In article , John
Rumm writes

http://s833.beta.photobucket.com/use...erfeitFuse.mp4.
html

"We're sorry, we cannot find the page you requested."

http://www.bs1363.org.uk/counterfeit_fuse.mpeg

wow. Must have filled it with gunpowder rather than sand.

--
(\_/)
(='.'=)
(")_(")

In article , John
Rumm writes

(if the circuit were protected by a BS3036 rewireable fuse, or the
circuit a tad out of spec, the flex longer or thinner etc then the fuse
in the plug would be essential).

And this is part of the reason why appliance flexes are so short
nowadays: not only is the manufacturer saving a few pennies but they're
ensuring the flex is short enough with low enough resistance for a fault
current to blow the 13A fuse in the plug.

--
(\_/)
(='.'=)
(")_(")

"David Robinson" wrote in message
...
Not my question, or belief, but found here...

http://forums.digitalspy.co.uk/showthread.php?t=1755197


Is there a counter-argument?


Just to note that I've just replaced the 5A fuse in an extension lead for
the second time in a week.
Rated 4A coiled and 5A uncoiled.
We use it for lights but passing builders tend to plug anything into
anything.
So yes, the fuse does protect the cable :-)

--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

In article , Frank Erskine
writes

I don't know whether or not "intermediate" BS1362 fuses such as 5A or
7A are still available.

Pretty sure 5A is still commonly available.

The RS catalogue does BS1362 fuses in 1A, 2A, 3A, 5A, 7A, 10A and 13A.

In fact, was there not also a 1A BS1362 fuse, used for clock plugs,
but not shaver adaptors (or was it the other way round?)?

In clock plugs, yes, 1A fuses are (were) common. Clocks used to be
connected with what was essentially bell wire.

For myself, I fit 3, 5 or 13A depending on what is appropriate for the
load. 3A for things like lamps, 5A for stuff like PCs and TVs, 13A for
washing machine, fridge/freezer, dishwasher, etc.

I fitted a 1A fuse in the plug for something recently, buggered if I can
remember what it was though. Something like christmas tree lights IIRC.

--
(\_/)
(='.'=)
(")_(")

On 08/11/2012 12:51, wrote:
On Thursday, November 8, 2012 10:46:10 AM UTC, John Rumm wrote:
On 08/11/2012 07:52, harry wrote:
On Nov 7, 10:35 pm, John Rumm
wrote:
On 07/11/2012 20:20, Graham. wrote:
On Wed, 7 Nov 2012 10:40:34 -0800 (PST), David Robinson
wrote:



Not all faults are dead shorts. Transformer overheat/burnout
for example.

For the purposes of this discussion they are (its in the definition
of "fault current")

Welcome to the strange world of Aurthur Brown. The wiring regs use
'fault current' to specifically mean a dead short, but obviously in
the real world appliance faults occur that produce current (fault
current by definition) that covers the full range from a smallish
increase than only overheats a motor to a dead short.

Indeed. However the wiring regs separate these out into overload and
fault since they need to be treated separately.

Introducing a
narrow perspective definition that applies specifically to wiring and
using it outside of where it makes good sense is not productive, and

Except in this case we are not using it outside. The link the OP
referred to was a very specific question about whether a small
electronic device can be adequately "protected" by a 13A fuse. The
answer to which is yes. The protection that the fuse is there to offer
is to limit the effects of fault current - i.e. stopping the mains lead
bursting into flames, vaporising and spewing hot metal and plastic about
the place etc when someone sticks a metal chair leg through it. Once you
can demonstrate that you have achieved that level of protection, then
your job (and that of the fuse in the plug) is done.

This is a completely separate issue from minimising damage to the device
itself because some internal motor got latched on when it should not
have, and its now sucking more power than it ought. Yes that is a
"fault" in the device, and that may result in overcurrent (wiring regs
use of the term). If its a problem, then the designer can do something
about it.

insisting it must mean that elsewhere is illogical. In the world of
electronics (which many appliances are) fault current does not
usually mean a dead short across the mains.

True, but not relevant to the point under discussion.

