"John Rumm" wrote in message
o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a radial
circuit. Hence there are two paths to earth - and both connections would
have to fail to lose the earth at the socket. A complete failure at one
socket would not affect the earthing of the others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a radial
without the ring at the first fault and the user will never know.
In fact unless its tested you may never have the ring and the user wouldn't
be able to tell.

It really is a problem designing systems with redundancy that actually work,
and is impossible if you can't tell a fault has occurred.

On Aug 23, 8:51*pm, "dennis@home"
wrote:
"John Rumm" wrote in message

o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a radial
circuit. Hence there are two paths to earth - and both connections would
have to fail to lose the earth at the socket. A complete failure at one
socket would not affect the earthing of the others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a radial
without the ring at the first fault and the user will never know.
In fact unless its tested you may never have the ring and the user wouldn't
be able to tell.

It really is a problem designing systems with redundancy that actually work,
and is impossible if you can't tell a fault has occurred.

If you dont understand anything, why comment

dennis@home wrote:
"John Rumm" wrote in message
o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a
radial circuit. Hence there are two paths to earth - and both
connections would have to fail to lose the earth at the socket. A
complete failure at one socket would not affect the earthing of the
others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a radial
without the ring at the first fault and the user will never know.
In fact unless its tested you may never have the ring and the user
wouldn't be able to tell.

Will degenerate? WTF are you on?


--
Adam

NT wrote:
On Aug 23, 8:51 pm, "dennis@home"
wrote:
"John Rumm" wrote in message

o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a
radial circuit. Hence there are two paths to earth - and both
connections would have to fail to lose the earth at the socket. A
complete failure at one socket would not affect the earthing of the
others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a
radial without the ring at the first fault and the user will never
know.
In fact unless its tested you may never have the ring and the user
wouldn't be able to tell.

It really is a problem designing systems with redundancy that
actually work, and is impossible if you can't tell a fault has
occurred.

If you dont understand anything, why comment

Lack of medication?

But don't worry, he will soon say that it was a spelling mistake and that
you are picking on him.

--
Adam

"NT" wrote in message
...
On Aug 23, 8:51 pm, "dennis@home"
wrote:
"John Rumm" wrote in message

o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a
radial
circuit. Hence there are two paths to earth - and both connections
would
have to fail to lose the earth at the socket. A complete failure at one
socket would not affect the earthing of the others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a radial
without the ring at the first fault and the user will never know.
In fact unless its tested you may never have the ring and the user
wouldn't
be able to tell.

It really is a problem designing systems with redundancy that actually
work,
and is impossible if you can't tell a fault has occurred.

If you dont understand anything, why comment

I take it you don't understand then.

On 23/08/2011 20:20, Dave Plowman (News) wrote:
In articleBemdnegRV7cjcc7TnZ2dnUVZ7sSdnZ2d@brightvie w.co.uk,
John wrote:
(As an aside, the wires should not be twisted).

Is the reason simply they may break - at some point in the future if not
at the time?

More a case of it making it harder to fault find later, plus a slight
increase in the chances that you will break a wire by work hardening it.


--
Cheers,

John.

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

On 23/08/2011 20:51, dennis@home wrote:


"John Rumm" wrote in message
o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a
radial circuit. Hence there are two paths to earth - and both
connections would have to fail to lose the earth at the socket. A
complete failure at one socket would not affect the earthing of the
others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a radial
without the ring at the first fault and the user will never know.

Which would be preferable to the alternate arrangement where it
degenerates into a section of a radial circuit being unearthed
altogether and the user not knowing.

In fact unless its tested you may never have the ring and the user
wouldn't be able to tell.

One would test just as one would for any other new circuit.

It really is a problem designing systems with redundancy that actually
work, and is impossible if you can't tell a fault has occurred.

It addresses a particular risk of circuits with high earth leakage - it
does not eliminate the risk completely - something that can never be
done. It does however reduce it for a marginal extra cost in materials
and effort. As with all engineering its a case of compromise.


--
Cheers,

John.

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

"John Rumm" wrote in message
o.uk...
On 23/08/2011 20:51, dennis@home wrote:


"John Rumm" wrote in message
o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a
radial circuit. Hence there are two paths to earth - and both
connections would have to fail to lose the earth at the socket. A
complete failure at one socket would not affect the earthing of the
others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a radial
without the ring at the first fault and the user will never know.

Which would be preferable to the alternate arrangement where it
degenerates into a section of a radial circuit being unearthed altogether
and the user not knowing.

In fact unless its tested you may never have the ring and the user
wouldn't be able to tell.

One would test just as one would for any other new circuit.

It really is a problem designing systems with redundancy that actually
work, and is impossible if you can't tell a fault has occurred.

It addresses a particular risk of circuits with high earth leakage - it
does not eliminate the risk completely - something that can never be done.
It does however reduce it for a marginal extra cost in materials and
effort. As with all engineering its a case of compromise.

its marginal at best..

suppose its a simple circuit.. one socket two wires between the socket and
the consumer unit.

that is twice as many joints terminated as a single wire circuit.
so there is twice the rate of failure.
So that means the dual circuit is not twice as reliable as the single
circuit and the first fault will in the dual circuit will (on average)occur
in half the time the first fault will occur on the single circuit. The
second will occur somewhere near the time the first would occur on the
single circuit (being as it has half the failure rate due to having half the
components).
This is true for any replicated system where the faults are undetected and
not fixed.

