Abus Granite 54 lock problem

On Fri, 15 Oct 2004 11:09:51 +0100 someone who may be David Martin
<[email hidden]> wrote this:-

Quoted message said:

Residual current device.. Detects if you have cut through the cable and are
electrocuting yourself.

Detects if the currents in the live and neutral wires are not the
same (for single phase wiring). If they are not the same you may
have cut through the cable and if this is the case you may be in the
process of being electrocuted.

Quoted message said:

A good thing to have on all electrical stuff in
hazardous environs (eg garden, shed etc.

As you are in Dundee then it is the law for all new installations in
sheds and gardens (and has been for at least a decade).

--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me by using the RIP Act 2000.

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Colin Blackburn said:

Quoted message said:

Bic is a popular make of disposable cigarette lighters, ballpoint pens,
pencils and disposable razors[...]

...and canoes.

Call those canoes?

http://www.bicsportkayaks.com

They are a poor excuse for sit-on kayaks.
Where's the carbon fibre? Kevlar? epoxy?

--
Eiron.

Victor said:

I was prepared for a long bloody battle. I even bought 3 spare cutting
disks. Got a refund on those puppies 🙂 Guess I was lucky that an electical
outlet was within reasonable distance, thus avoiding the petrol saw job.

And for the budding bike thieves out there, did anyone at all show any
interest in the fact that you were cutting a bike lock off with an angle
grinder for ten minutes?

Tony

David Hansen [email hidden] opined the following...
<snip>
While I don't doubt your experience in these matters there are a few
considerations.

I can fit an RCD which will trip in under 10ms in response to a 10mA
difference between the live and neutral terminals. This is classed as
shock protection (As apposed to life protection).

I cannot fit a fuse that will provide the same level of protection
against a piece of equipment with a normal operating current of 2A let
alone 20A.

An interesting piece of research (Interesting as much due to its
source!) is that it only 300mA to stop the heart and 30mA for long
enough (Less than a second IIRC) is enough to achieve this.

Despite this my fuse board is fitted with fuses because I live in a
rented property and have no control over such things. I recently had a
narrow escape (Complete stupidity on my behalf. I desire no sympathy!)
when I sucessfully shorted live to earth using a table knife while
attempting to open a control panel in my fridge. The fridge went dark
and quiet and the end of my knife went black and lost a chunk out of the
tip. An RCD will protect a moron <stands up, bows, sits down!> against a
greater range of common stupidities than a fuse.

Jon

On Sat, 16 Oct 2004 00:59:27 +0100 someone who may be Jon Senior
<jon_AT_restlesslemon_DOTco_DOT_uk> wrote this:-

Quoted message said:

I can fit an RCD which will trip in under 10ms in response to a 10mA
difference between the live and neutral terminals.

Quoted message said:

I cannot fit a fuse that will provide the same level of protection
against a piece of equipment with a normal operating current of 2A let
alone 20A.

As I said before "they are not designed to perform the same
function". You appear to be assuming that they do perform the same
function.

Some people believe that an RCD will protect them against
electrocution. That is a very dangerous assumption, because an RCD
will only do so in specific circumstances. It is perfectly possible
to electrocute oneself while even the most sensitive RCD does
precisely nothing. A little knowledge can be very dangerous.

Quoted message said:

An interesting piece of research (Interesting as much due to its
source!) is that it only 300mA to stop the heart and 30mA for long
enough (Less than a second IIRC) is enough to achieve this.

One of the reasons standard domestic socket outlet circuits are
designed to disconnect in less than 0.4s if there is a fault is to
reduce the chances of electrocution. The device which does this is
the fuse you appear to dislike so much, or a miniature circuit
breaker and it usually operates far faster than 0.4s. A High
Breaking Capacity fuse will operate in rather less than a quarter of
a cycle, dramatically limiting the energy which is let through.

--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me by using the RIP Act 2000.

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David Hansen [email hidden] opined the following...

Quoted message said:

As I said before "they are not designed to perform the same
function". You appear to be assuming that they do perform the same
function.

