I was asked by a friend to investigate a seemingly faulty 20A DP
switch for a washing machine today.

In hindsight slightly unwisely, I unscrewed the switch and pulled it
forward to be rewarded with a flash, bang and the appropriate cloud of
noxious smoke ! Hey isn't it great when you get the pyrotecniks
rather than just something going dead.

Anyway my guess is that the line terminal had not been tightened
properly originally, had over heated, the plastic broken down and my
approach had resulted in the line terminal breaking free and coming in
contact with the earth lead.

The fuse in the CU did not rupture !!

The switch was replaced.

The question arises now is should I strongly advise my friend to have
his fuses CU replaced with a modern one; the emphasis is on the
'strongly' as my feeling is that despite a large flash/short as this
was, the fuse did not protect the system as an RCD or MCB would have
done. In fact an RCD would probably have tripped out long before I
was asked to look and would have given the protection that the house
should have (said having just has my own RCD trip and finding that it
was due to the oven fan becoming leaky).

Rob

robgraham wrote:

In hindsight slightly unwisely, I unscrewed the switch and pulled it
forward to be rewarded with a flash, bang and the appropriate cloud of
noxious smoke ! Hey isn't it great when you get the pyrotecniks
rather than just something going dead.

Helps liven things up! ;-)

Anyway my guess is that the line terminal had not been tightened
properly originally, had over heated, the plastic broken down and my
approach had resulted in the line terminal breaking free and coming in
contact with the earth lead.

The fuse in the CU did not rupture !!

It might not on a very brief arc over. Much the same happens when a
filament lamp blows in some cases.

The question arises now is should I strongly advise my friend to have
his fuses CU replaced with a modern one; the emphasis is on the
'strongly' as my feeling is that despite a large flash/short as this
was, the fuse did not protect the system as an RCD or MCB would have
done. In fact an RCD would probably have tripped out long before I
was asked to look and would have given the protection that the house

Well there are pros and cons. Have a look at the lists and see which
apply most in this case:

http://wiki.diyfaq.org.uk/index.php?...f or_a_change


--
Cheers,

John.

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

On Aug 1, 12:44*am, robgraham wrote:
I was asked by a friend to investigate a seemingly faulty 20A DP
switch for a washing machine today.

In hindsight slightly unwisely, I unscrewed the switch and pulled it
forward to be rewarded with a flash, bang and the appropriate cloud of
noxious smoke ! *Hey isn't it great when you get the pyrotecniks
rather than just something going dead.

Anyway my guess is that the line terminal had not been tightened
properly originally, had over heated, the plastic broken down and my
approach had resulted in the line terminal breaking free and coming in
contact with the earth lead.

The fuse in the CU did not rupture !!

not unusual.

The switch was replaced.

The question arises now is should I strongly advise my friend to have
his fuses CU replaced with a modern one; the emphasis is on the
'strongly' as my feeling is that despite a large flash/short as this
was, the fuse did not protect the system as an RCD or MCB would have
done. *In fact an RCD would probably have tripped out long before I
was asked to look and would have given the protection that the house
should have (said having just has my own RCD trip and finding that it
was due to the oven fan becoming leaky).

Rob

Rewirable fuses are still fully compliant for new installation. You'd
derive very little safety benefit from adding MCBs. The reason the
fuses didnt pop is that any trip device takes a cvertain amount of i
times t to blow, and the fault, while it may have looked impressive,
didnt draw enough i x t, and the fault blew itself open circuit first.
You may have been scared by this, but safetywise its pretty much a non-
issue.

http://www.wiki.diyfaq.org.uk/index.php?title=Fuse
http://www.wiki.diyfaq.org.uk/index.php?title=MCB
http://www.wiki.diyfaq.org.uk/index.php?title=RCD


NT

wrote:

Rewirable fuses are still fully compliant for new installation. You'd
derive very little safety benefit from adding MCBs. The reason the
fuses didnt pop is that any trip device takes a cvertain amount of i
times t to blow, and the fault, while it may have looked impressive,
didnt draw enough i x t, and the fault blew itself open circuit first.
You may have been scared by this, but safetywise its pretty much a non-
issue.

While this is true, there are two caveats worth mentioning: If the
cables are the older style PVC with only a 1mm^2 CPC (modern cable has
1.5mm^2) then it is worth moving away from rewireable fuses since the
protection will be marginal or insufficient in many cases. If the power
(i.e. socket) circuits currently have no RCD protection then again it is
worth introducing this, which realistically will also mean a CU swap.

--
Cheers,

John.

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

In article
,
robgraham wrote:
I was asked by a friend to investigate a seemingly faulty 20A DP
switch for a washing machine today.

In hindsight slightly unwisely, I unscrewed the switch and pulled it
forward to be rewarded with a flash, bang and the appropriate cloud of
noxious smoke ! Hey isn't it great when you get the pyrotecniks
rather than just something going dead.

It's total madness starting to investigate a fault with the power switched
on - especially on a strange installation where you've no idea if even the
earthing is correctly done.

Most of these sort of faults can be sorted with a simple inspection -
loose wires etc - and you don't need the power on for that.

--
*Real women don't have hot flashes, they have power surges.

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

"John Rumm" wrote

While this is true, there are two caveats worth mentioning: If the cables
are the older style PVC with only a 1mm^2 CPC (modern cable has 1.5mm^2)
then it is worth moving away from rewireable fuses since the protection
will be marginal or insufficient in many cases. If the power (i.e. socket)
circuits currently have no RCD protection then again it is worth
introducing this, which realistically will also mean a CU swap.

--
Cheers,

John.

AIUI, the 17th Edition is now requiring RCD protection for any buried cables
that are not either in earthed conduit or 50mm from the wall surface.
This applies to new installs/modifications only though.

Phil

robgraham wrote:

The question arises now is should I strongly advise my friend to have
his fuses CU replaced with a modern one; the emphasis is on the
'strongly'

To endorse what others have said, I don't think you should look at the
consumer unit in isolation. If danger lurks it's likely to be out in
the installation - as you discovered - and just modernising the
overcurrent protection is a bit like adding airbags to a car with no brakes.

I suggest doing, or paying for someone to do, a full PIR first. Then
assess what is found and effect appropriate improvements, prioritising
according to budget, if that's a constraint.

the fuse did not protect the system as an RCD or MCB would have
done.

You did check that the fuse hadn't been replaced by the proverbial 6
inch nail?