If you want to protect electronics you are designing now from damage
resulting from overload, then you need a fuse (or thermal cutout etc).
However you can't rely on the one in the plug, since outside the UK it
won't be there.

Transformers are unlikely to be able to present any sustained load
above their design maximum for long - the wire size on their
primary winding will typically be *significantly* thinner than that
of the supply flex.

Not all equipment has internal fuses.

If it needs overload protection then it is required to have its
own protection.

In practice not all has, particularly old appliances

Remember in most markets, protection via a plug fuse is not an
option.

Old UK appliances were typically designed for only the UK market

Indeed. And for those, a lower rating fuse may be required in the plug.

Don't confuse the situation as it applies to fault current protection
for the flex on a new device one is putting onto the market in the EU
now, with old kit built to different requirements and standards.

Also don't assume that just because a 13A fuse will meet the fundamental
requirement for fault protection on new kit that there is no benefit you
using a lower value fuse in some cases. There might be.

3Kw/13a of sustained energy in an electronic device/small
electric motor could start a nice little fire.

Which would be an overload and not a fault. If there is a
plausible overload scenario, then the device in question must
include its own protection.

But in practice a fair few don't. There are still significant numbers
of old electrical goods in use spanning the range from pre-95 to
1920s. And not all new goods meet the standards legally required of
them.

As I said, in these cases if the maker said the appliance must be
protected by a 3A fuse then so be it. If they designed it to rely on a
3A fuse in a plug, that is fine, use one and not a 13A. They would not
be able to do it now (for a product to be marketed internationally) but
it does not mean it did not happen in the past.

Fault current protection is a minimum requirement - something that must
be taken into account and protection put in place for. None of that
precludes doing more than the minimum.




--
Cheers,

John.

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

On 08/11/2012 13:48, whisky-dave wrote:

A Dell PC with a 5A fuse in the plug

That seems OK as few computers would exceed 1kw but if that lead was
used as a kettle lead.....

The irony that has been highlighted before, the one thing that what many
people refer to as a "kettle lead" won't fit, is a kettle!

(i.e. an IEC cold condition connector won't go into an IEC hot condition
appliance).

A Cisco router with a 10A fuse

No idea perhaps they had a lot of 10Amp fuses spare I have, I think
they are black, 13Amp brown and 3A red.

IIRC, all fuses that are not 3 or 13A are required to be black now...

A Brother laser printer with 13A fuse.

In the days ofm teh first laser printers they took quite a heaft
startup current, in fact you shouldn;t put laswer printers on sureg
protection blaocks either.

They are fine on just a normal surge protected supply - but they are not
usually put onto UPS supplies. (many UPSs will have a dedicated surge
suppressed outlet that is not maintained during mains interruption for
the purposes of powering stuff like laser printers)

Not sur eif it's still true as I can't
believe the modern USB laserpriners would need a high startup
cutrrent....

Modern ones can be worse rather than better. Old ones tended to heat the
fuser and keep it hot. They might have a long startup time, but then
once hot, were ready to go. More energy efficient ones will use "instant
on" fusees, but these may require higher short term currents to minimise
the delay in printing the first page.


--
Cheers,

John.

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

On 08/11/2012 13:53, Mike Tomlinson wrote:
In article , John
Rumm writes

http://s833.beta.photobucket.com/use...erfeitFuse.mp4.
html

"We're sorry, we cannot find the page you requested."

http://www.bs1363.org.uk/counterfeit_fuse.mpeg

wow. Must have filled it with gunpowder rather than sand.

Na, just air...

Shows you want a fault current (wiring regs meaning) can do!


--
Cheers,

John.

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

On 08/11/2012 13:57, Mike Tomlinson wrote:
In article , John
Rumm writes

(if the circuit were protected by a BS3036 rewireable fuse, or the
circuit a tad out of spec, the flex longer or thinner etc then the fuse
in the plug would be essential).

And this is part of the reason why appliance flexes are so short
nowadays: not only is the manufacturer saving a few pennies but they're
ensuring the flex is short enough with low enough resistance for a fault
current to blow the 13A fuse in the plug.

or more likely needing to be short enough to open a 16A MCB (that and
being cheapskates!)

