns wrote:

I suspect the last time the general public were affected was whn a
Duisrtibution board in Battersea failed. That took out most of
West
London

Didn't half of South London have to walk home on 28th August 2003?

The Sizewell/Longannet incident of May 2008 is likely to have
affected the power to far more people than either of those. The
automatics dropped customers off supply across London, Cheshire,
Merseyside and East Anglia.

I expect the whole country felt the effects of it as well. We didn't
lose power but had a big dip and unstable supply for a few seconds.

--
Cheers
Dave.

On 19/06/2019 09:17, Martin Brown wrote:
On 18/06/2019 21:42, ARW wrote:
On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

I am also sure that I am not sure. New builds in Epworth that I have
just worked on (one street). Half are TN-C-S with a 100A supply and
half are TN-S with a 80A supply.

Thanks. You would think it made more sense to do one or the other.

However I would say that 80% of newbuilds I have worked on in the last
20 years are supplied with a single core concentric cable.

So the incoming armoured cable has a live core and outer PEN sheath?

I expect it is against the wiring code but is there anything to prevent
the householder having a stake in the ground bonded to the household
protective earth in addition? It won't make a blind bit of difference
most of the time but if the neutral return ever fails then at least you
don't suddenly find every household appliance is live to the touch.

You can have an earth stake with a PME supply - it just becomes another
of the multiple earths.

(There was even a suggestion that the 18th edition might make it a
requirement - but that was shelved when they thought through the
impracticalities of that in a number of circumstances)

It is just after all another parallel multiple earth local to the
premises and although it cannot sink anything like the current that the
PEN can it does have the advantage of keeping the water pipes from
becoming live in the unlikely event of a fault.

For some values of live. Its one of the reasons TN-C-S installs are so
insistent on the need for maintaining an equipotential zone. The theory
being that live water pipes etc are only a risk if you are able to touch
them and something else that is at a true earth potential. If everything
you can touch is at much the same potential (even if that is 240V adrift
from true earth) there is no shock risk.

Round here single phase or neutral return fail faults are not at all
uncommon if a tree branch hits a line as it falls. Usually the people on
the phase at the top of four wires bear the brunt of such cuts. The
first wire snapping slows the branch down enough that the second or
third one down survives.

Interestingly the new fully insulated steel cored combined aluminium
cable can survive a whole tree falling on it sometimes although it bent
all the poles and ripped several mains supplies off houses along one
side of the road. You get some interesting mains faults in rural areas.

Yup, ABCs are more robust in general, and its also much harder to snap
just one of the conductors.


Last big one was when the milk tanker skidded on ice on the coldest day
of the year and took out a pole wrecking all mains and phones.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:

On 18/06/2019 22:27, Roger Hayter wrote:
John Rumm wrote:

On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

AFAIK PME has been the /default/ for new, ordinary connections for
quite some time.

me too, with "quite some time" being from the late 60's onwards, except
overhead supplies?

Overhead supplies have often had PME added later. This place (overhead
supply) was fully rewired in the mid 80's I believe, and was TT then.
However at some time in the 10 to 15 years after that, the network must
have been upgraded to PME since the cutout now sports a yellow PME label
(well spotted Adam!)

What would be the reason for not using PME with overhead supplies in the
first place? Were some ot the neutral wires too long to have a low
enough resistance? Or was it just that most overhead supplies were put
in before PME was fashionable? Our overhead supply is PME but it was
redone in the 80s.

I would guess that the neutral was designed to be just that, and not a
PEN conductor, and it was only earthed only the once at the sub station
in the same way that a TN-S supply would be. Hence there would be a much
greater risk if the neutral was cut anywhere along the route.

As to why, perhaps because it is more expensive to PME an overhead
supply, or simply they did see the need at the time, and considered that
leaving it TT was ok.

Thanks. I will look more at our local supply and see if I can work out
where they have put earths. Only 3 poles and five houses.

--

Roger Hayter

On 19/06/2019 10:49, Roger Hayter wrote:
John Rumm wrote:

On 18/06/2019 22:27, Roger Hayter wrote:
John Rumm wrote:

On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

AFAIK PME has been the /default/ for new, ordinary connections for
quite some time.

me too, with "quite some time" being from the late 60's onwards, except
overhead supplies?