There are a load of equations that tell you how reliable a system is, but
they all assume you can detect the fault and hence repair it, which you
can't easily do in this case.

dennis@home wrote:
"John Rumm" wrote in message
o.uk...
On 23/08/2011 20:51, dennis@home wrote:


"John Rumm" wrote in message
o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a
radial circuit. Hence there are two paths to earth - and both
connections would have to fail to lose the earth at the socket. A
complete failure at one socket would not affect the earthing of the
others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a
radial without the ring at the first fault and the user will never
know.

Which would be preferable to the alternate arrangement where it
degenerates into a section of a radial circuit being unearthed
altogether and the user not knowing.

In fact unless its tested you may never have the ring and the user
wouldn't be able to tell.

One would test just as one would for any other new circuit.

It really is a problem designing systems with redundancy that
actually work, and is impossible if you can't tell a fault has
occurred.

It addresses a particular risk of circuits with high earth leakage -
it does not eliminate the risk completely - something that can never
be done. It does however reduce it for a marginal extra cost in
materials and effort. As with all engineering its a case of
compromise.

its marginal at best..

suppose its a simple circuit.. one socket two wires between the
socket and the consumer unit.

You really have no idea do you?

--
Adam

In article ,
John Rumm wrote:
On 23/08/2011 20:20, Dave Plowman (News) wrote:
In articleBemdnegRV7cjcc7TnZ2dnUVZ7sSdnZ2d@brightvie w.co.uk,
John wrote:
(As an aside, the wires should not be twisted).

Is the reason simply they may break - at some point in the future if
not at the time?

More a case of it making it harder to fault find later, plus a slight
increase in the chances that you will break a wire by work hardening it.

Ok, if that's the official view. Mine - having come across lots and lots
of poor connections on installations done by pros due to poor tightening
etc, is that I'll continue to twist conductors together here.

--
*I can see your point, but I still think you're full of ****.

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

On 23/08/2011 21:48, dennis@home wrote:


"John Rumm" wrote in message
o.uk...
On 23/08/2011 20:51, dennis@home wrote:


"John Rumm" wrote in message
o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a
radial circuit. Hence there are two paths to earth - and both
connections would have to fail to lose the earth at the socket. A
complete failure at one socket would not affect the earthing of the
others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a radial
without the ring at the first fault and the user will never know.

Which would be preferable to the alternate arrangement where it
degenerates into a section of a radial circuit being unearthed
altogether and the user not knowing.

In fact unless its tested you may never have the ring and the user
wouldn't be able to tell.

One would test just as one would for any other new circuit.

It really is a problem designing systems with redundancy that actually
work, and is impossible if you can't tell a fault has occurred.

It addresses a particular risk of circuits with high earth leakage -
it does not eliminate the risk completely - something that can never
be done. It does however reduce it for a marginal extra cost in
materials and effort. As with all engineering its a case of compromise.

its marginal at best..

No its not.

suppose its a simple circuit.. one socket two wires between the socket
and the consumer unit.

Not much point in doing it for a one socket circuit, you are not going
to amass enough leakage on a single socket to warrant high integrity
earthing anyway.

that is twice as many joints terminated as a single wire circuit.
so there is twice the rate of failure.

There are not "twice as many joints", there would be four - live,
neutral, earth, earth loop - so one extra. The one extra joint now means
you need two joint failures to leave the socket unearthed rather than one.

So that means the dual circuit is not twice as reliable as the single
circuit and the first fault will in the dual circuit will (on
average)occur in half the time the first fault will occur on the single
circuit. The second will occur somewhere near the time the first would
occur on the single circuit (being as it has half the failure rate due
to having half the components).
This is true for any replicated system where the faults are undetected
and not fixed.

And in English this time?

There are a load of equations that tell you how reliable a system is,
but they all assume you can detect the fault and hence repair it, which
you can't easily do in this case.

I think you are missing the point here. The object of the exercise is to
reduce the chances of leaving a section of circuit CPC floating with the
potential to source a significant current at mains voltage due to
leakage. Ensuring that each socket has two parallel earth connections in
no way hinders this. Using two terminals also halves the chance that a
single termination failure would result in this.

--
Cheers,

John.

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

"John Rumm" wrote in message
o.uk...
On 23/08/2011 21:48, dennis@home wrote:


"John Rumm" wrote in message
o.uk...
On 23/08/2011 20:51, dennis@home wrote:


"John Rumm" wrote in message
o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a
radial circuit. Hence there are two paths to earth - and both
connections would have to fail to lose the earth at the socket. A
complete failure at one socket would not affect the earthing of the
others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a radial
without the ring at the first fault and the user will never know.

Which would be preferable to the alternate arrangement where it
degenerates into a section of a radial circuit being unearthed
altogether and the user not knowing.

In fact unless its tested you may never have the ring and the user
wouldn't be able to tell.

One would test just as one would for any other new circuit.

It really is a problem designing systems with redundancy that actually
work, and is impossible if you can't tell a fault has occurred.

It addresses a particular risk of circuits with high earth leakage -
it does not eliminate the risk completely - something that can never
be done. It does however reduce it for a marginal extra cost in
materials and effort. As with all engineering its a case of compromise.

its marginal at best..

No its not.

suppose its a simple circuit.. one socket two wires between the socket
and the consumer unit.

Not much point in doing it for a one socket circuit, you are not going to
amass enough leakage on a single socket to warrant high integrity earthing
anyway.

that is twice as many joints terminated as a single wire circuit.
so there is twice the rate of failure.