(short leads on power tools get on my tits!)


--
Cheers,

John.

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

On Thursday, November 8, 2012 2:59:37 PM UTC, John Rumm wrote:
On 08/11/2012 13:57, Mike Tomlinson wrote:

In article , John

Rumm writes



(if the circuit were protected by a BS3036 rewireable fuse, or the

circuit a tad out of spec, the flex longer or thinner etc then the fuse

in the plug would be essential).



And this is part of the reason why appliance flexes are so short

nowadays: not only is the manufacturer saving a few pennies but they're

ensuring the flex is short enough with low enough resistance for a fault

current to blow the 13A fuse in the plug.



or more likely needing to be short enough to open a 16A MCB (that and

being cheapskates!)



(short leads on power tools get on my tits!)

Well that's the problem with long lead they can reach tits ;-)






--

Cheers,



John.



/================================================== ===============\

| Internode Ltd - http://www.internode.co.uk |

|-----------------------------------------------------------------|

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

\================================================= ================/

On 08/11/2012 00:47, Martin Crossley wrote:


It was around the time the voltages were harmonised at 230V, flexes were
marked HAR and CE marking came in.
1995?


I remember the ads now Har, Har, Harmony... :-)

Never noticed that on a flex - only CE and other markings.

--
Rod

In message , Mike Tomlinson
writes
For myself, I fit 3, 5 or 13A depending on what is appropriate for the
load. 3A for things like lamps, 5A for stuff like PCs and TVs, 13A for
washing machine, fridge/freezer, dishwasher, etc.
Snip

My approach too. They can argue about the semantics as much as they like
but to me it make sense to have the minimum fuse necessary and also not
to rely on the safety device as an inherent part of the design.
--
bert

On Thursday, November 8, 2012 2:44:39 PM UTC, John Rumm wrote:
On 08/11/2012 12:51, wrote:
On Thursday, November 8, 2012 10:46:10 AM UTC, John Rumm wrote:
On 08/11/2012 07:52, harry wrote:
On Nov 7, 10:35 pm, John Rumm
wrote:
On 07/11/2012 20:20, Graham. wrote:
On Wed, 7 Nov 2012 10:40:34 -0800 (PST), David Robinson
wrote:


Not all faults are dead shorts. Transformer overheat/burnout
for example.

For the purposes of this discussion they are (its in the definition
of "fault current")

Welcome to the strange world of Aurthur Brown. The wiring regs use
'fault current' to specifically mean a dead short, but obviously in
the real world appliance faults occur that produce current (fault
current by definition) that covers the full range from a smallish
increase than only overheats a motor to a dead short.
Indeed. However the wiring regs separate these out into overload and
fault since they need to be treated separately.
Introducing a
narrow perspective definition that applies specifically to wiring and
using it outside of where it makes good sense is not productive, and
Except in this case we are not using it outside. The link the OP
referred to was a very specific question about whether a small
electronic device can be adequately "protected" by a 13A fuse. The
answer to which is yes. The protection that the fuse is there to offer
is to limit the effects of fault current - i.e. stopping the mains lead
bursting into flames, vaporising and spewing hot metal and plastic about
the place etc when someone sticks a metal chair leg through it. Once you
can demonstrate that you have achieved that level of protection, then
your job (and that of the fuse in the plug) is done.
This is a completely separate issue from minimising damage to the device
itself because some internal motor got latched on when it should not
have, and its now sucking more power than it ought. Yes that is a
"fault" in the device, and that may result in overcurrent (wiring regs
use of the term). If its a problem, then the designer can do something
about it.
insisting it must mean that elsewhere is illogical. In the world of
electronics (which many appliances are) fault current does not
usually mean a dead short across the mains.
True, but not relevant to the point under discussion.
If you want to protect electronics you are designing now from damage
resulting from overload, then you need a fuse (or thermal cutout etc).
However you can't rely on the one in the plug, since outside the UK it
won't be there.
Transformers are unlikely to be able to present any sustained load
above their design maximum for long - the wire size on their
primary winding will typically be *significantly* thinner than that
of the supply flex.