I don't. My original post that you corrected was a mistype. However the
world in general (IEEE etc) seems to classify fuses as equipment
protection and RCDs as user protection. They may be on to something! ;-)

Quoted message said:

Some people believe that an RCD will protect them against
electrocution. That is a very dangerous assumption, because an RCD
will only do so in specific circumstances. It is perfectly possible
to electrocute oneself while even the most sensitive RCD does
precisely nothing. A little knowledge can be very dangerous.

The only circumstances where an RCD will not protect someone (That I can
think of) are where the person manages to become the path from live to
neutral while they are isolated from earth. I guess with some big rubber
boots and bad luck this could happen, but in most incidents involving
electrocution the victim forms a path to earth. In these incidents an
RCD will act at a much lower current than a fuse, limiting the damage.

An RCD should NOT be used on its own, but always combined with some form
of overcurrent protection such as a fuse or circuit breaker.

Quoted message said:

One of the reasons standard domestic socket outlet circuits are
designed to disconnect in less than 0.4s if there is a fault is to
reduce the chances of electrocution. The device which does this is
the fuse you appear to dislike so much, or a miniature circuit
breaker and it usually operates far faster than 0.4s. A High
Breaking Capacity fuse will operate in rather less than a quarter of
a cycle, dramatically limiting the energy which is let through.

You are talking 400ms and 3A, I'm talking 30ms and 30mA. While there are
circumstances in which a fuse will save you that an RCD wont they don't
really represent the "common" electrical incident.

I don't dislike fuses, but I don't view them as being as important to
saving lives as RCDs.

Jon

Jon

David Hansen said:

Some people believe that an RCD will protect them against
electrocution. That is a very dangerous assumption, because an RCD
will only do so in specific circumstances. It is perfectly possible
to electrocute oneself while even the most sensitive RCD does
precisely nothing. A little knowledge can be very dangerous.

Possible but difficult. The only situation I can think of off the top
of my head is if you held the live and neutral wires while relatively
insulated from ground and then switched on the power to them.

Tony

Tony Raven said:

Possible but difficult. The only situation I can think of off the top
of my head is if you held the live and neutral wires while relatively
insulated from ground and then switched on the power to them.

Stranger things have happened.

Most site electrical gear is 110V centre-tapped, so the actual voltage
to earth is generally 55V, being a low enough value that it's
considered basically safe.

One night shift, in a dozy frame of mind, when the temporary traffic
lights on my site stopped working I thought one of teh fuses had
blown. I didn't know which of teh fuses had blown, so I unscrewed the
two fuse caps, one with my left hand and one with my right hand. My
hands were wet, and I was wearing wellingtons...

Now I adopt the policy of keeping one hand in my pocket as much as
possible when doing anything with electricity.

regards, Ian SMith
--
|\ /| no .sig
|o o|
|/ \|

On Sat, 16 Oct 2004 12:30:14 +0100 someone who may be Tony Raven
<[email hidden]> wrote this:-

Quoted message said:

Possible but difficult. The only situation I can think of off the top
of my head is if you held the live and neutral wires while relatively
insulated from ground and then switched on the power to them.

This is a situation which can arise more often than you may think.
Cutting a two core cable and then examining the ends of the cable
without turning the electricity off is such a situation. Note that
shoes and floor coverings tend to have a very high resistance.

--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me by using the RIP Act 2000.

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David Hansen said:

On Sat, 16 Oct 2004 12:30:14 +0100 someone who may be Tony Raven
<[email hidden]> wrote this:-

Quoted message said:

Possible but difficult. The only situation I can think of off the top
of my head is if you held the live and neutral wires while relatively
insulated from ground and then switched on the power to them.

This is a situation which can arise more often than you may think.
Cutting a two core cable and then examining the ends of the cable
without turning the electricity off is such a situation. Note that
shoes and floor coverings tend to have a very high resistance.

Simply picking them up is unlikely to be sufficient because it will be
difficult to make contact with the two wires simultaneously. As soon as
you contact one wire and not the other there will be a differential
current flow that will trip the RCD. The only way other than extreme
misfortune to cause the current to flow simulateously is to have dead
wires and then switch the power onto them while holding them both

Tony

On Sat, 16 Oct 2004 11:30:54 +0100 someone who may be Jon Senior
<jon_AT_restlesslemon_DOTco_DOT_uk> wrote this:-

Quoted message said:

the
world in general (IEEE etc) seems to classify fuses as equipment
protection and RCDs as user protection.