There are not "twice as many joints", there would be four - live, neutral,
earth, earth loop - so one extra. The one extra joint now means you need
two joint failures to leave the socket unearthed rather than one.

But you have twice as many joints in the earth so twice the failure rate, no
way to know its failed and the second fault will leave it in exactly the
same state as the first failure in a normal circuit.

Where is the high integrity in a system where the faults occur at the same
rate and have the same effect?


So that means the dual circuit is not twice as reliable as the single
circuit and the first fault will in the dual circuit will (on
average)occur in half the time the first fault will occur on the single
circuit. The second will occur somewhere near the time the first would
occur on the single circuit (being as it has half the failure rate due
to having half the components).
This is true for any replicated system where the faults are undetected
and not fixed.

And in English this time?

There are a load of equations that tell you how reliable a system is,
but they all assume you can detect the fault and hence repair it, which
you can't easily do in this case.

I think you are missing the point here. The object of the exercise is to
reduce the chances of leaving a section of circuit CPC floating with the
potential to source a significant current at mains voltage due to leakage.
Ensuring that each socket has two parallel earth connections in no way
hinders this. Using two terminals also halves the chance that a single
termination failure would result in this.

You are missing the point.
read up about high reliability systems and failure rates versus time to
repair and it will all become clear.
I am not going to attempt to explain it any further than I already have as
its pointless trying.
You can either read about it or ignore me, take your pick.

On 25/08/2011 09:16, dennis@home wrote:


"John Rumm" wrote in message
o.uk...
On 23/08/2011 21:48, dennis@home wrote:


"John Rumm" wrote in message
o.uk...
On 23/08/2011 20:51, dennis@home wrote:


"John Rumm" wrote in message
o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a
radial circuit. Hence there are two paths to earth - and both
connections would have to fail to lose the earth at the socket. A
complete failure at one socket would not affect the earthing of the
others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a radial
without the ring at the first fault and the user will never know.

Which would be preferable to the alternate arrangement where it
degenerates into a section of a radial circuit being unearthed
altogether and the user not knowing.

In fact unless its tested you may never have the ring and the user
wouldn't be able to tell.

One would test just as one would for any other new circuit.

It really is a problem designing systems with redundancy that actually
work, and is impossible if you can't tell a fault has occurred.

It addresses a particular risk of circuits with high earth leakage -
it does not eliminate the risk completely - something that can never
be done. It does however reduce it for a marginal extra cost in
materials and effort. As with all engineering its a case of compromise.

its marginal at best..

No its not.

suppose its a simple circuit.. one socket two wires between the socket
and the consumer unit.

Not much point in doing it for a one socket circuit, you are not going
to amass enough leakage on a single socket to warrant high integrity
earthing anyway.

that is twice as many joints terminated as a single wire circuit.
so there is twice the rate of failure.

There are not "twice as many joints", there would be four - live,
neutral, earth, earth loop - so one extra. The one extra joint now
means you need two joint failures to leave the socket unearthed rather
than one.

But you have twice as many joints in the earth so twice the failure
rate, no way to know its failed and the second fault will leave it in
exactly the same state as the first failure in a normal circuit.

I think here is one of the false assumptions upon which your argument
flounders...

Firstly you are assuming that a "normal" circuit would be wired with a
single earth connection at each socket. Whereas, most electricians I
have observed, will use both terminals (myself included) when two
terminals are provided. The reason knocks on to the second part of your
assumption; that two connections are of the same inherent reliability as
one, and hence the benefit is doubled along with the probability of
failure and hence you have a zero sum game. This is not the case IME.
When dealing with loose sleeved wires such as the earth, it is
inherently easier to make high quality terminations of one wire per
terminal than two. There is also less possibility of a shift in the wire
dressing will alter the clamping pressure in the terminal.

You are also ignoring the benefit provided by better earth level
clamping provided by having at least twice (and possibly) more CSA of
copper clamping the leakage potential on the CPC.

Where is the high integrity in a system where the faults occur at the
same rate and have the same effect?

None, however that is not what we are dealing with here.

Also note that in a commercial environment where use of this circuit
topology is more likely, the fact that you have even identified the
circuit as a high risk one, suggests a more rigorous routine testing
would be appropriate than for a general purpose circuit. This would
reduce the likelihood of a fault remaining undetected.

So that means the dual circuit is not twice as reliable as the single
circuit and the first fault will in the dual circuit will (on
average)occur in half the time the first fault will occur on the single
circuit. The second will occur somewhere near the time the first would
occur on the single circuit (being as it has half the failure rate due
to having half the components).
This is true for any replicated system where the faults are undetected
and not fixed.

And in English this time?

There are a load of equations that tell you how reliable a system is,
but they all assume you can detect the fault and hence repair it, which
you can't easily do in this case.

I think you are missing the point here. The object of the exercise is
to reduce the chances of leaving a section of circuit CPC floating
with the potential to source a significant current at mains voltage
due to leakage. Ensuring that each socket has two parallel earth
connections in no way hinders this. Using two terminals also halves
the chance that a single termination failure would result in this.

You are missing the point.
read up about high reliability systems and failure rates versus time to
repair and it will all become clear.

No need to "read up" on it Dennis - I seem to recall "testing and
maintenance" and "reliability engineering" where not particularly
difficult courses when I studied them.