Not all equipment has internal fuses.

If it needs overload protection then it is required to have its
own protection.

In practice not all has, particularly old appliances

Remember in most markets, protection via a plug fuse is not an
option.

Old UK appliances were typically designed for only the UK market
Indeed. And for those, a lower rating fuse may be required in the plug.
Don't confuse the situation as it applies to fault current protection
for the flex on a new device one is putting onto the market in the EU
now, with old kit built to different requirements and standards.

They're very different. It was common for old appliances to rely entirely for overload protection on the plug fuse, and often to require it to be 5A rather than 15A. It was also common to simply not consider the issue.


Also don't assume that just because a 13A fuse will meet the fundamental
requirement for fault protection on new kit that there is no benefit you
using a lower value fuse in some cases. There might be.

There often is, a 3A fuse ruptures much quicker than 13A in many fault/overload scenarios, and that can prevent fire sometimes.


3Kw/13a of sustained energy in an electronic device/small
electric motor could start a nice little fire.

Which would be an overload and not a fault. If there is a
plausible overload scenario, then the device in question must
include its own protection.

But in practice a fair few don't. There are still significant numbers
of old electrical goods in use spanning the range from pre-95 to
1920s. And not all new goods meet the standards legally required of
them.
As I said, in these cases if the maker said the appliance must be
protected by a 3A fuse then so be it. If they designed it to rely on a
3A fuse in a plug, that is fine, use one and not a 13A. They would not
be able to do it now (for a product to be marketed internationally) but
it does not mean it did not happen in the past.

I think the normal recommendations were 5A, 2A, and sometimes 1A, and later 3A. But tracking any such recommendations is unlikely to work out in many cases, and many manufacturers simply ignored the issue. Some of the safety issues were very basic, a lot didn't even have a cordgrip. I recall one relatively well regarded 1960s product that used a strip of ali foil for earthing, stapled down to connect it.


Fault current protection is a minimum requirement - something that must
be taken into account and protection put in place for. None of that
precludes doing more than the minimum.

Exactly.


NT

On Wed, 07 Nov 2012 22:44:35 +0000, John Rumm
wrote:

You want to see the bang with the counterfeit ones arriving with your
latest mains lead from China via ebay:

http://www.bs1363.org.uk/counterfeit_fuse.mpeg


Surely for fuses that should be bs1362.org.uk ?
--

Man at B&Q :
On Nov 8, 12:33*pm, The Natural Philosopher
wrote:
On 08/11/12 10:49, Man at B&Q wrote:
all short circuits are faults.

Anything else is an overload.

What a peculiar version of the english language you speak...

Lets say we have an SMPS, and due to a fault in the main 400V reservoir
on the mains side, it starts leaking several amps ...

You are saying that's not a fault?

Well, it is faulty, but in the jargon, that is not a fault current.

So, you're agreed. The jargon = a peculiar version of English.

--
Mike Barnes

On Thu, 08 Nov 2012 14:55:34 +0000, John Rumm wrote:

On 08/11/2012 13:48, whisky-dave wrote:

A Dell PC with a 5A fuse in the plug

That seems OK as few computers would exceed 1kw but if that lead was
used as a kettle lead.....

I remember having one computer which needed a 'kettle lead' with a notch
cut out of it (which may indeed be a *real* 'kettle lead' connector, but
I never did check). PSU was rated to 800W IIRC, and it was probably
running at close to that.

On Wed, 07 Nov 2012 23:43:36 -0800, harry wrote:
I think the 13a plug is the only one in the world with a fuse.

Fused plugs do exist here in the US, most often seen on Christmas tree
lights (the ones that are made here, rather than the China-built death
traps) - they have a little trapdoor in them for fuse access (US plugs
are tiny in comparison the the UK's chunk-o-rama ones :-) and a pair of
fuses that are around 10mm in length.

cheers

Jules

On Wed, 7 Nov 2012 23:57:08 -0800 (PST), harry
wrote:

On Nov 7, 11:56*pm, Frank Erskine
wrote:
On Wed, 07 Nov 2012 22:26:06 +0000, Peter Crosland
wrote:

On 07/11/2012 18:40, David Robinson wrote:
Not my question, or belief, but found here...

http://forums.digitalspy.co.uk/showthread.php?t=1755197

Is there a counter-argument?