Overhead supplies have often had PME added later. This place (overhead
supply) was fully rewired in the mid 80's I believe, and was TT then.
However at some time in the 10 to 15 years after that, the network must
have been upgraded to PME since the cutout now sports a yellow PME label
(well spotted Adam!)

What would be the reason for not using PME with overhead supplies in the
first place? Were some ot the neutral wires too long to have a low
enough resistance? Or was it just that most overhead supplies were put
in before PME was fashionable? Our overhead supply is PME but it was
redone in the 80s.

I would guess that the neutral was designed to be just that, and not a
PEN conductor, and it was only earthed only the once at the sub station
in the same way that a TN-S supply would be. Hence there would be a much
greater risk if the neutral was cut anywhere along the route.

As to why, perhaps because it is more expensive to PME an overhead
supply, or simply they did see the need at the time, and considered that
leaving it TT was ok.

Thanks. I will look more at our local supply and see if I can work out
where they have put earths. Only 3 poles and five houses.

Yup, that's a good point actually - We have a pole mounted transformer
feeding a dozen or so properties. Must admit I have never studied the
earthing closely. They replaced our 4 line street wiring a couple of
years ago with ABC.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Martin Brown wrote:

On 18/06/2019 21:42, ARW wrote:
On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

I am also sure that I am not sure. New builds in Epworth that I have
just worked on (one street). Half are TN-C-S with a 100A supply and half
are TN-S with a 80A supply.

Thanks. You would think it made more sense to do one or the other.

However I would say that 80% of newbuilds I have worked on in the last
20 years are supplied with a single core concentric cable.

So the incoming armoured cable has a live core and outer PEN sheath?

I expect it is against the wiring code but is there anything to prevent
the householder having a stake in the ground bonded to the household
protective earth in addition? It won't make a blind bit of difference
most of the time but if the neutral return ever fails then at least you
don't suddenly find every household appliance is live to the touch.

A simple earth stake can't do any harm, but it is not necessarily going
to make that much difference to the potential reached during a neutral
fault. Say the active loads on the supply beyond the fault add up to
about 5kW, resistance 12 ohms. And the best likely stake gives 100 ohms
earth resistance. Then it is only going to reduce the final voltage on
the house earth by about ten percent.

--

Roger Hayter

John Rumm wrote:

On 19/06/2019 10:49, Roger Hayter wrote:
John Rumm wrote:

On 18/06/2019 22:27, Roger Hayter wrote:
John Rumm wrote:

On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

AFAIK PME has been the /default/ for new, ordinary connections for
quite some time.

me too, with "quite some time" being from the late 60's onwards, except
overhead supplies?

Overhead supplies have often had PME added later. This place (overhead
supply) was fully rewired in the mid 80's I believe, and was TT then.
However at some time in the 10 to 15 years after that, the network must
have been upgraded to PME since the cutout now sports a yellow PME label
(well spotted Adam!)

What would be the reason for not using PME with overhead supplies in the
first place? Were some ot the neutral wires too long to have a low
enough resistance? Or was it just that most overhead supplies were put
in before PME was fashionable? Our overhead supply is PME but it was
redone in the 80s.

I would guess that the neutral was designed to be just that, and not a
PEN conductor, and it was only earthed only the once at the sub station
in the same way that a TN-S supply would be. Hence there would be a much
greater risk if the neutral was cut anywhere along the route.

As to why, perhaps because it is more expensive to PME an overhead
supply, or simply they did see the need at the time, and considered that
leaving it TT was ok.

Thanks. I will look more at our local supply and see if I can work out
where they have put earths. Only 3 poles and five houses.

Yup, that's a good point actually - We have a pole mounted transformer
feeding a dozen or so properties. Must admit I have never studied the
earthing closely. They replaced our 4 line street wiring a couple of
years ago with ABC.

They recently changed our single phase transformer, and used new ABC
cables from the tansformer pole. But the two houses that have two wire
overhead connections from a second pole got left untouched. We have a
TN-C-S supply, but I don't know about the other four houses. Ours and a
newly supplied building have underground connections to a nearby pole
supply which I suppose provided another earthing opportunity, but I
don't know if they used it.