I am not going to attempt to explain it any further than I already have
as its pointless trying.

I don't believe a word of it Dennis - you like nothing better than an
argument descending into ever decreasing circles.

You can either read about it or ignore me, take your pick.

Oh tempting.... could I use a grubbing mattock rather than a pick?

--
Cheers,

John.

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

"John Rumm" wrote in message
...
On 25/08/2011 09:16, dennis@home wrote:


"John Rumm" wrote in message
o.uk...
On 23/08/2011 21:48, dennis@home wrote:


"John Rumm" wrote in message
o.uk...
On 23/08/2011 20:51, dennis@home wrote:


"John Rumm" wrote in message
o.uk...

Remember with high integrity earthing, the CPC is a ring, even on a
radial circuit. Hence there are two paths to earth - and both
connections would have to fail to lose the earth at the socket. A
complete failure at one socket would not affect the earthing of the
others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a
radial
without the ring at the first fault and the user will never know.

Which would be preferable to the alternate arrangement where it
degenerates into a section of a radial circuit being unearthed
altogether and the user not knowing.

In fact unless its tested you may never have the ring and the user
wouldn't be able to tell.

One would test just as one would for any other new circuit.

It really is a problem designing systems with redundancy that
actually
work, and is impossible if you can't tell a fault has occurred.

It addresses a particular risk of circuits with high earth leakage -
it does not eliminate the risk completely - something that can never
be done. It does however reduce it for a marginal extra cost in
materials and effort. As with all engineering its a case of
compromise.

its marginal at best..

No its not.

suppose its a simple circuit.. one socket two wires between the socket
and the consumer unit.

Not much point in doing it for a one socket circuit, you are not going
to amass enough leakage on a single socket to warrant high integrity
earthing anyway.

that is twice as many joints terminated as a single wire circuit.
so there is twice the rate of failure.

There are not "twice as many joints", there would be four - live,
neutral, earth, earth loop - so one extra. The one extra joint now
means you need two joint failures to leave the socket unearthed rather
than one.

But you have twice as many joints in the earth so twice the failure
rate, no way to know its failed and the second fault will leave it in
exactly the same state as the first failure in a normal circuit.

I think here is one of the false assumptions upon which your argument
flounders...

Firstly you are assuming that a "normal" circuit would be wired with a
single earth connection at each socket. Whereas, most electricians I have
observed, will use both terminals (myself included) when two terminals are
provided. The reason knocks on to the second part of your assumption; that
two connections are of the same inherent reliability as one, and hence the
benefit is doubled along with the probability of failure and hence you
have a zero sum game. This is not the case IME.

Your experience is irrelevant.
Try proving that two connections are as reliable as one.
You can't as it just isn't true.

When dealing with loose sleeved wires such as the earth, it is inherently
easier to make high quality terminations of one wire per terminal than
two. There is also less possibility of a shift in the wire dressing will
alter the clamping pressure in the terminal.

You are also ignoring the benefit provided by better earth level clamping
provided by having at least twice (and possibly) more CSA of copper
clamping the leakage potential on the CPC.

Where is the high integrity in a system where the faults occur at the
same rate and have the same effect?

None, however that is not what we are dealing with here.

Also note that in a commercial environment where use of this circuit
topology is more likely, the fact that you have even identified the
circuit as a high risk one, suggests a more rigorous routine testing would
be appropriate than for a general purpose circuit. This would reduce the
likelihood of a fault remaining undetected.

So you are now saying they are going to disassemble the circuit and test it
and then reassemble it frequently so that dormant faults are found, without
actually making it less reliable by all the messing about?
You appear to gloss over the fact that its difficult to test the circuit
once its complete in the first place. just buzzing a few wires isn't going
to detect all possible faults and taking it apart and reassembling it may
well induce the same faults when you do it.


So that means the dual circuit is not twice as reliable as the single
circuit and the first fault will in the dual circuit will (on
average)occur in half the time the first fault will occur on the single
circuit. The second will occur somewhere near the time the first would
occur on the single circuit (being as it has half the failure rate due
to having half the components).
This is true for any replicated system where the faults are undetected
and not fixed.

And in English this time?

There are a load of equations that tell you how reliable a system is,
but they all assume you can detect the fault and hence repair it, which
you can't easily do in this case.

I think you are missing the point here. The object of the exercise is
to reduce the chances of leaving a section of circuit CPC floating
with the potential to source a significant current at mains voltage
due to leakage. Ensuring that each socket has two parallel earth
connections in no way hinders this. Using two terminals also halves
the chance that a single termination failure would result in this.

You are missing the point.
read up about high reliability systems and failure rates versus time to
repair and it will all become clear.

No need to "read up" on it Dennis - I seem to recall "testing and
maintenance" and "reliability engineering" where not particularly
difficult courses when I studied them.

However you didn't understand them it appears, assuming you did such a
course.

dennis@home wrote:
"John Rumm" wrote in message
...
On 25/08/2011 09:16, dennis@home wrote:


"John Rumm" wrote in message
o.uk...
On 23/08/2011 21:48, dennis@home wrote:


"John Rumm" wrote in message
o.uk...
On 23/08/2011 20:51, dennis@home wrote:


"John Rumm" wrote in message
o.uk...

Remember with high integrity earthing, the CPC is a ring, even
on a radial circuit. Hence there are two paths to earth - and
both connections would have to fail to lose the earth at the
socket. A complete failure at one socket would not affect the
earthing of the others.

