On Wed, 03 Apr 2013 06:01:43 +0100, John Rumm wrote:

On 02/04/2013 22:47, Major Scott wrote:
On Tue, 02 Apr 2013 21:48:11 +0100, John Rumm

Note also that is the conductor temperature. There will be a temperature
gradient across the insulation, so the touch temperature of the
insulation on the outside will be lower.

I've got copper heating pipes in my airing cupboard that get that hot,
and I don't much like bottles of stuff being against them.

Are they covered in PVC insulation as well?

Do your "bottles of stuff" catch fire?

Is you house built from "bottles of stuff"?

The bottles would melt.

--
You can listen to thunder after lightning to tell how close you came to getting hit. If you don't hear it never mind.

On Wed, 03 Apr 2013 06:02:51 +0100, John Rumm wrote:

On 02/04/2013 22:12, Alexander Lamaison wrote:
"Major Scott" writes:

On Tue, 02 Apr 2013 20:40:58 +0100, ARW wrote:

Major Scott wrote:
On Tue, 02 Apr 2013 17:53:00 +0100, ARW
wrote:


It's not just the cable that gets hot though. I don't want my
flammable wall that warm.

So you live in a caravan?

Put a match to your wallpaper. Or plasterboard.

So now this apocalyptic socket is running at 600C?

Perhaps his anal vibrator goes up to 11?

Not if the socket can't give it 13A.

--
There are more men than women in mental hospitals - which just goes to show who's driving who crazy.

On Wed, 03 Apr 2013 12:19:04 +0100, John Rumm wrote:

On 03/04/2013 12:05, Major Scott wrote:
On Wed, 03 Apr 2013 06:20:02 +0100, John Rumm
wrote:

On 02/04/2013 22:30, Major Scott wrote:

In a portable appliance you don't fit a fuse higher than the flex is
rated.

Erm, in fact its commonly done... (and safely)

Not safe at all. 5A flex, 13A fuse, for some reason the device goes
wrong and draws 13A. Flex causes fire.

Bzzzzrt Is the wrong answer...

Now think a bit harder - all the information has been posted for you.

Imagine a table lamp, "3A flex", 13A fuse?

Or look at the IEC power lead in the back of your computer.... plenty of
those with 13A fuses - the cable is not 1.5mm^2 though.

Or imagine your appliance used in Germany, 16A MCB at the circuit
origin, no fuse in the plug at all, same "less than 13A capable" flex.

Yet it all still works and fails safe, how can that be?

I do not ever put a 13A fuse in a table lamp with a 3A cord, that's just stupid. Why do you think there are 3A fuses in shops?

--
Love conquers all, except in tennis.

Dave Liquorice wrote:
On Tue, 02 Apr 2013 23:28:35 +0100, Alexander Lamaison wrote:

Actually paper ignites at 233C.

450C actually [1], but who's counting? And I was talking about the
match.

451 F as in Fahrenheit 451 by Ray Bradbury

One of my all time favourite films.A blonde bird once asked me what I wanted
for my Birthday and I asked for Fahrenheit 451 on DVD.

I was most disappointed when she got confused and bought Fahrenheit 9/11
instead. Mind you she managed to get To Sir, with Love (an ever better film)
on DVD for Xmas without ****ing it up.


[1] http://en.wikipedia.org/wiki/Autoignition_temperature

Which quotes both figures, 450 C and 218 - 246 C (424 - 475 F).

The talk page makes for interesting reading.

Thanks for that. Most interesting.

--
Adam

On 03/04/2013 18:28, ARW wrote:
One of my all time favourite films.A blonde bird once asked me what I wanted
for my Birthday and I asked for Fahrenheit 451 on DVD.

Of ALL the bits of literature that shouldn't be a movie I would have
thought that that ought to be first.

Andy

On 03/04/2013 15:41, Major Scott wrote:
On Tue, 02 Apr 2013 23:43:40 +0100, Alexander Lamaison
wrote:

"Major Scott" writes:

On Tue, 02 Apr 2013 22:27:33 +0100, Tim Watts
wrote:

On Tuesday 02 April 2013 19:41 Major Scott wrote in uk.d-i-y:

People with fuses aren't so worried about quick trips.

You ****ign well should be - you are required to meet the 0.4second
disconnection time, with an overcurrent device. The type of device is
irrelevant.

Required am I? I'll make the decisions around here, not a committee.

You rail at the very thought of a 20A double socket but are blaze about
a 0.4s disconnection time. Time to get out the hammer and knock those
priorities straight.

Fire concerns me more than electric shock.

Which (if you had any functional understanding of the issues) would make
you far more concerned about having suitably short disconnection times
under fault conditions than prattling on about socket current ratings.


--
Cheers,

John.

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

On 03/04/2013 15:47, Major Scott wrote:
On Wed, 03 Apr 2013 12:19:04 +0100, John Rumm
wrote:

On 03/04/2013 12:05, Major Scott wrote:
On Wed, 03 Apr 2013 06:20:02 +0100, John Rumm
wrote:

On 02/04/2013 22:30, Major Scott wrote:

In a portable appliance you don't fit a fuse higher than the flex is
rated.

Erm, in fact its commonly done... (and safely)

Not safe at all. 5A flex, 13A fuse, for some reason the device goes
wrong and draws 13A. Flex causes fire.

Bzzzzrt Is the wrong answer...

Now think a bit harder - all the information has been posted for you.

Imagine a table lamp, "3A flex", 13A fuse?

Or look at the IEC power lead in the back of your computer.... plenty of
those with 13A fuses - the cable is not 1.5mm^2 though.