Do they?

If they do then I would compare the standard of electrical
installations in the USA with those in the UK. I think that in
general the IEE has got it more right than the IEEE.

Quoted message said:

in most incidents involving
electrocution the victim forms a path to earth. In these incidents an
RCD will act at a much lower current than a fuse, limiting the damage.

You appear to only be considering direct contact. I am considering
both direct contact and indirect contact. Both will leave someone
dead.

Quoted message said:

Quoted message said:

One of the reasons standard domestic socket outlet circuits are
designed to disconnect in less than 0.4s if there is a fault is to
reduce the chances of electrocution. The device which does this is
the fuse you appear to dislike so much, or a miniature circuit
breaker and it usually operates far faster than 0.4s. A High
Breaking Capacity fuse will operate in rather less than a quarter of
a cycle, dramatically limiting the energy which is let through.

You are talking 400ms and 3A,

Incorrect, on two counts.

The first count where that comment is incorrect is the time of
operation. A cycle takes 20ms. In the case of direct contact the RCD
is likely to operate first, in one and a half cycles if it operates
in 30ms (40ms is more typical). In doing so there will be no current
limiting. In the case of indirect contact a HBC fuse will operate
first in most cases, in less than a quarter of a cycle or less than
5ms, limiting the current. Don't be fooled by the fact that the
IEE's current/time charts don't go that low. The RCD will operate
first in the case of indirect contact if the fault is of high
resistance.

The second count where that comment is incorrect is the fault
current. That depends on what the fault is. It might be less than
half an amp, it might be several thousand (even on a final circuit).
Few appreciate the sorts of current than will flow in a fault.

I have demonstrated to myself that a 45A HBC fuse will operate more
rapidly than a 30mA RCD. This was not deliberate by the way, don't
try this at home. I have also experienced faults where an RCD
operated before the fuse (or MCB) did.

As I said this is more complicated than it appears.

Note also that I recommended people use an RCD where socket circuits
are connected in a particularly hazardous situation.

--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me by using the RIP Act 2000.

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David Hansen [email hidden] opined the following...

Quoted message said:

Quoted message said:

the
world in general (IEEE etc) seems to classify fuses as equipment
protection and RCDs as user protection.

Do they?

Yes. Since an RCD is designed to shorten fault conditions where current
leaks to earth which would rarely damage equipment. In fact if you
remove users from the equation, I could not envisage any use for RCDs.

Quoted message said:

If they do then I would compare the standard of electrical
installations in the USA with those in the UK. I think that in
general the IEE has got it more right than the IEEE.

Because they agree with you presumably?

Quoted message said:

You appear to only be considering direct contact. I am considering
both direct contact and indirect contact. Both will leave someone
dead.

Not entirely sure what you mean by this. What do you mean by direct and
indirect contact?

Quoted message said:

Quoted message said:

You are talking 400ms and 3A,

Incorrect, on two counts.

You quoted 400ms, the minimum BS HBC fuse is 3A.

Quoted message said:

The first count where that comment is incorrect is the time of
operation. A cycle takes 20ms. In the case of direct contact the RCD
is likely to operate first, in one and a half cycles if it operates
in 30ms (40ms is more typical).

In observation (Part of my job includes industrial testing of RCDs) most
30ms, 30mA rated RCDs will trip in around 10ms at a current leakage of
between 15mA and 30mA. There is sometimes a minor variance (~5ms)
between 0 degree and 180 degree triggering.

Quoted message said:

In doing so there will be no current
limiting. In the case of indirect contact a HBC fuse will operate
first in most cases, in less than a quarter of a cycle or less than
5ms, limiting the current. Don't be fooled by the fact that the
IEE's current/time charts don't go that low. The RCD will operate
first in the case of indirect contact if the fault is of high
resistance.

But the main issue is that death from electrocution is a combination of
exposure current and exposure time. A very high current requires less
time. Below 300mA the times become significant (Much above that and the
safe exposure time is so small as to be effectively irrelevant).

If an appliance is fitted with a 13A fuse then it is possible to take
the full 13A across the heart before the fuse blows. If something acts
to limit the current (High resistance to earth?) then it is possible
that the fuse will not blow at all.