An interesting idea.. but flawed.
Unless you test the ring periodically it will degenerate into a
radial
without the ring at the first fault and the user will never
know.

Which would be preferable to the alternate arrangement where it
degenerates into a section of a radial circuit being unearthed
altogether and the user not knowing.

In fact unless its tested you may never have the ring and the
user wouldn't be able to tell.

One would test just as one would for any other new circuit.

It really is a problem designing systems with redundancy that
actually
work, and is impossible if you can't tell a fault has occurred.

It addresses a particular risk of circuits with high earth
leakage - it does not eliminate the risk completely - something
that can never be done. It does however reduce it for a marginal
extra cost in materials and effort. As with all engineering its
a case of compromise.

its marginal at best..

No its not.

suppose its a simple circuit.. one socket two wires between the
socket and the consumer unit.

Not much point in doing it for a one socket circuit, you are not
going to amass enough leakage on a single socket to warrant high
integrity earthing anyway.

that is twice as many joints terminated as a single wire circuit.
so there is twice the rate of failure.

There are not "twice as many joints", there would be four - live,
neutral, earth, earth loop - so one extra. The one extra joint now
means you need two joint failures to leave the socket unearthed
rather than one.

But you have twice as many joints in the earth so twice the failure
rate, no way to know its failed and the second fault will leave it
in exactly the same state as the first failure in a normal circuit.

I think here is one of the false assumptions upon which your argument
flounders...

Firstly you are assuming that a "normal" circuit would be wired with
a single earth connection at each socket. Whereas, most electricians
I have observed, will use both terminals (myself included) when two
terminals are provided. The reason knocks on to the second part of
your assumption; that two connections are of the same inherent
reliability as one, and hence the benefit is doubled along with the
probability of failure and hence you have a zero sum game. This is
not the case IME.

Your experience is irrelevant.
Try proving that two connections are as reliable as one.
You can't as it just isn't true.

When dealing with loose sleeved wires such as the earth, it is
inherently easier to make high quality terminations of one wire per
terminal than two. There is also less possibility of a shift in the
wire dressing will alter the clamping pressure in the terminal.

You are also ignoring the benefit provided by better earth level
clamping provided by having at least twice (and possibly) more CSA
of copper clamping the leakage potential on the CPC.

Where is the high integrity in a system where the faults occur at
the same rate and have the same effect?

None, however that is not what we are dealing with here.

Also note that in a commercial environment where use of this circuit
topology is more likely, the fact that you have even identified the
circuit as a high risk one, suggests a more rigorous routine testing
would be appropriate than for a general purpose circuit. This would
reduce the likelihood of a fault remaining undetected.

So you are now saying they are going to disassemble the circuit and
test it and then reassemble it frequently so that dormant faults are
found, without actually making it less reliable by all the messing
about? You appear to gloss over the fact that its difficult to test the
circuit once its complete in the first place. just buzzing a few
wires isn't going to detect all possible faults and taking it apart
and reassembling it may well induce the same faults when you do it.

After the intitial inspection the circuit can easily be tested at any time
without any disassembly in a matter of minutes.

--
Adam

On 25/08/2011 20:34, dennis@home wrote:

There are not "twice as many joints", there would be four - live,
neutral, earth, earth loop - so one extra. The one extra joint now
means you need two joint failures to leave the socket unearthed rather
than one.

But you have twice as many joints in the earth so twice the failure
rate, no way to know its failed and the second fault will leave it in
exactly the same state as the first failure in a normal circuit.

I think here is one of the false assumptions upon which your argument
flounders...

Firstly you are assuming that a "normal" circuit would be wired with a
single earth connection at each socket. Whereas, most electricians I
have observed, will use both terminals (myself included) when two
terminals are provided. The reason knocks on to the second part of
your assumption; that two connections are of the same inherent
reliability as one, and hence the benefit is doubled along with the
probability of failure and hence you have a zero sum game. This is not
the case IME.

Your experience is irrelevant.
Try proving that two connections are as reliable as one.

I can satisfy myself that after many hundreds of inspected joints that
this is the case. You can of course suit yourself.

With wiring in general, some failure modes are more common than others.
Loose sleeved CPCs tend to be more problematical when there are several
in a screw terminal.

Remember also that the IET armed with the expertise of many competent
engineers, and access to far more empirical and experimental data that
either of us, also promote this system. It is not something I invented
just to wind you up.

You can't as it just isn't true.

In your opinion, which you are most welcome to.

When dealing with loose sleeved wires such as the earth, it is
inherently easier to make high quality terminations of one wire per
terminal than two. There is also less possibility of a shift in the
wire dressing will alter the clamping pressure in the terminal.

You are also ignoring the benefit provided by better earth level
clamping provided by having at least twice (and possibly) more CSA of
copper clamping the leakage potential on the CPC.

Where is the high integrity in a system where the faults occur at the
same rate and have the same effect?

None, however that is not what we are dealing with here.

Also note that in a commercial environment where use of this circuit
topology is more likely, the fact that you have even identified the
circuit as a high risk one, suggests a more rigorous routine testing
would be appropriate than for a general purpose circuit. This would
reduce the likelihood of a fault remaining undetected.

So you are now saying they are going to disassemble the circuit and test
it and then reassemble it frequently so that dormant faults are found,
without actually making it less reliable by all the messing about?