Only the terminally stupid would use a 13A fuse when a 3A is appropriate.

In the early days of colour TV I was told by a TV engineer that the
correct plug fuse for a CTV was 7A to allow for the switch-on current
surge of the degaussing circuitry.

I don't know whether or not "intermediate" BS1362 fuses such as 5A or
7A are still available.

In fact, was there not also a 1A BS1362 fuse, used for clock plugs,
but not shaver adaptors (or was it the other way round?)?

--
Frank Erskine

There was indeed. One was physically smaller than the plug fuse. You
found them in mains electric clock connectors. Of course, you never
see mains clocks any more except as radios.
There have been all sorts of odd sizes over the years.

I have a working mains clock on the desk here, with starter and
tick/silent gismos.
The clock connecter fuse is the same size as the ones on 5A Wylex
plugs.

--
Graham.
%Profound_observation%

"David WE Roberts" wrote in message
...

"David Robinson" wrote in message
...
Not my question, or belief, but found here...

http://forums.digitalspy.co.uk/showthread.php?t=1755197


Is there a counter-argument?


Just to note that I've just replaced the 5A fuse in an extension lead for
the second time in a week.
Rated 4A coiled and 5A uncoiled.
We use it for lights but passing builders tend to plug anything into
anything.
So yes, the fuse does protect the cable :-)

You are correct, but a little slower - it may go to 4A before the fuse
breaks. If current is say 1A and the fuse 3A, then the current increases for
whatever to 4A the fuse may not break so quick, but will eventually, so
giving protection. The fuses are designed for fault current, which means, as
one poster in the link stated a 3A and 13A will break as quick as each
other - on a fault.

I only scanned the link, but one poster I think was saying have all fuses
13A. So if he had a lamp with 0.25mm flex and 13A fuses he thinks he is
safe. OK on a lamp it is difficult to see how the current would be great
enough to melt the cable as the bulb would blow way before any current is
dangerous enough. They only time the current would be high enough to melt
the flex would be if there is a fault, which would be momentarily and the
fuse would then snap. I "think" that is what is he on about. He says the
13A fuse will break faster on a fault than a 3A. BTW, I recall as a kid my
sister's cheap Italian (looked good though) table lamp switch melting. It
obviously had a "fault" and" a 13A fuse. A 3A fuse would have snapped
stopping the melting, which was a fire hazard. The switch could be classed
as a part of the cable and the appliance the light bulb.

The secret? As fuses have dropped into 3A and 13A in common use (Only
specialist outlets sell anything else these days) never install flex that is
rated less than 3A and fit correct sized fuse to protect the cable. The
cable should never be rated less than the fuse.

Some fit larger rated fuses because of surge. If there is surge then fit
anti-surge fuses, not a large rated fuse.

On Thursday, November 8, 2012 2:57:26 PM UTC, John Rumm wrote:
On 08/11/2012 13:53, Mike Tomlinson wrote:
In article , John
Rumm writes

http://s833.beta.photobucket.com/use...erfeitFuse.mp4.
html

"We're sorry, we cannot find the page you requested."

http://www.bs1363.org.uk/counterfeit_fuse.mpeg

wow. Must have filled it with gunpowder rather than sand.
Na, just air...
Shows you want a fault current (wiring regs meaning) can do!


I'm not convinced. In decades past I've seen loads of fuses repaired with bits of fusewire, or worse just a thin strand of copper wire. The failure of such fuses was entirely tame, the downside was just black deposits inside the plug, requiring a new plug. I've seen plenty of glass fuses fail on mains too, and again nothing dramatic.

How could they create that clip? I suspect by bypassing the protection of both incomer fuse and CU entirely, and picking an unusually meaty (non)fuse, and passing the full 6kA through it, perhaps at above mains voltage too. It sure looks like bs to me, but not 1362.