Or imagine your appliance used in Germany, 16A MCB at the circuit
origin, no fuse in the plug at all, same "less than 13A capable" flex.

Yet it all still works and fails safe, how can that be?

I do not ever put a 13A fuse in a table lamp with a 3A cord, that's just
stupid. Why do you think there are 3A fuses in shops?

Explain how you think it works in countries other than the UK...


--
Cheers,

John.

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

On Wed, 03 Apr 2013 20:21:55 +0100, John Rumm wrote:

On 03/04/2013 15:41, Major Scott wrote:
On Tue, 02 Apr 2013 23:43:40 +0100, Alexander Lamaison
wrote:

"Major Scott" writes:

On Tue, 02 Apr 2013 22:27:33 +0100, Tim Watts
wrote:

On Tuesday 02 April 2013 19:41 Major Scott wrote in uk.d-i-y:



You ****ign well should be - you are required to meet the 0.4second
disconnection time, with an overcurrent device. The type of device is
irrelevant.

Required am I? I'll make the decisions around here, not a committee.

You rail at the very thought of a 20A double socket but are blaze about
a 0.4s disconnection time. Time to get out the hammer and knock those
priorities straight.

Fire concerns me more than electric shock.

Which (if you had any functional understanding of the issues) would make
you far more concerned about having suitably short disconnection times
under fault conditions than prattling on about socket current ratings.

I can't see a fire starting in 1 second.

--
When working with electronics, my best advice is to do whatever it takes to prevent the smoke from leaking out of the components. Electronic parts require the smoke to stay inside to function correctly!

On Wed, 03 Apr 2013 20:21:55 +0100, John Rumm wrote:

On 03/04/2013 15:41, Major Scott wrote:
On Tue, 02 Apr 2013 23:43:40 +0100, Alexander Lamaison
wrote:

"Major Scott" writes:

On Tue, 02 Apr 2013 22:27:33 +0100, Tim Watts
wrote:

On Tuesday 02 April 2013 19:41 Major Scott wrote in uk.d-i-y:



You ****ign well should be - you are required to meet the 0.4second
disconnection time, with an overcurrent device. The type of device is
irrelevant.

Required am I? I'll make the decisions around here, not a committee.

You rail at the very thought of a 20A double socket but are blaze about
a 0.4s disconnection time. Time to get out the hammer and knock those
priorities straight.

Fire concerns me more than electric shock.

Which (if you had any functional understanding of the issues) would make
you far more concerned about having suitably short disconnection times
under fault conditions than prattling on about socket current ratings.

And elsewhere in the thread people are saying it's ok to protect a device with a 3A flex with a 13A fuse!!!!

--
Why don't Siamese cats come in pairs?

On Wed, 03 Apr 2013 20:27:15 +0100, John Rumm wrote:

On 03/04/2013 15:47, Major Scott wrote:
On Wed, 03 Apr 2013 12:19:04 +0100, John Rumm
wrote:

On 03/04/2013 12:05, Major Scott wrote:
On Wed, 03 Apr 2013 06:20:02 +0100, John Rumm
wrote:

On 02/04/2013 22:30, Major Scott wrote:



Erm, in fact its commonly done... (and safely)

Not safe at all. 5A flex, 13A fuse, for some reason the device goes
wrong and draws 13A. Flex causes fire.

Bzzzzrt Is the wrong answer...

Now think a bit harder - all the information has been posted for you.

Imagine a table lamp, "3A flex", 13A fuse?

Or look at the IEC power lead in the back of your computer.... plenty of
those with 13A fuses - the cable is not 1.5mm^2 though.

Or imagine your appliance used in Germany, 16A MCB at the circuit
origin, no fuse in the plug at all, same "less than 13A capable" flex.

Yet it all still works and fails safe, how can that be?

I do not ever put a 13A fuse in a table lamp with a 3A cord, that's just
stupid. Why do you think there are 3A fuses in shops?

Explain how you think it works in countries other than the UK...

Their safety isn't as good as ours.

--
The sailor does not pray for wind, he learns to sail -- Gustaf Lindborg

Andy Champ wrote:
On 03/04/2013 18:28, ARW wrote:
One of my all time favourite films.A blonde bird once asked me what
I wanted for my Birthday and I asked for Fahrenheit 451 on DVD.

Of ALL the bits of literature that shouldn't be a movie I would have
thought that that ought to be first.

Why?


--
Adam

On Wednesday 03 April 2013 15:32 Major Scott wrote in uk.d-i-y:


Incorrect. The only problem people have with me is I'm not a brainwashed
health and safety moronic sheep like the rest of you.

Correct. You're just moronic.

--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

Reading this on the web? See:
http://wiki.diyfaq.org.uk/index.php?title=Usenet

On Wednesday 03 April 2013 15:42 Major Scott wrote in uk.d-i-y:

Fuses are great, they don't have a hair trigger.


Neither do circuit breakers.

--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

Reading this on the web? See:
http://wiki.diyfaq.org.uk/index.php?title=Usenet

On Wed, 03 Apr 2013 21:03:50 +0100, Tim Watts wrote:

On Wednesday 03 April 2013 15:32 Major Scott wrote in uk.d-i-y:


Incorrect. The only problem people have with me is I'm not a brainwashed
health and safety moronic sheep like the rest of you.

Correct. You're just moronic.

You've just proved what I just said. You have no reason for following all these rules, you just do it like a robot. I get the feeling I'm surrounded by clones, possibly controlled remotely from 10 Downing Street.