Quoted message said:

The second count where that comment is incorrect is the fault
current. That depends on what the fault is. It might be less than
half an amp, it might be several thousand (even on a final circuit).
Few appreciate the sorts of current than will flow in a fault.

The problem is that a current flow above the levels at which RCDs are
designed to operate, but below that of normal fuses can easily kill.

Overcurrent protection is generally considered to be to protect wiring
from overheating and thus reduce the incident of electrical fires. RCD
ptotection is there to protect the end user. This is why modern
electrical installations offer RCD protection of user-accessible sockets
(This is mandatory) but not generally of lighting rings where user
contact is minimal.

Quoted message said:

I have demonstrated to myself that a 45A HBC fuse will operate more
rapidly than a 30mA RCD. This was not deliberate by the way, don't
try this at home.

I have also managed to "test" a few protection systems and have learnt
from my mistakes. None of my tests were intentional. No amount of
confidence in an RCD / MCB / fuse would encourage me to "touch the shiny
bits"! ;-)

Quoted message said:

I have also experienced faults where an RCD
operated before the fuse (or MCB) did.

As I said this is more complicated than it appears.

Note also that I recommended people use an RCD where socket circuits
are connected in a particularly hazardous situation.

Sorry if I came across as attacking you. I would personally rather
people put both MCBs / fuses and RCDs on everything. The more RCDs are
used, the more the prices will drop and the more realistic it will be to
put them in everywhere. If I ever get my own house (And the budget to do
it) the wiring will be _very_ safe!

Jon

On Sat, 16 Oct 2004 16:40:10 +0100 someone who may be Jon Senior
<jon_AT_restlesslemon_DOTco_DOT_uk> wrote this:-

Quoted message said:

Not entirely sure what you mean by this. What do you mean by direct and
indirect contact?

They are standard terms.

Direct contact is self-explanatory.

Indirect contact is contact with exposed conductive parts which have
been made live by a fault. One of the things to consider in this
situation is that people will not expect such parts to be live.

Quoted message said:

You quoted 400ms,

Not quite.

I'm not quite sure how I could re-phrase "One of the reasons
standard domestic socket outlet circuits are designed to disconnect
in less than 0.4s".

I explained three different scenarios, in which different devices
will operate first depending on the situation.

Quoted message said:

If an appliance is fitted with a 13A fuse then it is possible to take
the full 13A across the heart before the fuse blows.

We come back to direct and indirect contact.

Quoted message said:

If something acts
to limit the current (High resistance to earth?) then it is possible
that the fuse will not blow at all.

High fault resistance is a factor I commented on before.

Quoted message said:

The problem is that a current flow above the levels at which RCDs are
designed to operate, but below that of normal fuses can easily kill.

We come back to direct and indirect contact.

Quoted message said:

Overcurrent protection is generally considered to be to protect wiring
from overheating and thus reduce the incident of electrical fires.

That is just one of the reasons for having such protection. We come
back to direct and indirect contact.

Quoted message said:

This is why modern
electrical installations offer RCD protection of user-accessible sockets
(This is mandatory)

Not quite. Various things to do with RCDs and some final circuits
are mandatory in Scotland (I have lost track of the position down
south regarding whether it is mandatory or just good practice). This
varies with time, with the regulations getting more restrictive as
time passes. The reasons for this are sensible.

Quoted message said:

but not generally of lighting rings where user contact is minimal.

I look forward to seeing a lighting ring final circuit. One would be
most interesting, though I can see no reason for one.

In the meantime I will stick with final circuits feeding fixed
equipment (which includes lighting circuits). Quite rightly these
are allowed longer disconnection times than final circuits feeding
socket outlets (for the reason you gave).

Quoted message said:

No amount of
confidence in an RCD / MCB / fuse would encourage me to "touch the shiny
bits"! ;-)

It is no big deal. They tend to feel cold, as one would expect of a
metal item, though if carrying a large current (for the size of
conductor) then they may be very hot. Those who work on live 400,000
volt cables do so inside heat resisting suits, because the
temperature of the conductor would probably burn their unprotected
hands. I have never done this, but it would be great fun as a
wonderful arc can be drawn between the conductor and one's hand.
Obviously this is not a power arc. The same sort of arc can be seen
between train pantographs and the overhead wiring when the
pantograph is raised or lowered

**** Note for those who are stupid **** touching live parts is
something that skilled persons can do in some circumstances, with a
relatively low risk of killing themselves. However, a skilled person
knows what they are doing and so is able to minimise the danger to
themselves (and any others). You don't know what you are doing and
so are likely to kill yourself. You have been warned. Despite being
competent to work live I always turn off the electricity before
doing any wiring work.