No. I am saying in a commercial environment it is appropriate to carry
out periodic testing. This does not necessarily need to be invasive, but
can be conducted with an earth loop tester and some inspection.

You appear to gloss over the fact that its difficult to test the circuit
once its complete in the first place.

You do write some crap... Its hardly any harder to test than a bog
standard radial, and certainly no harder than a ring circuit - and
testing that is routine.

just buzzing a few wires isn't
going to detect all possible faults and taking it apart and reassembling
it may well induce the same faults when you do it.

Have a read of the on site guide - it explains in detail how to test
basic circuits. It really is not rocket science.

You are missing the point.
read up about high reliability systems and failure rates versus time to
repair and it will all become clear.

No need to "read up" on it Dennis - I seem to recall "testing and
maintenance" and "reliability engineering" where not particularly
difficult courses when I studied them.

However you didn't understand them it appears, assuming you did such a
course.

Got a pass with distinction in both old bean...


--
Cheers,

John.

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

"John Rumm" wrote in message
...
On 25/08/2011 20:34, dennis@home wrote:

There are not "twice as many joints", there would be four - live,
neutral, earth, earth loop - so one extra. The one extra joint now
means you need two joint failures to leave the socket unearthed rather
than one.

But you have twice as many joints in the earth so twice the failure
rate, no way to know its failed and the second fault will leave it in
exactly the same state as the first failure in a normal circuit.

I think here is one of the false assumptions upon which your argument
flounders...

Firstly you are assuming that a "normal" circuit would be wired with a
single earth connection at each socket. Whereas, most electricians I
have observed, will use both terminals (myself included) when two
terminals are provided. The reason knocks on to the second part of
your assumption; that two connections are of the same inherent
reliability as one, and hence the benefit is doubled along with the
probability of failure and hence you have a zero sum game. This is not
the case IME.

Your experience is irrelevant.
Try proving that two connections are as reliable as one.

I can satisfy myself that after many hundreds of inspected joints that
this is the case. You can of course suit yourself.

You can if you want but i work with real numbers not a few hundred.
If you really think you can find the failure rate of such simple circuits
from inspecting such low numbers then you really don't have a clue.


With wiring in general, some failure modes are more common than others.
Loose sleeved CPCs tend to be more problematical when there are several in
a screw terminal.

Remember also that the IET armed with the expertise of many competent
engineers, and access to far more empirical and experimental data that
either of us, also promote this system. It is not something I invented
just to wind you up.

The IET have strange views as many of their members will tell you.


You can't as it just isn't true.

In your opinion, which you are most welcome to.

When dealing with loose sleeved wires such as the earth, it is
inherently easier to make high quality terminations of one wire per
terminal than two. There is also less possibility of a shift in the
wire dressing will alter the clamping pressure in the terminal.

You are also ignoring the benefit provided by better earth level
clamping provided by having at least twice (and possibly) more CSA of
copper clamping the leakage potential on the CPC.

Where is the high integrity in a system where the faults occur at the
same rate and have the same effect?

None, however that is not what we are dealing with here.

Also note that in a commercial environment where use of this circuit
topology is more likely, the fact that you have even identified the
circuit as a high risk one, suggests a more rigorous routine testing
would be appropriate than for a general purpose circuit. This would
reduce the likelihood of a fault remaining undetected.

So you are now saying they are going to disassemble the circuit and test
it and then reassemble it frequently so that dormant faults are found,
without actually making it less reliable by all the messing about?

No. I am saying in a commercial environment it is appropriate to carry out
periodic testing. This does not necessarily need to be invasive, but can
be conducted with an earth loop tester and some inspection.

You appear to gloss over the fact that its difficult to test the circuit
once its complete in the first place.

You do write some crap... Its hardly any harder to test than a bog
standard radial, and certainly no harder than a ring circuit - and testing
that is routine.

just buzzing a few wires isn't
going to detect all possible faults and taking it apart and reassembling
it may well induce the same faults when you do it.

Have a read of the on site guide - it explains in detail how to test basic
circuits. It really is not rocket science.

I would like to see you test for the faults without taking stuff apart with
the kit electricians use.
that is the average electrician wouldn't have a clue or the equipment needed
to test the circuit with dismantling it and prove it was actually working as
intended after assembly. That would mean as the user sees the equipment BTW.

You are missing the point.
read up about high reliability systems and failure rates versus time to
repair and it will all become clear.

No need to "read up" on it Dennis - I seem to recall "testing and
maintenance" and "reliability engineering" where not particularly
difficult courses when I studied them.

However you didn't understand them it appears, assuming you did such a
course.

Got a pass with distinction in both old bean...

Really? That means they aren't worth the paper they are written on.

dennis@home wrote:

You can if you want but i work with real numbers not a few hundred.
If you really think you can find the failure rate of such simple
circuits from inspecting such low numbers then you really don't have
a clue.

Says the man who can count up to twelve using his fingers.


With wiring in general, some failure modes are more common than
others. Loose sleeved CPCs tend to be more problematical when there
are several in a screw terminal.

Remember also that the IET armed with the expertise of many competent
engineers, and access to far more empirical and experimental data
that either of us, also promote this system. It is not something I
invented just to wind you up.

The IET have strange views as many of their members will tell you.

So says the bloke who is unable to use an induction hob without causing a
fire.

You do write some crap... Its hardly any harder to test than a bog
standard radial, and certainly no harder than a ring circuit - and
testing that is routine.

just buzzing a few wires isn't
going to detect all possible faults and taking it apart and
reassembling it may well induce the same faults when you do it.