--
Das Computer Maschine Ist Nich Fur Gefingerenpoken Und Mittengrabben!
Ist Easy Schnappen Der Springenwerken Mit Spitzensparken Und Poppenkorken!
Das Rubbernecken Sightseeren Mus Keep Der Handz In Der Pockets, Relax Und Vatch Die Blinkenlights!!

On 03/04/2013 15:43, Major Scott wrote:
On Tue, 02 Apr 2013 22:22:36 +0100, John Rumm
wrote:

On 02/04/2013 19:43, Major Scott wrote:
On Tue, 02 Apr 2013 19:06:01 +0100, Tim Watts
wrote:

On Tuesday 02 April 2013 18:48 Major Scott wrote in uk.d-i-y:

Read up about diversity factor.
http://en.wikipedia.org/wiki/Diversi...versified_Load

I'm not into gambling.


The you should probably ask your electricy company for a 150A supply
depending of whether you have an electric shower and cooker.

And a road with 100 houses should be supplied with 5000A 3 phase
cables.

etc etc.

No, it's fine as long as there is adequate protection. The electricity
board assumes I will never use more than 100 amps. But if I did, the
fuse next to the meter would blow.

Unlikely on both counts...

They are assuming you will use an average of around 8A

Your fuse won't blow at 100A (unless its a 40A one)

You know what I mean, obviously I can have surges.

Would you call 150A for an hour a "surge"?

(because that won't blow your 100A fuse either...)

But assuming nobody will ever draw 26 amps from a double socket, and
having no protection if it did happen, is daft.

Just as well no one makes that assumption then.

The sockets are only tested at 20A.

for a minimum of 4 hours...

Your 2 x 13A loads will average less than that.


--
Cheers,

John.

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

On 03/04/2013 20:29, Major Scott wrote:
On Wed, 03 Apr 2013 20:27:15 +0100, John Rumm
wrote:

On 03/04/2013 15:47, Major Scott wrote:
On Wed, 03 Apr 2013 12:19:04 +0100, John Rumm
wrote:

On 03/04/2013 12:05, Major Scott wrote:
On Wed, 03 Apr 2013 06:20:02 +0100, John Rumm
wrote:

On 02/04/2013 22:30, Major Scott wrote:



Erm, in fact its commonly done... (and safely)

Not safe at all. 5A flex, 13A fuse, for some reason the device goes
wrong and draws 13A. Flex causes fire.

Bzzzzrt Is the wrong answer...

Now think a bit harder - all the information has been posted for you.

Imagine a table lamp, "3A flex", 13A fuse?

Or look at the IEC power lead in the back of your computer....
plenty of
those with 13A fuses - the cable is not 1.5mm^2 though.

Or imagine your appliance used in Germany, 16A MCB at the circuit
origin, no fuse in the plug at all, same "less than 13A capable" flex.

Yet it all still works and fails safe, how can that be?

I do not ever put a 13A fuse in a table lamp with a 3A cord, that's just
stupid. Why do you think there are 3A fuses in shops?

Explain how you think it works in countries other than the UK...

Their safety isn't as good as ours.

Try again, that does not answer the question....



--
Cheers,

John.

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

On Wed, 03 Apr 2013 21:52:01 +0100, John Rumm wrote:

On 03/04/2013 15:43, Major Scott wrote:
On Tue, 02 Apr 2013 22:22:36 +0100, John Rumm
wrote:

On 02/04/2013 19:43, Major Scott wrote:
On Tue, 02 Apr 2013 19:06:01 +0100, Tim Watts
wrote:

On Tuesday 02 April 2013 18:48 Major Scott wrote in uk.d-i-y:



The you should probably ask your electricy company for a 150A supply
depending of whether you have an electric shower and cooker.

And a road with 100 houses should be supplied with 5000A 3 phase
cables.

etc etc.

No, it's fine as long as there is adequate protection. The electricity
board assumes I will never use more than 100 amps. But if I did, the
fuse next to the meter would blow.

Unlikely on both counts...

They are assuming you will use an average of around 8A

Your fuse won't blow at 100A (unless its a 40A one)

You know what I mean, obviously I can have surges.

Would you call 150A for an hour a "surge"?

(because that won't blow your 100A fuse either...)

It should. Why call it a 100A fuse if you can use way more than that indefinitely?

But assuming nobody will ever draw 26 amps from a double socket, and
having no protection if it did happen, is daft.

Just as well no one makes that assumption then.

The sockets are only tested at 20A.

for a minimum of 4 hours...

Your 2 x 13A loads will average less than that.

I know a woman who melted a 4 way extension strip with two tumble driers and 2 washing machines. Some 13A fuse that was.....

--
It's an age-old truism. Men will quickly fall asleep after having sex.
And I know why, too.
It's because they've been up half the night begging for it.

On Wed, 03 Apr 2013 21:55:10 +0100, John Rumm wrote:

On 03/04/2013 20:29, Major Scott wrote:
On Wed, 03 Apr 2013 20:27:15 +0100, John Rumm
wrote:

On 03/04/2013 15:47, Major Scott wrote:
On Wed, 03 Apr 2013 12:19:04 +0100, John Rumm
wrote:

On 03/04/2013 12:05, Major Scott wrote:




Bzzzzrt Is the wrong answer...

Now think a bit harder - all the information has been posted for you.

Imagine a table lamp, "3A flex", 13A fuse?

Or look at the IEC power lead in the back of your computer....
plenty of
those with 13A fuses - the cable is not 1.5mm^2 though.

Or imagine your appliance used in Germany, 16A MCB at the circuit
origin, no fuse in the plug at all, same "less than 13A capable" flex.

Yet it all still works and fails safe, how can that be?