Quoted message said:

If I ever get my own house (And the budget to do
it) the wiring will be _very_ safe!

Let me be blunt. Get some who understands electrical installations
to do the wiring.

--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me by using the RIP Act 2000.

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On 16/10/04 11:46 pm, in article [email hidden],

David Hansen said:

Quoted message said:

If I ever get my own house (And the budget to do
it) the wiring will be _very_ safe!

Let me be blunt. Get some who understands electrical installations
to do the wiring.

I mentioned to my brother that I was doing a simple bit of wiring and he
threw the book at me.. The IEE+ one. Scary stuff. It does make you realise
just how little you do actually know as an intelligent layman.

I'll stick to simple things now, like plugs..

...d

On Sat, 16 Oct 2004 23:55:04 +0100 someone who may be David Martin
<[email hidden]> wrote this:-

Quoted message said:

I mentioned to my brother that I was doing a simple bit of wiring and he
threw the book at me.. The IEE+ one. Scary stuff. It does make you realise
just how little you do actually know as an intelligent layman.

If it was BS7671 then one of the problems is that it has been
"harmonised". The result of such "harmonisation" is generally that
many words are used to say relatively little. That is the case with
BS7671. Then you get to things like the year 2000 changes to
bathroom wiring standards (mostly rather pointless) and the current
changes to cable colours (sensible but difficult). Like many
reference documents it only makes sense when you know all the
contents. Computer manuals tend to be similarly badly written.

However, BS7671 is converted into something more readable in a
variety of guides that can be purchased. These are a better bet for
those who want to gain an insight and are used a lot in the
industry.

--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me by using the RIP Act 2000.

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David Martin [email hidden] opined the following...

Quoted message said:

I mentioned to my brother that I was doing a simple bit of wiring and he
threw the book at me.. The IEE+ one. Scary stuff. It does make you realise
just how little you do actually know as an intelligent layman.

Not that scary, just masked in vague language. The pertinent points boil
down to not exposing anyone to unnecessary risk.

Quoted message said:

I'll stick to simple things now, like plugs..

Which, given some of the plugs I've seen[1], would appear to be a more
complex task than you'd credit.

Jon

[1] Excessive stripping of insulation, incorrect or non-existent cable
clamping, live / neutral swaps, earth disconnected and once, a wire
clamped into a fuse holder with a blown fuse.

David Hansen [email hidden] opined the following...

Quoted message said:

They are standard terms.

Direct contact is self-explanatory.

Indirect contact is contact with exposed conductive parts which have
been made live by a fault. One of the things to consider in this
situation is that people will not expect such parts to be live.

As in metallic / conducting surfaces in a Class I device? Since the
surface is live, you are directly contacting a live surface. Seems a
strangely redundant term.

Quoted message said:

We come back to direct and indirect contact.

I fail to understand the difference between these two situations. Both
boil down to touching a surface that is live. Whether that surface
should be or not makes no difference to the nature of the protection
offered by fuses, MCBs or RCDs.

Quoted message said:

High fault resistance is a factor I commented on before.

Indeed, and a high resistance could lead to a situation where a fuse did
not blow because the current flow was less than its rated value. It
would thus offer no protection.

Quoted message said:

We come back to direct and indirect contact.

Which still appears to be of no relevance.

Quoted message said:

That is just one of the reasons for having such protection. We come
back to direct and indirect contact.

See above. Or explain.

Quoted message said:

Not quite. Various things to do with RCDs and some final circuits
are mandatory in Scotland (I have lost track of the position down
south regarding whether it is mandatory or just good practice). This
varies with time, with the regulations getting more restrictive as
time passes. The reasons for this are sensible.

In England all new electrical installations which involve sockets that
are accessible by the public MUST be protected by an RCD / MCB
combination.

Quoted message said:

It is no big deal. They tend to feel cold, as one would expect of a
metal item, though if carrying a large current (for the size of
conductor) then they may be very hot.