NT

On Thursday, November 8, 2012 11:28:43 PM UTC, Jules Richardson wrote:
On Wed, 07 Nov 2012 23:43:36 -0800, harry wrote:
I think the 13a plug is the only one in the world with a fuse.
Fused plugs do exist here in the US, most often seen on Christmas tree
lights (the ones that are made here, rather than the China-built death
traps) - they have a little trapdoor in them for fuse access (US plugs
are tiny in comparison the the UK's chunk-o-rama ones :-) and a pair of
fuses that are around 10mm in length.
cheers
Jules

Fusing on the neutral pole was banned here eons ago. A blown neutral fuse causes a faulty appliance to look dead, but be live.

A 10mm long fuse must have too low a breaking capacity to cope with more current than the breaker would act on. With the US fixed wiring system's lowish current breakers this shouldn't be a problem though.


NT

On Friday, November 9, 2012 8:37:43 AM UTC, Doctor Drivel wrote:
"David WE Roberts" wrote in message
...
"David Robinson" davidrobinson wrote in message
...

Not my question, or belief, but found here...

http://forums.digitalspy.co.uk/showthread.php?t=1755197


Is there a counter-argument?

Just to note that I've just replaced the 5A fuse in an extension lead for
the second time in a week.
Rated 4A coiled and 5A uncoiled.
We use it for lights but passing builders tend to plug anything into
anything.
So yes, the fuse does protect the cable :-)

You are correct, but a little slower - it may go to 4A before the fuse
breaks. If current is say 1A and the fuse 3A, then the current increases for
whatever to 4A the fuse may not break so quick, but will eventually, so
giving protection. The fuses are designed for fault current, which means, as
one poster in the link stated a 3A and 13A will break as quick as each
other - on a fault.
I only scanned the link, but one poster I think was saying have all fuses
13A. So if he had a lamp with 0.25mm flex and 13A fuses he thinks he is
safe. OK on a lamp it is difficult to see how the current would be great
enough to melt the cable as the bulb would blow way before any current is
dangerous enough. They only time the current would be high enough to melt
the flex would be if there is a fault, which would be momentarily and the
fuse would then snap. I "think" that is what is he on about. He says the
13A fuse will break faster on a fault than a 3A. BTW, I recall as a kid my
sister's cheap Italian (looked good though) table lamp switch melting. It
obviously had a "fault" and" a 13A fuse. A 3A fuse would have snapped
stopping the melting, which was a fire hazard. The switch could be classed
as a part of the cable and the appliance the light bulb.
The secret? As fuses have dropped into 3A and 13A in common use (Only
specialist outlets sell anything else these days) never install flex that is
rated less than 3A and fit correct sized fuse to protect the cable. The
cable should never be rated less than the fuse.
Some fit larger rated fuses because of surge. If there is surge then fit
anti-surge fuses, not a large rated fuse.

You're the only person I've ever heard describe pound shops as specialist outlets.

Nurse!


NT

On Thursday, November 8, 2012 8:14:18 PM UTC, bert wrote:
In message , Mike Tomlinson

writes

For myself, I fit 3, 5 or 13A depending on what is appropriate for the

load. 3A for things like lamps, 5A for stuff like PCs and TVs, 13A for

washing machine, fridge/freezer, dishwasher, etc.

Snip



My approach too. They can argue about the semantics as much as they like

but to me it make sense to have the minimum fuse necessary and also not

to rely on the safety device as an inherent part of the design.

True but how do you calculate the minimum fuse necessary, it's not always that easy.



--

bert

On Friday, November 9, 2012 8:37:43 AM UTC, Doctor Drivel wrote:
"David WE Roberts" wrote in message

...



"David Robinson" wrote in message

...

Not my question, or belief, but found here...



http://forums.digitalspy.co.uk/showthread.php?t=1755197





Is there a counter-argument?





Just to note that I've just replaced the 5A fuse in an extension lead for

the second time in a week.

Rated 4A coiled and 5A uncoiled.

We use it for lights but passing builders tend to plug anything into

anything.