I do not ever put a 13A fuse in a table lamp with a 3A cord, that's just
stupid. Why do you think there are 3A fuses in shops?

Explain how you think it works in countries other than the UK...

Their safety isn't as good as ours.

Try again, that does not answer the question....

You asked how it worked. Of course it will work, it just won't protect well against fire.

--
A man is a person who will pay two dollars for a one-dollar item he wants.
A woman will pay one dollar for a two-dollar item that she doesn't want.

On Wed, 03 Apr 2013 21:11:21 +0100, Tim Watts wrote:

On Wednesday 03 April 2013 15:42 Major Scott wrote in uk.d-i-y:

Fuses are great, they don't have a hair trigger.

Neither do circuit breakers.

They blow faster.

--
There's a word you are misunderstanding or misinterpreting, whether explicitly or by necessary and inescapable implication.

On Wed, 03 Apr 2013 22:10:55 +0100, Major Scott wrote:

On Wed, 03 Apr 2013 21:11:21 +0100, Tim Watts wrote:

On Wednesday 03 April 2013 15:42 Major Scott wrote in uk.d-i-y:

Fuses are great, they don't have a hair trigger.

Neither do circuit breakers.

They blow faster.

And the earth leakage ones are a nuisance.

--
There's a word you are misunderstanding or misinterpreting, whether explicitly or by necessary and inescapable implication.

On 2013-04-03, John Rumm wrote:

Bzzzzrt Is the wrong answer...

Now think a bit harder - all the information has been posted for you.

Imagine a table lamp, "3A flex", 13A fuse?

Or look at the IEC power lead in the back of your computer.... plenty of
those with 13A fuses - the cable is not 1.5mm^2 though.

Or imagine your appliance used in Germany, 16A MCB at the circuit
origin, no fuse in the plug at all, same "less than 13A capable" flex.

Hang on, it's dogma here that British wiring is vastly superior to
everything else, & that once you plug things in in foreign countries,
all bets are off & you're dicing with death.


Yet it all still works and fails safe, how can that be?

OK, seriously, is it impossible or just very unlikely for a portable
appliance to develop a fault (not a dead short) that will present a
fire hazard without blowing the 13Â*A fuse in the plug?

Why do we need 1, 3, 5, & 10 A plug fuses?

On 2013-04-03, ARW wrote:

Andy Champ wrote:
On 03/04/2013 18:28, ARW wrote:
One of my all time favourite films.A blonde bird once asked me what
I wanted for my Birthday and I asked for Fahrenheit 451 on DVD.

Of ALL the bits of literature that shouldn't be a movie I would have
thought that that ought to be first.

Why?

IIRC, Bradbury said the book was primarily about the harmful effects
of TV, rather than about censorship.

On 03/04/2013 20:29, Major Scott wrote:
On Wed, 03 Apr 2013 20:21:55 +0100, John Rumm
wrote:

On 03/04/2013 15:41, Major Scott wrote:
On Tue, 02 Apr 2013 23:43:40 +0100, Alexander Lamaison
wrote:

"Major Scott" writes:

On Tue, 02 Apr 2013 22:27:33 +0100, Tim Watts
wrote:

On Tuesday 02 April 2013 19:41 Major Scott wrote in uk.d-i-y:



You ****ign well should be - you are required to meet the 0.4second
disconnection time, with an overcurrent device. The type of device is
irrelevant.

Required am I? I'll make the decisions around here, not a committee.

You rail at the very thought of a 20A double socket but are blaze about
a 0.4s disconnection time. Time to get out the hammer and knock those
priorities straight.

Fire concerns me more than electric shock.

Which (if you had any functional understanding of the issues) would make
you far more concerned about having suitably short disconnection times
under fault conditions than prattling on about socket current ratings.

And elsewhere in the thread people are saying it's ok to protect a
device with a 3A flex with a 13A fuse!!!!

No, they are saying its ok to "protect" a 3A flex with a 13A fuse... a
subtle by very significant difference. The protection that is being
discussed (and the *only* one that matters with modern[1] appliances) is
fault protection.

If a device needs overload protection, then it must be built into the
device itself, since in most countries there will be no fuse in the plug
to offer it. If a device is put on the market in one EU country, then it
must be safe to sell it in all of them.

The flex needs fault protection. In the UK you can't rely on the
circuit's MCB / fuse to provide that, since it will typically be a 20 or
32A circuit (a 32A MCB needs at least 160A of fault current to ensure
disconnection via its "instant" magnetic response). Hence the need for
the plug fuse. A 13A plug fuse is quite capable of giving adequate fault
protection to a flex with a lower nominal continuous current rating. The
nominal current rating is based on maintaining conductor temperatures at
70 degrees or below, during long term sustained loads, and while able to
cool by natural means. This has little or no relevance to the same flex
under fault conditions where it is experiencing adiabatic heating due to
several hundred amps of fault current, and terminal conductor
temperatures of significantly more than 70 deg C are acceptable.

Could I suggest if you want to carry on discussing this further that you
try and make an effort to comprehend the different types of protection
that fuses and MCBs provide?

This has nothing to do with "rules" or elf'n'safety, and everything to
do with really quite basic physics.

[1] Some very old appliances (i.e. pre 70s) designed just for the UK
market, may be reliant on a plug fuse for overload protection as well.
With these it is important that you use the manufacturers recommended fuse.


--
Cheers,

John.