Have a read of the on site guide - it explains in detail how to test
basic circuits. It really is not rocket science.

I would like to see you test for the faults without taking stuff
apart with the kit electricians use.

It would take 5 seconds to prove that both earth circiuts are intact.,

that is the average electrician wouldn't have a clue or the equipment
needed to test the circuit with dismantling it and prove it was
actually working as intended after assembly. That would mean as the
user sees the equipment BTW.
You are missing the point.
read up about high reliability systems and failure rates versus
time to repair and it will all become clear.

No need to "read up" on it Dennis - I seem to recall "testing and
maintenance" and "reliability engineering" where not particularly
difficult courses when I studied them.

However you didn't understand them it appears, assuming you did
such a course.

Got a pass with distinction in both old bean...

Really? That means they aren't worth the paper they are written on.

So says the bloke that can't pass water without needing a change of
underwear.

--
Adam

ARWadsworth wrote:
dennis@home wrote:

I would like to see you test for the faults without taking stuff
apart with the kit electricians use.

It would take 5 seconds to prove that both earth circiuts are intact.,

I'd like to know how you do that without disconnecting anything, or
using test gear I'd only expect to find in a lab.

We live and learn.

--
Tciao for Now!

John.

John Williamson wrote:
ARWadsworth wrote:
dennis@home wrote:

I would like to see you test for the faults without taking stuff
apart with the kit electricians use.

It would take 5 seconds to prove that both earth circiuts are
intact.,
I'd like to know how you do that without disconnecting anything, or
using test gear I'd only expect to find in a lab.

We live and learn.

A simple earth loop reading will do the trick.

--
Adam

ARWadsworth wrote:
John Williamson wrote:
ARWadsworth wrote:
dennis@home wrote:

I would like to see you test for the faults without taking stuff
apart with the kit electricians use.
It would take 5 seconds to prove that both earth circiuts are
intact.,
I'd like to know how you do that without disconnecting anything, or
using test gear I'd only expect to find in a lab.

We live and learn.

A simple earth loop reading will do the trick.

Which, according to one set of testing instructions I've seen involves
making and breaking a number of connections.

--
Tciao for Now!

John.

John Williamson wrote:
ARWadsworth wrote:
John Williamson wrote:
ARWadsworth wrote:
dennis@home wrote:

I would like to see you test for the faults without taking stuff
apart with the kit electricians use.
It would take 5 seconds to prove that both earth circiuts are
intact.,
I'd like to know how you do that without disconnecting anything, or
using test gear I'd only expect to find in a lab.

We live and learn.

A simple earth loop reading will do the trick.

Which, according to one set of testing instructions I've seen involves
making and breaking a number of connections.

Are you are thinking about an earth loop reading for the origin of the
supply where you would need to disconnect main equipotential cables?
--
Adam

On Aug 26, 5:30*pm, John Williamson
wrote:
Which, according to one set of testing instructions I've seen involves
making and breaking a number of connections.

But what's that number, and where are they?

You can manage to do an awful lot of disconnections for testing if
they're all accessible and all done at one location, such as the CU.
The killer for time spent is when you have to walk the length of a
circuit, doing things at intervals around it.

Andy Dingley wrote:
On Aug 26, 5:30 pm, John Williamson
wrote:
Which, according to one set of testing instructions I've seen involves
making and breaking a number of connections.

But what's that number, and where are they?

You can manage to do an awful lot of disconnections for testing if
they're all accessible and all done at one location, such as the CU.
The killer for time spent is when you have to walk the length of a
circuit, doing things at intervals around it.

In the distribution box, one per ring.

Then you walk round with the meter testing sockets, or use a *long* lead
on the test meter.

However, the claim that prompted my question was that it could be done
without breaking *any* connections, using standard test gear, on a
circuit with dual earth connections.

--
Tciao for Now!

John.

ARWadsworth wrote:
John Williamson wrote:
ARWadsworth wrote:
John Williamson wrote:
ARWadsworth wrote:
dennis@home wrote:

I would like to see you test for the faults without taking stuff
apart with the kit electricians use.
It would take 5 seconds to prove that both earth circiuts are
intact.,
I'd like to know how you do that without disconnecting anything, or
using test gear I'd only expect to find in a lab.

We live and learn.
A simple earth loop reading will do the trick.

Which, according to one set of testing instructions I've seen involves
making and breaking a number of connections.

Are you are thinking about an earth loop reading for the origin of the
supply where you would need to disconnect main equipotential cables?

No, an earth loop test for each socket, which involves disturbing
connections in the consumer unit.

It was claimed that this test could be done on a system with two earths
using standard test gear without disturbing the installation.

--
Tciao for Now!

John.

"Andy Dingley" wrote in message
...
On Aug 26, 5:30 pm, John Williamson
wrote:
Which, according to one set of testing instructions I've seen involves
making and breaking a number of connections.

But what's that number, and where are they?

You can manage to do an awful lot of disconnections for testing if
they're all accessible and all done at one location, such as the CU.
The killer for time spent is when you have to walk the length of a
circuit, doing things at intervals around it.

The real killer is that after you reconnect it you can't then test it and it
may well have developed a fault due to the act of reconnecting it.
You can't claim its has a high integrity when the mere act of testing it may
cause an undetectable fault.
Not unless you redefine what high integrity means.