--

Roger Hayter

On 19/06/2019 11:25, Roger Hayter wrote:
Martin Brown wrote:

On 18/06/2019 21:42, ARW wrote:
On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

I am also sure that I am not sure. New builds in Epworth that I have
just worked on (one street). Half are TN-C-S with a 100A supply and half
are TN-S with a 80A supply.

Thanks. You would think it made more sense to do one or the other.

However I would say that 80% of newbuilds I have worked on in the last
20 years are supplied with a single core concentric cable.

So the incoming armoured cable has a live core and outer PEN sheath?

I expect it is against the wiring code but is there anything to prevent
the householder having a stake in the ground bonded to the household
protective earth in addition? It won't make a blind bit of difference
most of the time but if the neutral return ever fails then at least you
don't suddenly find every household appliance is live to the touch.

A simple earth stake can't do any harm, but it is not necessarily going
to make that much difference to the potential reached during a neutral
fault. Say the active loads on the supply beyond the fault add up to
about 5kW, resistance 12 ohms. And the best likely stake gives 100 ohms
earth resistance. Then it is only going to reduce the final voltage on
the house earth by about ten percent.

Much will depend on the soil conditions for the stake. Last time I
measured mine[1] it was around 6 - 7 ohms.

[1] Into clay soil, and measured with a high current loop tester rather
than one of the modern "non trip" types.


--
Cheers,

John.

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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:

On 19/06/2019 11:25, Roger Hayter wrote:
Martin Brown wrote:

On 18/06/2019 21:42, ARW wrote:
On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

I am also sure that I am not sure. New builds in Epworth that I have
just worked on (one street). Half are TN-C-S with a 100A supply and half
are TN-S with a 80A supply.

Thanks. You would think it made more sense to do one or the other.

However I would say that 80% of newbuilds I have worked on in the last
20 years are supplied with a single core concentric cable.

So the incoming armoured cable has a live core and outer PEN sheath?

I expect it is against the wiring code but is there anything to prevent
the householder having a stake in the ground bonded to the household
protective earth in addition? It won't make a blind bit of difference
most of the time but if the neutral return ever fails then at least you
don't suddenly find every household appliance is live to the touch.

A simple earth stake can't do any harm, but it is not necessarily going
to make that much difference to the potential reached during a neutral
fault. Say the active loads on the supply beyond the fault add up to
about 5kW, resistance 12 ohms. And the best likely stake gives 100 ohms
earth resistance. Then it is only going to reduce the final voltage on
the house earth by about ten percent.

Much will depend on the soil conditions for the stake. Last time I
measured mine[1] it was around 6 - 7 ohms.

[1] Into clay soil, and measured with a high current loop tester rather
than one of the modern "non trip" types.

That's impressive. Does the clay stay wet all year round?

--

Roger Hayter

On 19/06/2019 23:34, Roger Hayter wrote:
John Rumm wrote:

On 19/06/2019 11:25, Roger Hayter wrote:
Martin Brown wrote:

On 18/06/2019 21:42, ARW wrote:
On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

I am also sure that I am not sure. New builds in Epworth that I have
just worked on (one street). Half are TN-C-S with a 100A supply and half
are TN-S with a 80A supply.

Thanks. You would think it made more sense to do one or the other.

However I would say that 80% of newbuilds I have worked on in the last
20 years are supplied with a single core concentric cable.

So the incoming armoured cable has a live core and outer PEN sheath?

I expect it is against the wiring code but is there anything to prevent
the householder having a stake in the ground bonded to the household
protective earth in addition? It won't make a blind bit of difference
most of the time but if the neutral return ever fails then at least you
don't suddenly find every household appliance is live to the touch.

A simple earth stake can't do any harm, but it is not necessarily going
to make that much difference to the potential reached during a neutral
fault. Say the active loads on the supply beyond the fault add up to
about 5kW, resistance 12 ohms. And the best likely stake gives 100 ohms
earth resistance. Then it is only going to reduce the final voltage on
the house earth by about ten percent.

Much will depend on the soil conditions for the stake. Last time I
measured mine[1] it was around 6 - 7 ohms.