If the CU in question is the Wylex standard type, or one of its clones,
a worthwhile low-cost upgrade is to replace the rewireable fuses and
fuse carriers with HRC cartridge fuses:
http://www.tlc-direct.co.uk/Main_Ind...ers/index.html

In fact an RCD would probably have tripped out long before I
was asked to look and would have given the protection that the house
should have (said having just has my own RCD trip and finding that it
was due to the oven fan becoming leaky).

I guess that if you do replace the whole consumer unit now you'd have to
follow the 17th edition and provide suitably divided RCD protection
for everything. A sensible minimum though might be to just add a single
30 mA RCD (in separate enclosure, after the fuse) for the downstairs
ring circuit, thus covering the sockets likely to be used to feed
portable equipment outdoors.

--
Andy

On 1 Aug, 08:17, "Dave Plowman (News)" wrote:
In article
,
* *robgraham wrote:

I was asked by a friend to investigate a seemingly faulty 20A DP
switch for a washing machine today.
In hindsight slightly unwisely, I unscrewed the switch and pulled it
forward to be rewarded with a flash, bang and the appropriate cloud of
noxious smoke ! *Hey isn't it great when you get the pyrotecniks
rather than just something going dead.

It's total madness starting to investigate a fault with the power switched
on - especially on a strange installation where you've no idea if even the
earthing is correctly done.

Most of these sort of faults can be sorted with a simple inspection -
loose wires etc - and you don't need the power on for that.

--
*Real women don't have hot flashes, they have power surges.

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

Yes Dave, and hindsight is a great instructor. At 66 and a lifetime's
messing about with electrical installations, this is the first time
that's happened to me and although your advice is absolutely correct,
worth giving and will I assure you be followed in future, I note with
interest that none of those whom I hoped would answer my original post
felt it necessary to comment on my possible rashness - one could read
in that, that they would have done the same.

Otherwise, thanks guys - the topic will be 'discussed' therefore,
rather than 'strongly advised'

Rob

In article
,
robgraham wrote:
It's total madness starting to investigate a fault with the power
switched on - especially on a strange installation where you've no
idea if even the earthing is correctly done.

Most of these sort of faults can be sorted with a simple inspection -
loose wires etc - and you don't need the power on for that.

Yes Dave, and hindsight is a great instructor. At 66 and a lifetime's
messing about with electrical installations,

Should hardly be hindsight, then. After my first electrical shock at a
tender age I realised it's dangerous stuff and not to be messed with. I'm
genuinely surprised you're still here to post if this is your normal way
of working.

this is the first time that's happened to me and although your advice is
absolutely correct, worth giving and will I assure you be followed in
future, I note with interest that none of those whom I hoped would
answer my original post felt it necessary to comment on my possible
rashness - one could read in that, that they would have done the same.

I'd be very surprised if they did. Only idiots work on live mains circuits
- unless there is no option.

Otherwise, thanks guys - the topic will be 'discussed' therefore,
rather than 'strongly advised'

You also have to remember that lots read this group perhaps without
contributing. So general advice on best practice is just that and not
necessarily aimed at an individual.

--
*If they arrest the Energizer Bunny, would they charge it with battery? *

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

In article ,
Andy Wade wrote:
I guess that if you do replace the whole consumer unit now you'd have to
follow the 17th edition and provide suitably divided RCD protection
for everything.

Interesting. Why are non 17th edition CUs so readily available if any
replacement must comply?

--
*We waste time, so you don't have to *

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

Dave Plowman (News) wrote:
In article ,
Andy Wade wrote:
I guess that if you do replace the whole consumer unit now you'd have to
follow the 17th edition and provide suitably divided RCD protection
for everything.

Interesting. Why are non 17th edition CUs so readily available if any
replacement must comply?

You can use them in compliant ways with RCBOs etc. There are also
circumstances where you still want non RCD protected ways. Having said
that, many people will carry on working to the older standards for a
while, and the retailers will be happy to clear old stock. There will
also be an ongoing desire to do like for like swaps on damaged kit etc.

--
Cheers,

John.

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

I was asked by a friend to investigate a seemingly faulty 20A DP
switch for a washing machine today.

In hindsight slightly unwisely, I unscrewed the switch and pulled it
forward to be rewarded with a flash, bang and the appropriate cloud of
noxious smoke ! Hey isn't it great when you get the pyrotecniks
rather than just something going dead.

Anyway my guess is that the line terminal had not been tightened
properly originally, had over heated, the plastic broken down and my
approach had resulted in the line terminal breaking free and coming in
contact with the earth lead.

The fuse in the CU did not rupture !!

The switch was replaced.

The question arises now is should I strongly advise my friend to have
his fuses CU replaced with a modern one; the emphasis is on the
'strongly' as my feeling is that despite a large flash/short as this
was, the fuse did not protect the system as an RCD or MCB would have
done. In fact an RCD would probably have tripped out long before I
was asked to look and would have given the protection that the house
should have (said having just has my own RCD trip and finding that it
was due to the oven fan becoming leaky).


Perhaps he should have his entire electrical system checked by a qualified
professional followed by having any recommendations carried out
professionally as well. It seems a classic example of why Part P was
introduced.

Dons tin hat and retires to bunker!

Peter Crosland

Just remember the old proverb I was taught as an apprentice " there are old
electricians and bold electricians but there are no old bold electricians"
Sam
"robgraham" wrote in message
...
On 1 Aug, 08:17, "Dave Plowman (News)" wrote:
In article
,
robgraham wrote:

I was asked by a friend to investigate a seemingly faulty 20A DP
switch for a washing machine today.
In hindsight slightly unwisely, I unscrewed the switch and pulled it
forward to be rewarded with a flash, bang and the appropriate cloud of
noxious smoke ! Hey isn't it great when you get the pyrotecniks
rather than just something going dead.

It's total madness starting to investigate a fault with the power switched
on - especially on a strange installation where you've no idea if even the
earthing is correctly done.

Most of these sort of faults can be sorted with a simple inspection -
loose wires etc - and you don't need the power on for that.

--
*Real women don't have hot flashes, they have power surges.

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

Yes Dave, and hindsight is a great instructor. At 66 and a lifetime's
messing about with electrical installations, this is the first time
that's happened to me and although your advice is absolutely correct,
worth giving and will I assure you be followed in future, I note with
interest that none of those whom I hoped would answer my original post
felt it necessary to comment on my possible rashness - one could read
in that, that they would have done the same.