It was the advice given before starting a hands-on maintenance course
for electric chain hoists. "Do not touch the shiny bits! It saves us a
lot of paperwork." ;-)

Quoted message said:

Those who work on live 400,000
volt cables do so inside heat resisting suits, because the
temperature of the conductor would probably burn their unprotected
hands. I have never done this, but it would be great fun as a
wonderful arc can be drawn between the conductor and one's hand.
Obviously this is not a power arc. The same sort of arc can be seen
between train pantographs and the overhead wiring when the
pantograph is raised or lowered

One of my colleagues has taken to playing with HV devices. With a few
transformer coils and an electronic transformer for low vtage lighting
he can generate a really pretty arc across about 4cm of air.

Quoted message said:

Let me be blunt. Get some who understands electrical installations
to do the wiring.

That wouldn't include many of the electricians that I've had the
misfortune to encounter so far. During the installation of his new
shower, the sparkie managed to somehow disconnect the hall light. When
we took out his old kitchen, the ring was just laid under the cupboards
with at least one "connection" where two ends of wire had been twisted
together and taped up with PVC. My father understands electrical
installations, a number of my colleagues do so as well. Where I to
undergo such a project I would seek advice from a range of sources but
ensure that I was able to either carry out the work or supervise it
closely. The only real reason for hiring a "professional" is to have
someone to blame!

Jon

David Martin said:

I mentioned to my brother that I was doing a simple bit of wiring and he
threw the book at me.. The IEE+ one. Scary stuff. It does make you realise
just how little you do actually know as an intelligent layman.

I'll stick to simple things now, like plugs..

From the end of the year it will be illegal to DIY with electrics in
the home. If you want to do it yourself you have to have started the
work before Jan 1 which you will be allowed to complete. Otherwise its
call in a qualified electrician to do it.

http://www.niceic.org.uk/partp/newsitem_sept0704.htm

Tony

On Sun, 17 Oct 2004 01:08:42 +0100 someone who may be Jon Senior
<jon_AT_restlesslemon_DOTco_DOT_uk> wrote this:-

Quoted message said:

Quoted message said:

Indirect contact is contact with exposed conductive parts which have
been made live by a fault. One of the things to consider in this
situation is that people will not expect such parts to be live.

As in metallic / conducting surfaces in a Class I device? Since the
surface is live, you are directly contacting a live surface. Seems a
strangely redundant term.

You may think so. However, the difference between direct and
indirect contact is clear enough. If the insulation is missing from
a kettle switch then that is direct contact. If the casing of the
kettle is live then that is indirect contact.

In the case of indirect contact the electrical system can detect the
fault as soon as it happens and disconnect the kettle before someone
picks it up. If someone happens to be holding the kettle when the
fault occurs then if the fault is of low resistance the fuse will
operate first, limiting the energy let through. If it is of high
resistance then the RCD may operate first, though these do not limit
the energy let through.

Quoted message said:

Quoted message said:

Let me be blunt. Get some who understands electrical installations
to do the wiring.

That wouldn't include many of the electricians that I've had the
misfortune to encounter so far.

Did I mention electricians?

--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me by using the RIP Act 2000.

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On 17/10/04 12:51 am, in article [email hidden],

Jon Senior' jon_AT_restlesslemon_DOTco_DOT_uk said:

David Martin [email hidden] opined the following...

Quoted message said:

I mentioned to my brother that I was doing a simple bit of wiring and he
threw the book at me.. The IEE+ one. Scary stuff. It does make you realise
just how little you do actually know as an intelligent layman.

Not that scary, just masked in vague language. The pertinent points boil
down to not exposing anyone to unnecessary risk.

It was mostly the bits about load for given cable widths, how many wires can
go in what kind of conduit etc for heat loss to be effective. Stuff that had
never really crossed my mind. (Not that running a cable to the garage
required such considerations.. note to self: install RCD in the garage.)

Quoted message said:

Quoted message said:

I'll stick to simple things now, like plugs..

Which, given some of the plugs I've seen[1], would appear to be a more
complex task than you'd credit.

Any fool can screw up the easiest of tasks. Anyway, as it was on my physics
O Level syllabus, I am qualified to wire a plug!

...d