[1] Into clay soil, and measured with a high current loop tester rather
than one of the modern "non trip" types.

That's impressive. Does the clay stay wet all year round?

Once you are down a foot or so, yup seems to.

The top layer can dry out and shrink quite dramatically though. At the
end of the summer can can dump 15,000l of swimming pool water on the
lawn and it does not even leave a puddle!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article , Martin Brown '''newspam'''@ne
zumi.demon.co.uk scribeth thus
On 18/06/2019 16:02, Scott wrote:
On Tue, 18 Jun 2019 12:58:50 +0100, John Rumm
wrote:

On 18/06/2019 09:13, Martin Brown wrote:

Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined

Its a little rich for someone in the US to complain that *our*
electrical systems are unsafe... You only need look at the electrocution
stats where they have annual death rates of thousands a year compared
with the "tens" per year we would expect here

I heard that with 110V it is recognised practice to test for live
using one finger. Is this apocryphal?

No. I had to administer first aid to a US installation engineer being
trained at our facility in the UK who used that approach on UK mains. It
threw him across the room knocking the wind out of him entirely. After
the incident a warning was added to training materials never to do this!

Warm sweet tea aided his recovery but he was lucky not to be more
seriously hurt. One of my friends at university got hold of the wrong
end of a Jesus lead with serious very burns to his hand resulting.


Do you know many years ago now i used to work in a TV repair shop and we
used the Philips monochromes chassis which were notorious for blowing
mains dropper resistors the repair was to solder a large wire wound
resistor across the open circuit sections. We use to wrap it round with
pliers then solder it with a large instant heat gun, this was often just
had its wires to where the mains came into the TV.

Back then the TV chassis was likely to be at live mains potential on
the TV course back in two pin plug days and reversible connectors it was
quite often the done thing to have the whole metal chassis live.

No one ever got a bad belt but a tingle plugging up the aerial
sometimes;!..

--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

On 19/06/2019 10:45, John Rumm wrote:
On 19/06/2019 09:17, Martin Brown wrote:
On 18/06/2019 21:42, ARW wrote:
[snip]
It is just after all another parallel multiple earth local to the
premises and although it cannot sink anything like the current that
the PEN can it does have the advantage of keeping the water pipes from
becoming live in the unlikely event of a fault.

For some values of live. Its one of the reasons TN-C-S installs are so
insistent on the need for maintaining an equipotential zone. The theory
being that live water pipes etc are only a risk if you are able to touch
them and something else that is at a true earth potential. If everything
you can touch is at much the same potential (even if that is 240V adrift
from true earth) there is no shock risk.

Probably not a lethal shock but enough to be unpleasant.

I wouldn't trust my flagstone floor to be at anything other than local
ground potential. And I have had a small shock from a telescope that had
mains live leakage despite being up a wooden ladder at the time.

Round here single phase or neutral return fail faults are not at all
uncommon if a tree branch hits a line as it falls. Usually the people
on the phase at the top of four wires bear the brunt of such cuts. The
first wire snapping slows the branch down enough that the second or
third one down survives.

Interestingly the new fully insulated steel cored combined aluminium
cable can survive a whole tree falling on it sometimes although it
bent all the poles and ripped several mains supplies off houses along
one side of the road. You get some interesting mains faults in rural
areas.

Yup, ABCs are more robust in general, and its also much harder to snap
just one of the conductors.

Careful examination of the poles shows that they are now PME even if all
the houses round here all have a copper stake driven into the ground
from the original TT install where there were four independent wires any
one of which could be snapped independently (although usually it was the
top wire that got snapped moving neutral toward the remaining phases).

It was particularly exciting in wet weather with the remains of the
perished rubberised fabric hanging down and flapping in the breeze
arcing and sparking as it touched other conductors.

--
Regards,
Martin Brown

On 19/06/2019 23:50, John Rumm wrote:
On 19/06/2019 23:34, Roger Hayter wrote:
John Rumm wrote:

On 19/06/2019 11:25, Roger Hayter wrote:
Martin Brown wrote:

On 18/06/2019 21:42, ARW wrote:
On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here
combined.
I am also sure that I am not sure. New builds in Epworth that I have
just worked on (one street). Half are TN-C-S with a 100A supply
and half
are TN-S with a 80A supply.