Otherwise, thanks guys - the topic will be 'discussed' therefore,
rather than 'strongly advised'

Rob

On Aug 1, 1:13*am, John Rumm wrote:
wrote:
Rewirable fuses are still fully compliant for new installation. You'd
derive very little safety benefit from adding MCBs. The reason the
fuses didnt pop is that any trip device takes a cvertain amount of i
times t to blow, and the fault, while it may have looked impressive,
didnt draw enough i x t, and the fault blew itself open circuit first.
You may have been scared by this, but safetywise its pretty much a non-
issue.

While this is true, there are two caveats worth mentioning: If the
cables are the older style PVC with only a 1mm^2 CPC (modern cable has
1.5mm^2) then it is worth moving away from rewireable fuses since the
protection will be marginal or insufficient in many cases.

1mm2 T&E CPC will not have any difficulty at all blowing rewirable
fuses. Its a long way from marginal. What can be marginal is its
compliance with disconnect times for new wiring regulations - but
thats nowhere near enough of an issue to prompt a CU replacment for
99% of the population.


If the power
(i.e. socket) circuits currently have no RCD protection then again it is
worth introducing this, which realistically will also mean a CU swap.

Again, the benefit exists but is so small that only a miniscule
percentage of the population would consider it worthwhile to fit the
new CU. Almost no-one rewires their house every time a minor safety
advance comes along.


NT

"John Rumm" wrote in message
et...
Dave Plowman (News) wrote:
In article ,
Andy Wade wrote:
I guess that if you do replace the whole consumer unit now you'd have to
follow the 17th edition and provide suitably divided RCD protection for
everything.

Interesting. Why are non 17th edition CUs so readily available if any
replacement must comply?

You can use them in compliant ways with RCBOs etc.

Exactly. A true pro (ie a good DIYer) as opposed to a sparky would buy a CU
with a non RCD main switch and use RCBOs instead of MCBs.

The term "17th edition CU" should read "minimum allowed to meet the 17th
edition at the lowest cost possible CU"

Adam

ARWadworth coughed up some electrons that declared:


"John Rumm" wrote in message
et...
Dave Plowman (News) wrote:
In article ,
Andy Wade wrote:
I guess that if you do replace the whole consumer unit now you'd have
to follow the 17th edition and provide suitably divided RCD protection
for everything.

Interesting. Why are non 17th edition CUs so readily available if any
replacement must comply?

You can use them in compliant ways with RCBOs etc.

Exactly. A true pro (ie a good DIYer) as opposed to a sparky would buy a
CU with a non RCD main switch and use RCBOs instead of MCBs.

The term "17th edition CU" should read "minimum allowed to meet the 17th
edition at the lowest cost possible CU"

Adam

And a true pervert would put in an industrial Type B 20 way SPSN board
filled with double pole RCBO's ;-

A real man, of course, has 3 phase...

Cheers

Tim

PS - I was seriously lusting after MEM's 8-way Type A board (well, 2,
stacked) with SP+SN busbar and matching RCBOs.

Until I priced it...

On Fri, 01 Aug 2008 21:44:36 +0100, wrote:

On 1 Aug,
Andy Wade wrote:


If the CU in question is the Wylex standard type, or one of its clones,
a worthwhile low-cost upgrade is to replace the rewireable fuses and
fuse carriers with HRC cartridge fuses:
http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Wylex_Standard_Carriers/index.html

Or even with these?
http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Wylex_Standard_Range/index.html

Haven't you replaced that CU yet? I thought I was the one that
procrastinated :-)

I bought a split load Wylex CU over a year ago (from Screwfix) and was
going to change it myself, but as I had the kitchen re-hashed a bit
later and would have to (well, you know!) go some sort of 'official'
route I got the leccy who did the kitchen wiring to change the CU.

It all saved going 17th edition... The supply to the fridge/freezer
(using the old cooker supply ) is now a non-RCD radial feed (labelled
as such).

--
Frank Erskine

wrote:
On Aug 1, 1:13 am, John Rumm wrote:
wrote:
Rewirable fuses are still fully compliant for new installation. You'd
derive very little safety benefit from adding MCBs. The reason the
fuses didnt pop is that any trip device takes a cvertain amount of i
times t to blow, and the fault, while it may have looked impressive,
didnt draw enough i x t, and the fault blew itself open circuit first.
You may have been scared by this, but safetywise its pretty much a non-
issue.
While this is true, there are two caveats worth mentioning: If the
cables are the older style PVC with only a 1mm^2 CPC (modern cable has
1.5mm^2) then it is worth moving away from rewireable fuses since the
protection will be marginal or insufficient in many cases.

1mm2 T&E CPC will not have any difficulty at all blowing rewirable
fuses. Its a long way from marginal. What can be marginal is its
compliance with disconnect times for new wiring regulations - but
thats nowhere near enough of an issue to prompt a CU replacment for
99% of the population.

If it can't achieve the required disconnect time, then it is at best
marginal. (and that's just the old 0.4 sec requirement).

As we have both said, the question of whether a BS 3036 semi-enclosed
fuse CU should be replaced is a broader question that needs to take
account of a number of factors. Compatibility with the installed wiring
is one factor.

If the power
(i.e. socket) circuits currently have no RCD protection then again it is
worth introducing this, which realistically will also mean a CU swap.

Again, the benefit exists but is so small that only a miniscule
percentage of the population would consider it worthwhile to fit the
new CU. Almost no-one rewires their house every time a minor safety
advance comes along.

No, I disagree strongly with this. There is no way you can call a RCD a
"minor safety advance". RCD protection makes a significant impact on the
survivability of electric shocks, and unlike nonsense like part P, the
the use of them has a big impact preventing death and serious injury as
a result of (ab)use of hand held appliances (which as we know is a
significant number, unlike those attributable to fixed wiring faults).



--
Cheers,

John.

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

John Rumm wrote:

wrote:

Rewirable fuses are still fully compliant for new installation. You'd
derive very little safety benefit from adding MCBs. The reason the
fuses didnt pop is that any trip device takes a cvertain amount of i
times t to blow, and the fault, while it may have looked impressive,
didnt draw enough i x t, and the fault blew itself open circuit first.
You may have been scared by this, but safetywise its pretty much a non-
issue.

While this is true, there are two caveats worth mentioning: If the
cables are the older style PVC with only a 1mm^2 CPC (modern cable has
1.5mm^2) then it is worth moving away from rewireable fuses since the
protection will be marginal or insufficient in many cases. If the power
(i.e. socket) circuits currently have no RCD protection then again it is
worth introducing this, which realistically will also mean a CU swap.

Are any figures available that show injury and/or deaths rates are
less under the new regime (in this case an RCD CU) than the old (a
fused CU)?