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

On 03/04/2013 20:28, Major Scott wrote:
On Wed, 03 Apr 2013 20:21:55 +0100, John Rumm
wrote:

On 03/04/2013 15:41, Major Scott wrote:
On Tue, 02 Apr 2013 23:43:40 +0100, Alexander Lamaison
wrote:

"Major Scott" writes:

On Tue, 02 Apr 2013 22:27:33 +0100, Tim Watts
wrote:

On Tuesday 02 April 2013 19:41 Major Scott wrote in uk.d-i-y:



You ****ign well should be - you are required to meet the 0.4second
disconnection time, with an overcurrent device. The type of device is
irrelevant.

Required am I? I'll make the decisions around here, not a committee.

You rail at the very thought of a 20A double socket but are blaze about
a 0.4s disconnection time. Time to get out the hammer and knock those
priorities straight.

Fire concerns me more than electric shock.

Which (if you had any functional understanding of the issues) would make
you far more concerned about having suitably short disconnection times
under fault conditions than prattling on about socket current ratings.

I can't see a fire starting in 1 second.

Which only further demonstrates your deep misunderstanding of the issues.

What do you suppose would happen if you take your combustible material
and spray it with a mixture of molten copper and burning PVC? Perhaps
also expose it to a fireball and an explosive arc flash just for good
measure...

You see, that *would* actually concern me as a proper fire risk.








--
Cheers,

John.

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

On Wed, 03 Apr 2013 22:27:46 +0100, John Rumm wrote:

On 03/04/2013 20:28, Major Scott wrote:
On Wed, 03 Apr 2013 20:21:55 +0100, John Rumm
wrote:

On 03/04/2013 15:41, Major Scott wrote:
On Tue, 02 Apr 2013 23:43:40 +0100, Alexander Lamaison
wrote:

"Major Scott" writes:





You rail at the very thought of a 20A double socket but are blaze about
a 0.4s disconnection time. Time to get out the hammer and knock those
priorities straight.

Fire concerns me more than electric shock.

Which (if you had any functional understanding of the issues) would make
you far more concerned about having suitably short disconnection times
under fault conditions than prattling on about socket current ratings.

I can't see a fire starting in 1 second.

Which only further demonstrates your deep misunderstanding of the issues.

What do you suppose would happen if you take your combustible material
and spray it with a mixture of molten copper and burning PVC? Perhaps
also expose it to a fireball and an explosive arc flash just for good
measure...

You see, that *would* actually concern me as a proper fire risk.

Maybe if my wall was soaked with petrol.

--
The graduate with a science degree asks, "Why does it work?"
The graduate with an engineering degree asks, "How does it work?"
The graduate with an accounting degree asks, "How much will it cost?"
The graduate with an arts degree asks, "Do you want fries with that?"

On 03/04/2013 22:27, Major Scott wrote:
On Wed, 03 Apr 2013 22:24:35 +0100, John Rumm
wrote:

On 03/04/2013 20:29, Major Scott wrote:
On Wed, 03 Apr 2013 20:21:55 +0100, John Rumm
wrote:

On 03/04/2013 15:41, Major Scott wrote:
On Tue, 02 Apr 2013 23:43:40 +0100, Alexander Lamaison
wrote:

"Major Scott" writes:





You rail at the very thought of a 20A double socket but are blaze
about
a 0.4s disconnection time. Time to get out the hammer and knock
those
priorities straight.

Fire concerns me more than electric shock.

Which (if you had any functional understanding of the issues) would
make
you far more concerned about having suitably short disconnection times
under fault conditions than prattling on about socket current ratings.

And elsewhere in the thread people are saying it's ok to protect a
device with a 3A flex with a 13A fuse!!!!

No, they are saying its ok to "protect" a 3A flex with a 13A fuse... a
subtle by very significant difference. The protection that is being
discussed (and the *only* one that matters with modern[1] appliances) is
fault protection.

If a device needs overload protection, then it must be built into the
device itself, since in most countries there will be no fuse in the plug
to offer it. If a device is put on the market in one EU country, then it
must be safe to sell it in all of them.

The flex needs fault protection. In the UK you can't rely on the
circuit's MCB / fuse to provide that, since it will typically be a 20 or
32A circuit (a 32A MCB needs at least 160A of fault current to ensure
disconnection via its "instant" magnetic response). Hence the need for
the plug fuse. A 13A plug fuse is quite capable of giving adequate fault
protection to a flex with a lower nominal continuous current rating. The
nominal current rating is based on maintaining conductor temperatures at
70 degrees or below, during long term sustained loads, and while able to
cool by natural means. This has little or no relevance to the same flex
under fault conditions where it is experiencing adiabatic heating due to
several hundred amps of fault current, and terminal conductor
temperatures of significantly more than 70 deg C are acceptable.

Could I suggest if you want to carry on discussing this further that you
try and make an effort to comprehend the different types of protection
that fuses and MCBs provide?

You're assuming a dead short in the appliance.

That's correct - its the proper definition of a "fault current".

This has nothing to do with "rules" or elf'n'safety, and everything to
do with really quite basic physics.

[1] Some very old appliances (i.e. pre 70s) designed just for the UK
market, may be reliant on a plug fuse for overload protection as well.
With these it is important that you use the manufacturers recommended
fuse.

So, why are there so many 3A and 5A fuses in the shops?

See [1] above. Also the same fuses can be used in places other than
plugs (FCUs for example), and for purposes other than fault protecting a
flex.


--
Cheers,

John.

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

On Wed, 03 Apr 2013 22:37:05 +0100, John Rumm wrote:

On 03/04/2013 22:27, Major Scott wrote:
On Wed, 03 Apr 2013 22:24:35 +0100, John Rumm
wrote:

On 03/04/2013 20:29, Major Scott wrote:
On Wed, 03 Apr 2013 20:21:55 +0100, John Rumm
wrote:

On 03/04/2013 15:41, Major Scott wrote:






Which (if you had any functional understanding of the issues) would
make
you far more concerned about having suitably short disconnection times
under fault conditions than prattling on about socket current ratings.