Thanks. You would think it made more sense to do one or the other.

However I would say that 80% of newbuilds I have worked on in the
last
20 years are supplied with a single core concentric cable.

So the incoming armoured cable has a live core and outer PEN sheath?

I expect it is against the wiring code but is there anything to
prevent
the householder having a stake in the ground bonded to the household
protective earth in addition? It won't make a blind bit of difference
most of the time but if the neutral return ever fails then at least
you
don't suddenly find every household appliance is live to the touch.

A simple earth stake can't do any harm, but it is not necessarily going
to make that much difference to the potential reached during a neutral
fault.Â* Say the active loads on the supply beyond the fault add up to
about 5kW, resistance 12 ohms.Â* And the best likely stake gives 100
ohms
earth resistance.Â*Â* Then it is only going to reduce the final
voltage on
the house earth by about ten percent.

Much will depend on the soil conditions for the stake. Last time I
measured mine[1] it was around 6 - 7 ohms.

[1] Into clay soil, and measured with a high current loop tester rather
than one of the modern "non trip" types.

That's impressive.Â*Â* Does the clay stay wet all year round?

Once you are down a foot or so, yup seems to.

Same here. We have a very high water table and an intermittent spring
part way down the garden. I have to syphon water out of the pit before
using it. There is a capped well only a few metres away.

The top layer can dry out and shrink quite dramatically though. At the
end of the summer can can dump 15,000l of swimming pool water on the
lawn and it does not even leave a puddle!

The clay round here bakes to impermeable in a good summer which can mean
a big thunderstorm runs off the fields towards a couple of unlucky
houses. It doesn't happen very often but when it does the field drains
simply cannot keep up and we get a fountain at the bottom of our drive.

--
Regards,
Martin Brown

John Rumm wrote:
Its a little rich for someone in the US to complain that *our*
electrical systems are unsafe...

Anybody who wires up mains leccy with toothpaste tube caps, and
whose plugs are just modern versions of two nails hammered
through a lump of wood, has no right to complain about other
people's electrical systems. !

jgh

On Tuesday, 25 June 2019 05:16:22 UTC+1, wrote:
John Rumm wrote:

Its a little rich for someone in the US to complain that *our*
electrical systems are unsafe...

Anybody who wires up mains leccy with toothpaste tube caps, and
whose plugs are just modern versions of two nails hammered
through a lump of wood, has no right to complain about other
people's electrical systems. !

jgh

too funny. In fairness though, their domestic electrical fire rate is about the same per capita as ours. So it seems dognuts aren't as terrible as I thought.


NT

On 29/06/2019 01:32, Jim Michaels wrote:
On Tue, 18 Jun 2019 16:02:00 +0100, Scott
wrote:

On Tue, 18 Jun 2019 12:58:50 +0100, John Rumm
wrote:

On 18/06/2019 09:13, Martin Brown wrote:

Arising from the EV Charging in the UK thread I am having an argument
with a USian who insists that UK wiring is unsafe and uses a combined

Its a little rich for someone in the US to complain that *our*
electrical systems are unsafe... You only need look at the electrocution
stats where they have annual death rates of thousands a year compared
with the "tens" per year we would expect here.

I heard that with 110V it is recognised practice to test for live
using one finger. Is this apocryphal?

---
Unless Statistics are gathered using the same criteria, comparison can
lead to false ideas.

Of course...

Of the 1,000 US Electrical deaths per year about 300 are lightning
strikes, 400 are contact with high voltage power lines, and most of
the rest are trade workers doing something wrong.

Its rare to have any deaths at all from lightening here. Deaths from
contact with the HV network are also pretty rare (in years when one
occurs it typically makes the news. e.g.
https://metro.co.uk/2017/11/21/man-e...lines-7097446/

However if your figures are correct that still leaves 300 or so deaths -
more than ten times the number we would expect here, with a population
only five times the size.