A casual reading of the group suggests that there are a number
potential benefits from the technical advances in going from the
former to the other latter - but how does it work out in practice?

In article ,
Tim S writes:

And a true pervert would put in an industrial Type B 20 way SPSN board
filled with double pole RCBO's ;-

A real man, of course, has 3 phase...

Cheers

Tim

PS - I was seriously lusting after MEM's 8-way Type A board (well, 2,
stacked) with SP+SN busbar and matching RCBOs.

Until I priced it...

Well, I went for the MEM (now Eaton) AM industrial range for
home...
http://www.cucumber.demon.co.uk/cu1.jpg
http://www.cucumber.demon.co.uk/cu2.jpg

It's very nice to use compared to cheap plastic ones, and
in the case of DIY, that's where you can spend the money
you saved by DIYing it, although I think you're looking
at around £320 for what's in that picture. More bits were
added just afterwards which I had to wait for as they
were ordered from MEM. This was the 3rd MEM AM range CU
I fitted in different places.

(The extra box above is to extend the wires which weren't
long enough after removing the old CU.)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Andrew Gabriel coughed up some electrons that declared:

In article ,
Tim S writes:

And a true pervert would put in an industrial Type B 20 way SPSN board
filled with double pole RCBO's ;-

A real man, of course, has 3 phase...

Cheers

Tim

PS - I was seriously lusting after MEM's 8-way Type A board (well, 2,
stacked) with SP+SN busbar and matching RCBOs.

Until I priced it...

Well, I went for the MEM (now Eaton) AM industrial range for
home...
http://www.cucumber.demon.co.uk/cu1.jpg
http://www.cucumber.demon.co.uk/cu2.jpg

It's very nice to use compared to cheap plastic ones, and
in the case of DIY, that's where you can spend the money
you saved by DIYing it, although I think you're looking
at around £320 for what's in that picture. More bits were
added just afterwards which I had to wait for as they
were ordered from MEM. This was the 3rd MEM AM range CU
I fitted in different places.

(The extra box above is to extend the wires which weren't
long enough after removing the old CU.)


That's a work of art Andrew. Where did you get your kit from? The only
online supplier of MEM I can find is www.kempstoncontrols.co.uk and even
the ready assembled RCBO's (SP/1 module) are 66+VAT. I suspect you paid
less?

I priced up the 2x AM8D board (L+N busbar, no need for neutral tails - then
one I meant above) and 11 DP RCBOs and it's that that came to 1400 ish inc
VAT. The DP MCB+MR30 field-fittable RCD module came to about
78+VAT/circuit. That's what killed it for me.

It was pushing me back towards Hager who aren't bad but the RCBOs are way
cheaper, ditto Crabtree.

On an aside, I assume you had to go with Type C overload RCBOs? Any issues
with these over Type B?

I'm aware of the argument that even on TN-S where Type C may not provide
sufficient protection against indirect contact that the RCD nullifies this
by itself providing the required disconnection time for an L-E fault, but
nevertheless...

Cheers

Tim

On 2008-08-02 10:00:06 +0100, (Andrew
Gabriel) said:

In article ,
Tim S writes:

And a true pervert would put in an industrial Type B 20 way SPSN board
filled with double pole RCBO's ;-

A real man, of course, has 3 phase...

Cheers

Tim

PS - I was seriously lusting after MEM's 8-way Type A board (well, 2,
stacked) with SP+SN busbar and matching RCBOs.

Until I priced it...

Well, I went for the MEM (now Eaton) AM industrial range for
home...
http://www.cucumber.demon.co.uk/cu1.jpg
http://www.cucumber.demon.co.uk/cu2.jpg

It's very nice to use compared to cheap plastic ones, and
in the case of DIY, that's where you can spend the money
you saved by DIYing it, although I think you're looking
at around £320 for what's in that picture. More bits were
added just afterwards which I had to wait for as they
were ordered from MEM. This was the 3rd MEM AM range CU
I fitted in different places.

(The extra box above is to extend the wires which weren't
long enough after removing the old CU.)

Nice job. Some questions.

What are the devices above the breakers on the right or is it that
these are RCBOs as opposed to MCBs on the left?

Do the tails come in to the back?

What are the small grey wires at the bottom? Part of the automation system?

Andy Hall coughed up some electrons that declared:

On 2008-08-02 10:00:06 +0100, (Andrew
Gabriel) said:

In article ,
Tim S writes:

And a true pervert would put in an industrial Type B 20 way SPSN board
filled with double pole RCBO's ;-

A real man, of course, has 3 phase...

Cheers

Tim

PS - I was seriously lusting after MEM's 8-way Type A board (well, 2,
stacked) with SP+SN busbar and matching RCBOs.

Until I priced it...

Well, I went for the MEM (now Eaton) AM industrial range for
home...
http://www.cucumber.demon.co.uk/cu1.jpg
http://www.cucumber.demon.co.uk/cu2.jpg

It's very nice to use compared to cheap plastic ones, and
in the case of DIY, that's where you can spend the money
you saved by DIYing it, although I think you're looking
at around £320 for what's in that picture. More bits were
added just afterwards which I had to wait for as they
were ordered from MEM. This was the 3rd MEM AM range CU
I fitted in different places.

(The extra box above is to extend the wires which weren't
long enough after removing the old CU.)

Nice job. Some questions.

What are the devices above the breakers on the right or is it that
these are RCBOs as opposed to MCBs on the left?

Yes.

Do the tails come in to the back?

What are the small grey wires at the bottom? Part of the automation
system?

Functional earths, for the test button on the RCBOs.

Cheers

Tim

In article ,
Tim S writes:
Andrew Gabriel coughed up some electrons that declared:
Well, I went for the MEM (now Eaton) AM industrial range for
home...
http://www.cucumber.demon.co.uk/cu1.jpg
http://www.cucumber.demon.co.uk/cu2.jpg

It's very nice to use compared to cheap plastic ones, and
in the case of DIY, that's where you can spend the money
you saved by DIYing it, although I think you're looking
at around £320 for what's in that picture. More bits were
added just afterwards which I had to wait for as they
were ordered from MEM. This was the 3rd MEM AM range CU
I fitted in different places.

(The extra box above is to extend the wires which weren't
long enough after removing the old CU.)


That's a work of art Andrew. Where did you get your kit from? The only
online supplier of MEM I can find is www.kempstoncontrols.co.uk and even
the ready assembled RCBO's (SP/1 module) are 66+VAT. I suspect you paid
less?