And elsewhere in the thread people are saying it's ok to protect a
device with a 3A flex with a 13A fuse!!!!

No, they are saying its ok to "protect" a 3A flex with a 13A fuse... a
subtle by very significant difference. The protection that is being
discussed (and the *only* one that matters with modern[1] appliances) is
fault protection.

If a device needs overload protection, then it must be built into the
device itself, since in most countries there will be no fuse in the plug
to offer it. If a device is put on the market in one EU country, then it
must be safe to sell it in all of them.

The flex needs fault protection. In the UK you can't rely on the
circuit's MCB / fuse to provide that, since it will typically be a 20 or
32A circuit (a 32A MCB needs at least 160A of fault current to ensure
disconnection via its "instant" magnetic response). Hence the need for
the plug fuse. A 13A plug fuse is quite capable of giving adequate fault
protection to a flex with a lower nominal continuous current rating. The
nominal current rating is based on maintaining conductor temperatures at
70 degrees or below, during long term sustained loads, and while able to
cool by natural means. This has little or no relevance to the same flex
under fault conditions where it is experiencing adiabatic heating due to
several hundred amps of fault current, and terminal conductor
temperatures of significantly more than 70 deg C are acceptable.

Could I suggest if you want to carry on discussing this further that you
try and make an effort to comprehend the different types of protection
that fuses and MCBs provide?

You're assuming a dead short in the appliance.

That's correct - its the proper definition of a "fault current".

And if the short isn't a dead short? Wire melts.

This has nothing to do with "rules" or elf'n'safety, and everything to
do with really quite basic physics.

[1] Some very old appliances (i.e. pre 70s) designed just for the UK
market, may be reliant on a plug fuse for overload protection as well.
With these it is important that you use the manufacturers recommended
fuse.

So, why are there so many 3A and 5A fuses in the shops?

See [1] above. Also the same fuses can be used in places other than
plugs (FCUs for example), and for purposes other than fault protecting a
flex.

I prefer the fuse to be the weakest link.

--
Hickory dickory dock, three mice ran up the clock. The clock struck one, and the others got away with minor injuries.

On 01/04/2013 23:53, Alexander Lamaison wrote:
Tim Watts writes:

On Monday 01 April 2013 20:14 Major Scott wrote in uk.d-i-y:

On Mon, 01 Apr 2013 18:31:04 +0100, Tim Watts
wrote:


A double socket is rated at 20A max total

Surely there would be thousands of people plugging in two 3kW loads and
melting them.....


Apparantly not.

I'm sure Tim's right simply because I've seen the 20A quoted so many
times. But I'd love to know where it comes from. Is this figure in BS
1363?

Alex

I know for a fact ('cos I prepared the data sheets for them twenty odd
years ago) that Volex 9000 range 2-gang sockets were rated at (and it
was moulded into the back of the faceplate) 29A. If I could be bothered
unscrewing one from the wall, I could take a picture, but I can't be
bothered going that far just now!

SteveW

On 03/04/2013 22:28, Major Scott wrote:

I've seen a 5A fuse protecting a 2A cable which got damaged in the
middle by crushing. The cable melted.


So the cable did not have adequate fault protection... Now you need to
asses why.

Off you go...

Refer to the trip response curve for a BS1362 fuse.

Refer to Table 41.3 and consider what effect the circuit size in
question could have on achieving adequate fault current.

What size (CSA) was this "2A" flex? Since 0.5mm^2 is the smallest used
these days (and that would be for a nominal 3A flex), it would suggest
something less than that - what was it?

What was the circuit loop impedance at the socket in question? If that
was out of spec, then it will also negate fault protection further
downstream (another reason why we care about disconnection times).

What was the loop impedance at the appliance end of the flex? (modern
appliances using thin flexes also typically use very short amounts of
them so as to limit their contribution to the overall loop impedance).




--
Cheers,

John.

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

On 03/04/2013 21:58, Major Scott wrote:
On Wed, 03 Apr 2013 21:55:10 +0100, John Rumm

Or imagine your appliance used in Germany, 16A MCB at the circuit
origin, no fuse in the plug at all, same "less than 13A capable"
flex.

Yet it all still works and fails safe, how can that be?

I do not ever put a 13A fuse in a table lamp with a 3A cord, that's
just
stupid. Why do you think there are 3A fuses in shops?

Explain how you think it works in countries other than the UK...

Their safety isn't as good as ours.

Try again, that does not answer the question....

You asked how it worked. Of course it will work, it just won't protect
well against fire.

Your statement is self contradictory. If it works (i.e. disconnects
sufficiently quickly under fault conditions), then it by definition
protects against any fire caused by those conditions.


--
Cheers,

John.

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

On Wed, 03 Apr 2013 22:54:17 +0100, SteveW wrote:

On 01/04/2013 23:53, Alexander Lamaison wrote:
Tim Watts writes:

On Monday 01 April 2013 20:14 Major Scott wrote in uk.d-i-y:

On Mon, 01 Apr 2013 18:31:04 +0100, Tim Watts
wrote:


A double socket is rated at 20A max total

Surely there would be thousands of people plugging in two 3kW loads and
melting them.....


Apparantly not.

I'm sure Tim's right simply because I've seen the 20A quoted so many
times. But I'd love to know where it comes from. Is this figure in BS
1363?