Several sites indicate the UK has more than a few electrical saftey
concerns.
https://www.electricalsafetyfirst.or...stics-england/

Indeed, no system is perfect. However you need to read the stats
carefully. Many of the fires that are classed as "electrical" tend to
include things where the fire started due to misuse of an appliance like
an electric cooker - but there was no electrical fault - it was just the
source of ignition.

Of those where there was an electrical fault, its often something like a
fridge freezer or a tumble drier that was faulty and started a fire.
(the cause of the fire in the Grenfell disaster)

(Our electrocution death rate of the 20 - 30 / year includes deaths from
contact with fixed wiring (a handful a year) and also ones from
(mis)users of appliances.

Having said that the death rate is far from the whole storey - we will
have 100K plus hospital admissions per year for electrical injuries, and
a few 1000 of those will be more serious.

(also worth noting that electricalsafetyfirst is branch of one of the
electrical contracting trade associations - and they do have a habit of
"bigging up" their stats at times, and lobbying for more regulation etc)


Being a North American, I would have to use my passport to get
somewhere with 110V as normal wiring ( a British shaver outlet comes
to mind )

They have isolating transformers included, so you would be fine so long
as you don't touch both poles at once!



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:
On 18/06/2019 10:01, Andy Burns wrote:
Robin wrote:

Martin Brown wrote:

So how common is TN-C-S with a single PEN in new build?

I'm sure Adam can add more datapoints than everyone else here combined.

AFAIK PME has been the /default/ for new, ordinary connections for
quite some time.

me too, with "quite some time" being from the late 60's onwards, except
overhead supplies?

Overhead supplies have often had PME added later. This place (overhead
supply) was fully rewired in the mid 80's I believe, and was TT then.
However at some time in the 10 to 15 years after that, the network must
have been upgraded to PME since the cutout now sports a yellow PME label
(well spotted Adam!)




We have an o/h supply to a house built in the mid 80s and have PME.



--
Corbyn & the EU, the Nazis next step: "Our aim was Europe a nation. Our
faith European Socialism" Mosley "My Life" autobiography 1957.

On 29/06/2019 03:25, John Rumm wrote:
However if your figures are correct that still leaves 300 or so deaths -
more than ten times the number we would expect here, with a population
only five times the size.
? IIRC the USA is ten times the population of the UK



--
"The great thing about Glasgow is that if there's a nuclear attack it'll
look exactly the same afterwards."

Billy Connolly

"The Natural Philosopher" wrote in message
...
On 29/06/2019 03:25, John Rumm wrote:
However if your figures are correct that still leaves 300 or so deaths -
more than ten times the number we would expect here, with a population
only five times the size.
? IIRC the USA is ten times the population of the UK

Fraid not. 327m and 67m

On 29/06/2019 07:13, Levi Jones wrote:


"The Natural Philosopher" wrote in message
...
On 29/06/2019 03:25, John Rumm wrote:
However if your figures are correct that still leaves 300 or so
deaths - more than ten times the number we would expect here, with a
population only five times the size.
? IIRC the USA is ten times the population of the UK

Fraid not. 327m and 67m

Thought usa was 670m?

Ah that is NORTH AMERICA with canada mexico Cuba etc thrown in...



--
"The great thing about Glasgow is that if there's a nuclear attack it'll
look exactly the same afterwards."

Billy Connolly

On Sat, 29 Jun 2019 16:13:52 +1000, Levi Jones, better known as cantankerous
trolling senile geezer Rodent Speed, wrote:


However if your figures are correct that still leaves 300 or so deaths -
more than ten times the number we would expect here, with a population
only five times the size.
? IIRC the USA is ten times the population of the UK

Fraid not. 327m and 67m

You looked it up, just to find out whether there's another opportunity for
you to contradict, senile idiot? LOL

--
Sqwertz to Rot Speed:
"This is just a hunch, but I'm betting you're kinda an argumentative
asshole.
MID:

On Saturday, 29 June 2019 03:25:32 UTC+1, John Rumm wrote:
On 29/06/2019 01:32, Jim Michaels wrote:

Several sites indicate the UK has more than a few electrical saftey
concerns.
https://www.electricalsafetyfirst.or...stics-england/

7734 fires from white goods
241 from dishwashers
214 from refrigeration.
So where do the other 7000 come from?


NT