I don't believe building trades people use on-line ordering
much. I bought them from trade counters; IIRC, a combination of
ERD (who stocked most things but wouldn't order anything else
except in box quantities), and Gibbs & Dandy (who didn't stock
much of the range, but would order anything even singularly).

The RCBOs you see there are all made up by me from MCBs and
RCBO pods. The RCBO pods were under £50 each (might have been
more if I was buying just one), and the MCBs well under £10
each (I tend to ignore the price of those).

I priced up the 2x AM8D board (L+N busbar, no need for neutral tails - then
one I meant above) and 11 DP RCBOs and it's that that came to 1400 ish inc
VAT. The DP MCB+MR30 field-fittable RCD module came to about
78+VAT/circuit. That's what killed it for me.

It was pushing me back towards Hager who aren't bad but the RCBOs are way
cheaper, ditto Crabtree.

On an aside, I assume you had to go with Type C overload RCBOs? Any issues
with these over Type B?

Because I made them up from separate MCBs and RCBO pods, all
the RCBOs in that picture are actually Type B. There would have
been no issue with using Type C because by definition they're
all RCD protected. If they weren't RCD protected, you'd have
to double-check the earth fault loop impedance against more
stringent values for Type C to ensure they still meet disconnect
times.

The 6A lighting MCBs are all Type C, as is a 20A radial for things
I didn't want RCD protected.

I'm aware of the argument that even on TN-S where Type C may not provide
sufficient protection against indirect contact that the RCD nullifies this
by itself providing the required disconnection time for an L-E fault, but
nevertheless...

For the outdoor sockets circuit, which is a 20A radial Type C,
I used a C20A 10mA RCBO prebuilt. That had to be ordered and didn't
arrive until after I took the photo, but it looks exactly the
same as the ones I assembled myself. At £60 IIRC, it was the most
expensive component. I went for a Type C there because I could
imagine it being used for large motor appliances. I went for 10mA
because it's generally only used for one or two appliances so
cumulative appliance leakage isn't an issue, and earth leakage paths
through you outdoors can be subject to additional external resistances
which might serve to limit the current below 30mA. That circuit is
also TT, where as the rest are all TN-C-S.

Also bear in mind my prices are ~5 years ago.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Tim S writes:
Andy Hall coughed up some electrons that declared:

What are the devices above the breakers on the right or is it that
these are RCBOs as opposed to MCBs on the left?

Yes.

That reminds me -- the RCBOs do get warm, as they contain
functional electronics which runs continuously[1]. I rearranged
them slightly after that picture was taken so they weren't
all next to each other, so they would stay a bit cooler,
not that I have any reason to think that might be a problem.
Typical life of electronic components does halve which each
10C temperature rise though.

There are also requirements on not putting the more sensitive
RCBOs next to high current circuits (40A or above, IIRC) due
to magnetic interference.

[1] I wonder if anyone's worked out how many more power
stations we'll need to bring all installations up to 17th
Ed regs (or later) over the next 30 years or so?

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 2008-08-02 11:51:18 +0100, (Andrew
Gabriel) said:

In article ,
Tim S writes:
Andy Hall coughed up some electrons that declared:

What are the devices above the breakers on the right or is it that
these are RCBOs as opposed to MCBs on the left?

Yes.

That reminds me -- the RCBOs do get warm, as they contain
functional electronics which runs continuously[1].

Is this because of their RCBO properties or through dealing with 10mA
detection?



I rearranged
them slightly after that picture was taken so they weren't
all next to each other, so they would stay a bit cooler,
not that I have any reason to think that might be a problem.
Typical life of electronic components does halve which each
10C temperature rise though.

There are also requirements on not putting the more sensitive
RCBOs next to high current circuits (40A or above, IIRC) due
to magnetic interference.

Spacers for this or changing the order?



[1] I wonder if anyone's worked out how many more power
stations we'll need to bring all installations up to 17th
Ed regs (or later) over the next 30 years or so?

I suppose if the RCBOs are getting warm to the touch, they are using a
couple of watts each?

In article 489430d5@qaanaaq,
Andy Hall writes:

Do the tails come in to the back?

Yes. The position where the tails came out of the wall was
a significant influence on the positioning of the CU. I did
move that a couple of inches to make it all line up vertically,
which wasn't difficult on a thermal block wall where you can
almost use your finger nails to scrape out a larger hole.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Andrew Gabriel coughed up some electrons that declared:

In article ,
Tim S writes:
Andrew Gabriel coughed up some electrons that declared:
Well, I went for the MEM (now Eaton) AM industrial range for
home...
http://www.cucumber.demon.co.uk/cu1.jpg
http://www.cucumber.demon.co.uk/cu2.jpg

It's very nice to use compared to cheap plastic ones, and
in the case of DIY, that's where you can spend the money
you saved by DIYing it, although I think you're looking
at around £320 for what's in that picture. More bits were
added just afterwards which I had to wait for as they
were ordered from MEM. This was the 3rd MEM AM range CU
I fitted in different places.

(The extra box above is to extend the wires which weren't
long enough after removing the old CU.)


That's a work of art Andrew. Where did you get your kit from? The only
online supplier of MEM I can find is www.kempstoncontrols.co.uk and even
the ready assembled RCBO's (SP/1 module) are 66+VAT. I suspect you paid
less?

I don't believe building trades people use on-line ordering
much.

True enough - just price gauging at the moment. My local TLC are very
helpful, but not very good at getting unusual kit (eg a Wylex REC2 DP 100A
isolator had them flummoxed, but it's the optimum device for running tails
in an out of as it's designed to do exactly that, and the load terminals
are accessible by a separate cover so it's possible to work on a live
but "off" one safely). MEM are "unusual" for them too. I'll give them a
chance to source because they are very helpful, but I don't hold too much
hope.

I bought them from trade counters; IIRC, a combination of
ERD (who stocked most things but wouldn't order anything else
except in box quantities), and Gibbs & Dandy (who didn't stock
much of the range, but would order anything even singularly).

Is that ERD in Luton? Found Gibbs and Dandy - branch in Slough. I'm near T
Wells in Kent so it's not a million miles and worth knowing they can source
stuff. Thanks for that.

The RCBOs you see there are all made up by me from MCBs and
RCBO pods. The RCBO pods were under £50 each (might have been
more if I was buying just one), and the MCBs well under £10
each (I tend to ignore the price of those).

Ah. Just looked at memonline.com harder. I found the RCD for DP MCBs, the
MR30. Just re-read it and the MR30 pod seems to do SP too - is that the one
you used?

That was part of the attraction with MEM - being able to stick in Type B and
Type C according to the requirements of each circuit without having to
fudge the issue.