On 26/08/2011 16:48, ARWadsworth wrote:

So says the bloke that can't pass water without needing a change of
underwear.

I think dennis has just turned into dribble - he seems to be looping.

Someone reset him...


--
Cheers,

John.

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

On 26/08/2011 16:57, John Williamson wrote:
ARWadsworth wrote:
dennis@home wrote:

I would like to see you test for the faults without taking stuff
apart with the kit electricians use.

It would take 5 seconds to prove that both earth circiuts are intact.,

I'd like to know how you do that without disconnecting anything, or
using test gear I'd only expect to find in a lab.

We live and learn.

One would typically test a circuit at the CU when installing it (i.e.
before assembling!), when you have access to the origin of the cabling.
A round trip resistance check on the earth will tell you most of what
you need to know alongside the usual tests for a radial power circuit. A
16th edition style high current loop test (with RCD wired out) would be
worth doing on the complete circuit.

For periodic testing. a non tripping earth loop test, repeated at a few
sockets along the circuit will let you verify that both earth paths are
still in place.


--
Cheers,

John.

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

John Williamson wrote:
It would take 5 seconds to prove that both earth circiuts are
intact.,
I'd like to know how you do that without disconnecting anything,
or using test gear I'd only expect to find in a lab.

We live and learn.
A simple earth loop reading will do the trick.

Which, according to one set of testing instructions I've seen
involves making and breaking a number of connections.

Are you are thinking about an earth loop reading for the origin of
the supply where you would need to disconnect main equipotential
cables?

No, an earth loop test for each socket, which involves disturbing
connections in the consumer unit.

Then you are thinking of the resistance readings for the ring. That is not
needed to prove continuity after the initial testing and commissioning.

It was claimed that this test could be done on a system with two
earths using standard test gear without disturbing the installation.

When the system is installed then you would test the continuity of the ring.
This will need the ring to be disconnected from the bus bar or be tested
before connection. But you also take an earth loop reading at the final
socket on the circuit (a simple plug in test).
That value will not alter if the ring remains in place[1] and you can check
the circuit at any time by plugging the earth loop tester into the final
socket at any time.


[1] If the supply characteristics alter then they would alter the reading
however you would still only need to test the incoming supply to correct the
reading (or use a test socket), and there would still be no need to
disconnect anything.

--
Adam

On 26/08/2011 16:48, ARWadsworth wrote:
wrote:

You can if you want but i work with real numbers not a few hundred.
If you really think you can find the failure rate of such simple
circuits from inspecting such low numbers then you really don't have
a clue.

Says the man who can count up to twelve using his fingers.


With wiring in general, some failure modes are more common than
others. Loose sleeved CPCs tend to be more problematical when there
are several in a screw terminal.

Remember also that the IET armed with the expertise of many competent
engineers, and access to far more empirical and experimental data
that either of us, also promote this system. It is not something I
invented just to wind you up.

The IET have strange views as many of their members will tell you.

So says the bloke who is unable to use an induction hob without causing a
fire.

You do write some crap... Its hardly any harder to test than a bog
standard radial, and certainly no harder than a ring circuit - and
testing that is routine.

just buzzing a few wires isn't
going to detect all possible faults and taking it apart and
reassembling it may well induce the same faults when you do it.

Have a read of the on site guide - it explains in detail how to test
basic circuits. It really is not rocket science.

I would like to see you test for the faults without taking stuff
apart with the kit electricians use.

It would take 5 seconds to prove that both earth circiuts are intact.,

that is the average electrician wouldn't have a clue or the equipment
needed to test the circuit with dismantling it and prove it was
actually working as intended after assembly. That would mean as the
user sees the equipment BTW.
You are missing the point.
read up about high reliability systems and failure rates versus
time to repair and it will all become clear.

No need to "read up" on it Dennis - I seem to recall "testing and
maintenance" and "reliability engineering" where not particularly
difficult courses when I studied them.

However you didn't understand them it appears, assuming you did
such a course.

Got a pass with distinction in both old bean...

Really? That means they aren't worth the paper they are written on.

So says the bloke that can't pass water without needing a change of
underwear.

Can he claim back the VAT on that underwear?

--
Dave - The Medway Handyman www.medwayhandyman.co.uk

On 26/08/2011 21:03, John Rumm wrote:
On 26/08/2011 16:48, ARWadsworth wrote:

So says the bloke that can't pass water without needing a change of
underwear.

I think dennis has just turned into dribble - he seems to be looping.

Someone reset him...


I think he is secretly Count Arthur Strong;

Count Arthur Strong is a former variety star living in the North of
England. The Count, now in his old age, has delusions of grandeur. He
has selective memory loss, never hearing what he doesn't want to and
malapropism-itis, which result in his confusing anyone he happens to be
talking to and even confusing himself. However, he more often than not
blames the people he is talking to for causing the confusion in the
first place. On the few occasions Count Arthur does realise that it he
who is in the wrong, he tries to lie out of his predicament, often
unsuccessfully.

A typical conversation for the Count will involve his confusing both
himself and others, while becoming drastically sidetracked from the
matter in hand. He is usually oblivious to the chaos he causes, often
blaming his interlocutors for any confusion. On the rare occasions he
realises he is at fault, he often attempts to divert the blame by lying.
Inevitably becoming confused by his own lies, his last resort is usually
to claim he was recording a stunt for a hidden camera show.


Fits like a glove......
--
Dave - The Medway Handyman www.medwayhandyman.co.uk