Alex

I know for a fact ('cos I prepared the data sheets for them twenty odd
years ago) that Volex 9000 range 2-gang sockets were rated at (and it
was moulded into the back of the faceplate) 29A. If I could be bothered
unscrewing one from the wall, I could take a picture, but I can't be
bothered going that far just now!

Volex are a quality item :-)

--
An actor works all his life to gain recognition.
He makes guest appearances, spends a lot for publicity people and agents etc.
Then, when he finally becomes well known, he complains he cannot go out in public anymore.

On Wed, 03 Apr 2013 23:02:21 +0100, John Rumm wrote:

On 03/04/2013 22:28, Major Scott wrote:

I've seen a 5A fuse protecting a 2A cable which got damaged in the
middle by crushing. The cable melted.


So the cable did not have adequate fault protection... Now you need to
asses why.

Off you go...

Refer to the trip response curve for a BS1362 fuse.

Refer to Table 41.3 and consider what effect the circuit size in
question could have on achieving adequate fault current.

What size (CSA) was this "2A" flex? Since 0.5mm^2 is the smallest used
these days (and that would be for a nominal 3A flex), it would suggest
something less than that - what was it?

What was the circuit loop impedance at the socket in question? If that
was out of spec, then it will also negate fault protection further
downstream (another reason why we care about disconnection times).

What was the loop impedance at the appliance end of the flex? (modern
appliances using thin flexes also typically use very short amounts of
them so as to limit their contribution to the overall loop impedance).

Or more simply, put a 2A fuse on 2A cable.

--
I learnt so much from my mistakes I think I'll make another.

On Wed, 03 Apr 2013 23:06:37 +0100, John Rumm wrote:

On 03/04/2013 21:58, Major Scott wrote:
On Wed, 03 Apr 2013 21:55:10 +0100, John Rumm



Explain how you think it works in countries other than the UK...

Their safety isn't as good as ours.

Try again, that does not answer the question....

You asked how it worked. Of course it will work, it just won't protect
well against fire.

Your statement is self contradictory. If it works (i.e. disconnects
sufficiently quickly under fault conditions), then it by definition
protects against any fire caused by those conditions.

I meant the electrical device functions.

--
If the Pope goes #2, does that make it "Holy ****"?

On 03/04/2013 21:57, Major Scott wrote:
On Wed, 03 Apr 2013 21:52:01 +0100, John Rumm
wrote:

On 03/04/2013 15:43, Major Scott wrote:
On Tue, 02 Apr 2013 22:22:36 +0100, John Rumm
wrote:

On 02/04/2013 19:43, Major Scott wrote:
On Tue, 02 Apr 2013 19:06:01 +0100, Tim Watts
wrote:

On Tuesday 02 April 2013 18:48 Major Scott wrote in uk.d-i-y:



The you should probably ask your electricy company for a 150A supply
depending of whether you have an electric shower and cooker.

And a road with 100 houses should be supplied with 5000A 3 phase
cables.

etc etc.

No, it's fine as long as there is adequate protection. The
electricity
board assumes I will never use more than 100 amps. But if I did, the
fuse next to the meter would blow.

Unlikely on both counts...

They are assuming you will use an average of around 8A

Your fuse won't blow at 100A (unless its a 40A one)

You know what I mean, obviously I can have surges.

Would you call 150A for an hour a "surge"?

(because that won't blow your 100A fuse either...)

It should.

If it should, then it would. However since there is no reason why it
"should", it doesn't!

Why call it a 100A fuse if you can use way more than that
indefinitely?

You tell me.

Once you understand why, you will find many of your other
misunderstandings will clear up.

I know a woman who melted a 4 way extension strip with two tumble driers
and 2 washing machines. Some 13A fuse that was.....

Some 13A fuses will carry 20A indefinitely. Many 4 way strips are not of
adequate construction quality to withstand even that (hence why lots are
getting rebranded as 10A max total load devices)





--
Cheers,

John.

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

On Wed, 03 Apr 2013 23:34:27 +0100, John Rumm wrote:

On 03/04/2013 21:57, Major Scott wrote:
On Wed, 03 Apr 2013 21:52:01 +0100, John Rumm
wrote:

On 03/04/2013 15:43, Major Scott wrote:
On Tue, 02 Apr 2013 22:22:36 +0100, John Rumm
wrote:

On 02/04/2013 19:43, Major Scott wrote:




Unlikely on both counts...

They are assuming you will use an average of around 8A

Your fuse won't blow at 100A (unless its a 40A one)

You know what I mean, obviously I can have surges.

Would you call 150A for an hour a "surge"?

(because that won't blow your 100A fuse either...)

It should.

If it should, then it would. However since there is no reason why it
"should", it doesn't!

So you can tell by the number on the side what it does.

Why call it a 100A fuse if you can use way more than that
indefinitely?

You tell me.

Once you understand why, you will find many of your other
misunderstandings will clear up.

Because people like to make things more complcated than they have to be.

I know a woman who melted a 4 way extension strip with two tumble driers
and 2 washing machines. Some 13A fuse that was.....

Some 13A fuses will carry 20A indefinitely. Many 4 way strips are not of
adequate construction quality to withstand even that (hence why lots are
getting rebranded as 10A max total load devices)

It's only logical to have a strip that says it will take 13A outlast a fuse that says 13A (which is what is supplied in the little container at the end of it).

There were only two sockets in the room, I gave her two new strips and told her to put one washer and one drier on each.

--
Can fat people go skinny-dipping?

On 03/04/2013 22:15, Adam Funk wrote:
On 2013-04-03, John Rumm wrote:

Bzzzzrt Is the wrong answer...

Now think a bit harder - all the information has been posted for you.

Imagine a table lamp, "3A flex", 13A fuse?