I priced up the 2x AM8D board (L+N busbar, no need for neutral tails -
then one I meant above) and 11 DP RCBOs and it's that that came to 1400
ish inc VAT. The DP MCB+MR30 field-fittable RCD module came to about
78+VAT/circuit. That's what killed it for me.

It was pushing me back towards Hager who aren't bad but the RCBOs are way
cheaper, ditto Crabtree.

On an aside, I assume you had to go with Type C overload RCBOs? Any
issues with these over Type B?

Because I made them up from separate MCBs and RCBO pods, all
the RCBOs in that picture are actually Type B. There would have
been no issue with using Type C because by definition they're
all RCD protected. If they weren't RCD protected, you'd have
to double-check the earth fault loop impedance against more
stringent values for Type C to ensure they still meet disconnect
times.

The 6A lighting MCBs are all Type C, as is a 20A radial for things
I didn't want RCD protected.

I'm aware of the argument that even on TN-S where Type C may not provide
sufficient protection against indirect contact that the RCD nullifies
this by itself providing the required disconnection time for an L-E
fault, but nevertheless...

For the outdoor sockets circuit, which is a 20A radial Type C,
I used a C20A 10mA RCBO prebuilt. That had to be ordered and didn't
arrive until after I took the photo, but it looks exactly the
same as the ones I assembled myself. At £60 IIRC, it was the most
expensive component. I went for a Type C there because I could
imagine it being used for large motor appliances. I went for 10mA
because it's generally only used for one or two appliances so
cumulative appliance leakage isn't an issue, and earth leakage paths
through you outdoors can be subject to additional external resistances
which might serve to limit the current below 30mA. That circuit is
also TT, where as the rest are all TN-C-S.

Also bear in mind my prices are ~5 years ago.


Cheers

Tim

In article 48943e19@qaanaaq,
Andy Hall writes:
On 2008-08-02 11:51:18 +0100, (Andrew
Gabriel) said:

In article ,
Tim S writes:
Andy Hall coughed up some electrons that declared:

What are the devices above the breakers on the right or is it that
these are RCBOs as opposed to MCBs on the left?

Yes.

That reminds me -- the RCBOs do get warm, as they contain
functional electronics which runs continuously[1].

Is this because of their RCBO properties or through dealing with 10mA
detection?

It applies to all RCDs. The 10mA rating doesn't make any difference.

I rearranged
them slightly after that picture was taken so they weren't
all next to each other, so they would stay a bit cooler,
not that I have any reason to think that might be a problem.
Typical life of electronic components does halve which each
10C temperature rise though.

There are also requirements on not putting the more sensitive
RCBOs next to high current circuits (40A or above, IIRC) due
to magnetic interference.

Spacers for this or changing the order?

I changed the order.

The spacers were only temporary because I didn't have all the
components when the photo was taken. I always fill a CU with
MCBs even if they aren't all used. They're cheap, and they
might no longer be easily obtainable when you want some more
later on. (I got caught out with this once in the past when
MK stopped doing their original single way RCBOs.)

[1] I wonder if anyone's worked out how many more power
stations we'll need to bring all installations up to 17th
Ed regs (or later) over the next 30 years or so?

I suppose if the RCBOs are getting warm to the touch, they are using a
couple of watts each?

Probably less than a watt, but when squashed together, there's
not a lot of surface area to dissipate that from the middle
ones.

I have a couple of spares -- I could rig something up on the
bench to measure the power consumption of the RCBOs.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Tim S writes:
Andrew Gabriel coughed up some electrons that declared:

I bought them from trade counters; IIRC, a combination of
ERD (who stocked most things but wouldn't order anything else
except in box quantities), and Gibbs & Dandy (who didn't stock
much of the range, but would order anything even singularly).

Is that ERD in Luton? Found Gibbs and Dandy - branch in Slough. I'm near T
Wells in Kent so it's not a million miles and worth knowing they can source
stuff. Thanks for that.

I thought ERD were all over the place (at least in the South East - I
think they are also known as Edmundson Electrical), but strangely enough,
it was one of the Luton ones, the one on North Luton Industrial Estate.
The other Luton one (near Screwfix) specialises in other makes, but has
some more common MEM bits. It was also the Luton Gibbs & Dandy.

The RCBOs you see there are all made up by me from MCBs and
RCBO pods. The RCBO pods were under £50 each (might have been
more if I was buying just one), and the MCBs well under £10
each (I tend to ignore the price of those).

Ah. Just looked at memonline.com harder. I found the RCD for DP MCBs, the
MR30. Just re-read it and the MR30 pod seems to do SP too - is that the one
you used?

Yes.

Be careful with the MCBs though. MEM do more than one range and it's
easy to get them mixed up. One is for these industrial boards (and
has a 10kA breaking capacity) and the other range is for domestic
boards and has a lower breaking capacity (probably 6kA). I don't
think the pods are intended to fit to the domestic breakers, but I
never tried.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Andrew Gabriel coughed up some electrons that declared:

In article ,
Tim S writes:
Andrew Gabriel coughed up some electrons that declared:

I bought them from trade counters; IIRC, a combination of
ERD (who stocked most things but wouldn't order anything else
except in box quantities), and Gibbs & Dandy (who didn't stock
much of the range, but would order anything even singularly).

Is that ERD in Luton? Found Gibbs and Dandy - branch in Slough. I'm near
T Wells in Kent so it's not a million miles and worth knowing they can
source stuff. Thanks for that.

I thought ERD were all over the place (at least in the South East - I
think they are also known as Edmundson Electrical), but strangely enough,
it was one of the Luton ones, the one on North Luton Industrial Estate.

Well, nadger me doobries - now I have their full name, have located branches
in T Wells and Tonbridge. Never noticed them so they must be raund the back
of all the places I normal frequent. Thanks - will look in on them.

The other Luton one (near Screwfix) specialises in other makes, but has
some more common MEM bits. It was also the Luton Gibbs & Dandy.

The RCBOs you see there are all made up by me from MCBs and
RCBO pods. The RCBO pods were under £50 each (might have been
more if I was buying just one), and the MCBs well under £10
each (I tend to ignore the price of those).

Ah. Just looked at memonline.com harder. I found the RCD for DP MCBs, the
MR30. Just re-read it and the MR30 pod seems to do SP too - is that the
one you used?

Yes.

Be careful with the MCBs though. MEM do more than one range and it's
easy to get them mixed up. One is for these industrial boards (and
has a 10kA breaking capacity) and the other range is for domestic
boards and has a lower breaking capacity (probably 6kA). I don't
think the pods are intended to fit to the domestic breakers, but I
never tried.