Or look at the IEC power lead in the back of your computer.... plenty of
those with 13A fuses - the cable is not 1.5mm^2 though.

Or imagine your appliance used in Germany, 16A MCB at the circuit
origin, no fuse in the plug at all, same "less than 13A capable" flex.

Hang on, it's dogma here that British wiring is vastly superior to
everything else, & that once you plug things in in foreign countries,
all bets are off & you're dicing with death.

Its a fairly safe bet that its generally superior to most other
countries (and our accident rates would back that up), but that is not
to say that every aspect of other systems is inferior.

If you take an old appliance that was not designed for general sale in
other EU countries, then indeed all bets are off. However for anything
more recent, it will have a flex CSA (e.g. usually 0.75mm^2 or more) and
length selected by its designers (often under 1.8m) such that even a 16A
MCB will offer fault protection.

If the device itself needs overload protection then it will need to be
built in to it.

Yet it all still works and fails safe, how can that be?

OK, seriously, is it impossible or just very unlikely for a portable
appliance to develop a fault (not a dead short) that will present a
fire hazard without blowing the 13 A fuse in the plug?

Nothing is impossible, but in general very unlikely.

If you ignore the cases where the appliance has a plausible overload
scenario, which could cause it to draw an abnormal current for an
extended time (i.e. those which mandate it should include its own
overload protection), we are really interested in are the hard faults
that result from cable damage etc. Most of the typical ones will be a
hard short or near enough, and should allow enough fault current to flow
to activate the protective device. But, there will also be a very small
chance of getting a fault that is borderline - what happens then will
depend on other factors.

Why do we need 1, 3, 5, & 10 A plug fuses?

There are more uses for BS1362 fuses than just in plugs. Note also, that
on old UK targeted appliances, they may well require external overload
protection, and may also expect the plug fuse to provide it. So for
those you will have to use an appropriate fuse.

Its also good practice to match the fuse to the load in some cases since
it will reduce the let through energy in the event of a blow. But as an
equipment designer you also need to recognise that fuses are user
changeable, and more importantly, the ratings interchangeable. Hence
having a 13A fuse stuck in is a foreseeable circumstance, that you may
as well just deal with.

The same fuses are also used in other circumstances. Devices that are
designed to be hard wired, may still stipulate external fused protection
at say 3A. So a 3A fuse in a FCU would be the way to go.

--
Cheers,

John.

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

On 03/04/2013 23:14, Major Scott wrote:
On Wed, 03 Apr 2013 22:54:17 +0100, SteveW
wrote:

On 01/04/2013 23:53, Alexander Lamaison wrote:
Tim Watts writes:

On Monday 01 April 2013 20:14 Major Scott wrote in uk.d-i-y:

On Mon, 01 Apr 2013 18:31:04 +0100, Tim Watts
wrote:


A double socket is rated at 20A max total

Surely there would be thousands of people plugging in two 3kW loads
and
melting them.....


Apparantly not.

I'm sure Tim's right simply because I've seen the 20A quoted so many
times. But I'd love to know where it comes from. Is this figure in BS
1363?

Alex

I know for a fact ('cos I prepared the data sheets for them twenty odd
years ago) that Volex 9000 range 2-gang sockets were rated at (and it
was moulded into the back of the faceplate) 29A. If I could be bothered
unscrewing one from the wall, I could take a picture, but I can't be
bothered going that far just now!

Volex are a quality item :-)

20 odd years ago certainly... whether the modern ones are as good is
another question.


--
Cheers,

John.

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

On 2013-04-03, John Rumm wrote:

No, they are saying its ok to "protect" a 3A flex with a 13A fuse... a
subtle by very significant difference. The protection that is being
discussed (and the *only* one that matters with modern[1] appliances) is
fault protection.

If a device needs overload protection, then it must be built into the
device itself, since in most countries there will be no fuse in the plug
to offer it. If a device is put on the market in one EU country, then it
must be safe to sell it in all of them.

The flex needs fault protection. In the UK you can't rely on the
circuit's MCB / fuse to provide that, since it will typically be a 20 or
32A circuit (a 32A MCB needs at least 160A of fault current to ensure
disconnection via its "instant" magnetic response). Hence the need for
the plug fuse. A 13A plug fuse is quite capable of giving adequate fault
protection to a flex with a lower nominal continuous current rating. The
nominal current rating is based on maintaining conductor temperatures at
70 degrees or below, during long term sustained loads, and while able to
cool by natural means. This has little or no relevance to the same flex
under fault conditions where it is experiencing adiabatic heating due to
several hundred amps of fault current, and terminal conductor
temperatures of significantly more than 70 deg C are acceptable.
....
[1] Some very old appliances (i.e. pre 70s) designed just for the UK
market, may be reliant on a plug fuse for overload protection as well.
With these it is important that you use the manufacturers recommended fuse.

That answers my question too.

On 2013-04-03, John Rumm wrote:

On 03/04/2013 22:28, Major Scott wrote:

I've seen a 5A fuse protecting a 2A cable which got damaged in the
middle by crushing. The cable melted.


So the cable did not have adequate fault protection... Now you need to
asses why.

typo of the week prize

On Thu, 04 Apr 2013 09:48:00 +0100, Adam Funk wrote:

On 2013-04-03, John Rumm wrote:

On 03/04/2013 22:28, Major Scott wrote:

I've seen a 5A fuse protecting a 2A cable which got damaged in the
middle by crushing. The cable melted.


So the cable did not have adequate fault protection... Now you need to
asses why.

typo of the week prize

That's a very big typo, even in those jeans.

--
With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion. -- Steven Weinberg