Cheers - I noticed that too.

Thanks

Tim

On Aug 2, 4:00*am, John Rumm wrote:
wrote:
On Aug 1, 1:13 am, John Rumm wrote:
wrote:
Rewirable fuses are still fully compliant for new installation. You'd
derive very little safety benefit from adding MCBs. The reason the
fuses didnt pop is that any trip device takes a cvertain amount of i
times t to blow, and the fault, while it may have looked impressive,
didnt draw enough i x t, and the fault blew itself open circuit first..
You may have been scared by this, but safetywise its pretty much a non-
issue.
While this is true, there are two caveats worth mentioning: If the
cables are the older style PVC with only a 1mm^2 CPC (modern cable has
1.5mm^2) then it is worth moving away from rewireable fuses since the
protection will be marginal or insufficient in many cases.

1mm2 T&E CPC will not have any difficulty at all blowing rewirable
fuses. Its a long way from marginal. What can be marginal is its
compliance with disconnect times for new wiring regulations - but
thats nowhere near enough of an issue to prompt a CU replacment for
99% of the population.

If it can't achieve the required disconnect time, then it is at best
marginal. (and that's just the old 0.4 sec requirement).

There is no required disconnect time for existing installations.
Required times apply to new wiring. Whether a domestic socket circuit
takes 0.45s or 0.35s to fuse makes absolutely blank all difference to
real world death rates. And /that/ is whats relevant here, nowt else.


As we have both said, the question of whether a BS 3036 semi-enclosed
fuse CU should be replaced is a broader question that needs to take
account of a number of factors. Compatibility with the installed wiring
is one factor.

I think the biggest factor is the ratio of safety benefit to expense.
Since the safety factor is about zero, and there are mass killers in
the average house, twiddling with the fusebox is both pointless and
counterproductive.


If the power
(i.e. socket) circuits currently have no RCD protection then again it is
worth introducing this, which realistically will also mean a CU swap.

Again, the benefit exists but is so small that only a miniscule
percentage of the population would consider it worthwhile to fit the
new CU. Almost no-one rewires their house every time a minor safety
advance comes along.

No, I disagree strongly with this. There is no way you can call a RCD a
"minor safety advance". RCD protection makes a significant impact on the
survivability of electric shocks, and unlike nonsense like part P, the
the use of them has a big impact preventing death and serious injury as
a result of (ab)use of hand held appliances (which as we know is a
significant number, unlike those attributable to fixed wiring faults).

I agree theyre much more significant than fuses/mcbs, but. Twenty
something deaths a year, of which some are down to appliance abuse.
RCDs would indeed stop some of those deaths. But they also encourage
people to do things they never would have before, causing more of the
situations, and they cause loss of sair lighting, loss of lighting in
fires etc, which we know kills people. So the real world safety cost
or benefit is anything but clear. We simply don't have the figures
yet.

But once again... if you want to save lives in the home, there are
much greater results to be had by spending much less on the real risk
issues.


NT

Terry Fields wrote:
John Rumm wrote:

wrote:

Rewirable fuses are still fully compliant for new installation. You'd
derive very little safety benefit from adding MCBs. The reason the
fuses didnt pop is that any trip device takes a cvertain amount of i
times t to blow, and the fault, while it may have looked impressive,
didnt draw enough i x t, and the fault blew itself open circuit first.
You may have been scared by this, but safetywise its pretty much a non-
issue.
While this is true, there are two caveats worth mentioning: If the
cables are the older style PVC with only a 1mm^2 CPC (modern cable has
1.5mm^2) then it is worth moving away from rewireable fuses since the
protection will be marginal or insufficient in many cases. If the power
(i.e. socket) circuits currently have no RCD protection then again it is
worth introducing this, which realistically will also mean a CU swap.

Are any figures available that show injury and/or deaths rates are
less under the new regime (in this case an RCD CU) than the old (a
fused CU)?

Its a good question, and I don't know how easy it would be to get
figures in the exact form required... Until recently[1] deaths from
electrocution have fallen year on year in absolute terms for quite a
number of years, even though usage of appliances has risen. This won't
be attributable to just one improvement in safety, but a collective
effect of which RCDs have been a part quite a number of years now.

[1] In the last couple of years this trend seems to be showing signs of
reversing - strangely coincident with the introduction of Part P

A casual reading of the group suggests that there are a number
potential benefits from the technical advances in going from the
former to the other latter - but how does it work out in practice?

Not sure I follow the question - do you mean what will be the change in
user experience? or the actual process of making the change?


--
Cheers,

John.

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

In article
,
wrote:
If it can't achieve the required disconnect time, then it is at best
marginal. (and that's just the old 0.4 sec requirement).

There is no required disconnect time for existing installations.
Required times apply to new wiring. Whether a domestic socket circuit
takes 0.45s or 0.35s to fuse makes absolutely blank all difference to
real world death rates. And /that/ is whats relevant here, nowt else.

One thing with fuses is it's all too easy to fit a larger one to an
overloaded circuit - I've seen this many times. Not many who do this sort
of thing would know how to change an MCB.

--
*What do little birdies see when they get knocked unconscious? *

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

wrote:

1mm2 T&E CPC will not have any difficulty at all blowing rewirable
fuses. Its a long way from marginal.

That's not the case at all if we're talking about the 30 A rewireable
fuse (BS 3036). If you superimpose the adiabatic line for a 1 mm^2
conductor with a k value of 115 over the relevant fuse characteristic
you discover that the former lies wholly below the latter. In other
words the fuse can't be relied on to protect the 1 mm^2 CPC at any fault
current. Hence unfused spurs in ring circuits in many old installations
were never compliant in respect of thermal protection of the CPC.
That's why the cable standard (BS 6004) was changed in 1984 to require a
1.5 mm^2 CPC.

Common sense might also hint of a problem in the above case: the fuse
wire is only about 10 thou' smaller than the conductor it's trying to
protect.

What can be marginal is its compliance with disconnect times for new
wiring regulations

That's more a general design matter (coordination), rather than
something related specifically to the fuse or cable. Of course the 0.4
s disconnection time requirement hasn't changed for TN systems (but does
now have wider scope). What has changed is that the old 'alternative
method' (limitation of fault voltage drop) has gone from the 17th ed.,
replaced by a requirement for local supplementary bonding where 0.4 s
disconnection can't be achieved. 30 A rings protected by a rewireable
fuse in TN-S earthed systems do rely on the alternative method if the Ze
value is high, and hence might not comply with the 17th ed.

In general you can say that although rewireable fuses are still
permitted it's now harder than before to ensure full compliance when
using them. Standard circuits - per Table 7.1 in the previous OSGs -
are not necessarily compliant with the 17th ed. It will be interesting
to see how this table looks in the new edition, when it finally comes out.

--
Andy

wrote:
On Aug 2, 4:00 am, John Rumm wrote:
wrote:
On Aug 1, 1:13 am, John Rumm wrote:
wrote:
Rewirable fuses are still fully compliant for new installation. You'd
derive very little safety benefit from adding MCBs. The reason the
fuses didnt pop is that any trip device takes a cvertain amount of i
times t to blow, and the fault, while it may have looked impressive,
didnt draw enough i x t, and the fault blew itself open circuit first.
You may have been scared by this, but safetywise its pretty much a non-
issue.
While this is true, there are two caveats worth mentioning: If the
cables are the older style PVC with only a 1mm^2 CPC (modern cable has
1.5mm^2) then it is worth moving away from rewireable fuses since the
protection will be marginal or insufficient in many cases.
1mm2 T&E CPC will not have any difficulty at all blowing rewirable
fuses. Its a long way from marginal. What can be marginal is its
compliance with disconnect times for new wiring regulations - but
thats nowhere near enough of an issue to prompt a CU replacment for
99% of the population.
If it can't achieve the required disconnect time, then it is at best
marginal. (and that's just the old 0.4 sec requirement).

There is no required disconnect time for existing installations.
Required times apply to new wiring. Whether a domestic socket circuit
takes 0.45s or 0.35s to fuse makes absolutely blank all difference to
real world death rates. And /that/ is whats relevant here, nowt else.

Disconnect times have been specified in the regs for many years. The
difference of .1 sec etc may not have a huge impact, however when
disconnect times start creeping up into the multiple of seconds then the
risks do become more significant (not only due to prolonged exposure to
high voltage earthed metalwork, but also that the CPC in the cable will
fail, or the cable sustain damage before the fuse operates).

As we have both said, the question of whether a BS 3036 semi-enclosed
fuse CU should be replaced is a broader question that needs to take
account of a number of factors. Compatibility with the installed wiring
is one factor.

I think the biggest factor is the ratio of safety benefit to expense.
Since the safety factor is about zero, and there are mass killers in
the average house, twiddling with the fusebox is both pointless and
counterproductive.

The improving stats for safety of electrical installations in general
would seem to disprove that the safety factor is zero, also blanket
statements about the pros and cons of changing a CU are not really much
use since they concentrate on too small a part of the picture. There
will be times when swapping out a working BS3036 CU for a modern one
will bring no improvement in safety, and there are times when it will
bring about a dramatic and significant improvement.

If the power
(i.e. socket) circuits currently have no RCD protection then again it is
worth introducing this, which realistically will also mean a CU swap.
Again, the benefit exists but is so small that only a miniscule
percentage of the population would consider it worthwhile to fit the
new CU. Almost no-one rewires their house every time a minor safety
advance comes along.

No, I disagree strongly with this. There is no way you can call a RCD a
"minor safety advance". RCD protection makes a significant impact on the
survivability of electric shocks, and unlike nonsense like part P, the
the use of them has a big impact preventing death and serious injury as
a result of (ab)use of hand held appliances (which as we know is a
significant number, unlike those attributable to fixed wiring faults).

I agree theyre much more significant than fuses/mcbs, but. Twenty
something deaths a year, of which some are down to appliance abuse.

IIUC the = 20 per year are those attributable to fixed wiring I
understand, not the those from appliance abuse.

RCDs would indeed stop some of those deaths. But they also encourage
people to do things they never would have before, causing more of the

This is probably true - but only in a very small subset of cases where
the user of the appliance has a good technical appreciation for what the
RCD is and does. IME the vast majority of people have little grasp of
what is in the CU or what it does, other than there being lots of
"little switches" that they need to reset from time to time, and never
necessarily even associate the need to reset them with any other event.

So I would be very surprised if having a CU with RCDs prefitted is going
to influence behaviour for many people. (you only need look at the group
of accidents that occur with extension leads in the garden - its not
usually mowing over it that causes the shock, its the dopey pillock
picking up the severed ends to look at them!)

situations, and they cause loss of sair lighting, loss of lighting in
fires etc, which we know kills people. So the real world safety cost
or benefit is anything but clear. We simply don't have the figures
yet.

Well this has been known about for some time (most of the reign of the
16th edition) and remedies put in place to address the problem.

But once again... if you want to save lives in the home, there are
much greater results to be had by spending much less on the real risk
issues.

Again, it depends on circumstances. In situations where students are
likely to overload circuits in their lodging house, and replace fuses
with tinfoil etc, or where there are lots of ankle biters roaming about
trying to push bits of metal into sockets to see what happens, you have
a real risk that needs addressing as a mater of urgency. In other cases
where a couple of adults share a flat, never need to mow a lawn, and do
nothing more exotic than plug in the TV and the phone charger there is
relatively little risk with 3036 fuses and no RCD.


--
Cheers,

John.

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In article ,
says...


One thing with fuses is it's all too easy to fit a larger one to an
overloaded circuit - I've seen this many times. Not many who do this sort
of thing would know how to change an MCB.


Yes, when I moved into this place some years ago each fuse was wired
with fuse wire that went from one screw, round the other and back to the
first...

Our place, when we lived in in France, had cartridge fuses and,
following that experience, I now much prefer rewireable ones.
--
John W
To mail me replace the obvious with co.uk twice

On Sat, 2 Aug 2008 20:04:11 +0100, John W. wrote:

Yes, when I moved into this place some years ago each fuse was wired
with fuse wire that went from one screw, round the other and back to the
first...

Our place, when we lived in in France, had cartridge fuses and,
following that experience, I now much prefer rewireable ones.

I always find it difficult soldering the fuse wire to the cartridge ends...

Geo

Andy Hall wrote:

What are the small grey wires at the bottom? Part of the automation
system?

MK RCBOs have a dedicated earth connection on each device. Not so
commonly found on other brands...


--
Cheers,

John.

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

John Rumm wrote:
Andy Hall wrote:

What are the small grey wires at the bottom? Part of the automation
system?

MK RCBOs have a dedicated earth connection on each device. Not so
commonly found on other brands...

Sorry, brain fart, make that Mem! (MK and Hager are similar though IIRC)

--
Cheers,

John.

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