So yes, the fuse does protect the cable :-)



You are correct, but a little slower - it may go to 4A before the fuse

breaks. If current is say 1A and the fuse 3A, then the current increases for

whatever to 4A the fuse may not break so quick, but will eventually, so

giving protection. The fuses are designed for fault current, which means, as

one poster in the link stated a 3A and 13A will break as quick as each

other - on a fault.

really ?

A 3amp fuse will break as quick as a 13amp will iof you pass 15 amps through it I don;t think so.



I only scanned the link, but one poster I think was saying have all fuses

13A. So if he had a lamp with 0.25mm flex and 13A fuses he thinks he is

safe. OK on a lamp it is difficult to see how the current would be great

enough to melt the cable as the bulb would blow way before any current is

dangerous enough.

Unless somethijng shorts circuits the buld of course.

They only time the current would be high enough to melt

the flex would be if there is a fault, which would be momentarily and the

fuse would then snap.

After a set time depending on the curretn flowing and the lengh of time.

I "think" that is what is he on about. He says the

13A fuse will break faster on a fault than a 3A. BTW, I recall as a kid my

sister's cheap Italian (looked good though) table lamp switch melting. It

obviously had a "fault" and" a 13A fuse. A 3A fuse would have snapped

stopping the melting,

fuses don;t snap they burn out.


which was a fire hazard. The switch could be classed

as a part of the cable and the appliance the light bulb.

could be if it were on the cable.




The secret? As fuses have dropped into 3A and 13A in common use (Only

specialist outlets sell anything else these days) never install flex that is

rated less than 3A

Unless yuo need to.

and fit correct sized fuse to protect the cable. The

cable should never be rated less than the fuse.



Some fit larger rated fuses because of surge. If there is surge then fit

anti-surge fuses, not a large rated fuse.

That is not correct, you can't buy mains plug fuses in anti-surge.
Those sort are commom as internal fuses for protecting the equipment rahter than the cable.

A while ago I brought some 20mm 32ma slow-blow for a piece of euipment.

In article ,
whisky-dave writes

True but how do you calculate the minimum fuse necessary, it's not always that
easy.

Yes it is, you look at the appliance rating plate and if it's in watts
not amps, apply Ohm's law.

--
(\_/)
(='.'=)
(")_(")

On Friday, November 9, 2012 1:58:11 PM UTC, Mike Tomlinson wrote:
In article ,

whisky-dave writes



True but how do you calculate the minimum fuse necessary, it's not always that

easy.



Yes it is, you look at the appliance rating plate and if it's in watts

not amps, apply Ohm's law.

So what fuse do you put in a fan that's rated at 50W a 3 amp ?
As that's what's in the fan we brought and it has been PAT tested and passed.

for me 50/230 is NOT 3
So are you saying I should put in a ~250ma fuse instead ?
As that's how I'd calculate it, but I'd put a 3 amp fuse in the plug as that's what the manufactuer did.







--

(\_/)

(='.'=)

(")_(")

In article ,
whisky-dave wrote:
On Friday, November 9, 2012 1:58:11 PM UTC, Mike Tomlinson wrote:
In article ,

whisky-dave writes



True but how do you calculate the minimum fuse necessary, it's not
always that

easy.



Yes it is, you look at the appliance rating plate and if it's in watts

not amps, apply Ohm's law.

So what fuse do you put in a fan that's rated at 50W a 3 amp ? As that's
what's in the fan we brought and it has been PAT tested and passed.

for me 50/230 is NOT 3 So are you saying I should put in a ~250ma fuse
instead ? As that's how I'd calculate it, but I'd put a 3 amp fuse in the
plug as that's what the manufactuer did.

You forgot the switch on surge. the 50w is the running power

--
From KT24

Using a RISC OS computer running v5.18

On Friday, November 9, 2012 2:37:00 PM UTC, charles wrote:
In article ,
whisky-dave wrote:
On Friday, November 9, 2012 1:58:11 PM UTC, Mike Tomlinson wrote:
In article ,
whisky-dave writes

True but how do you calculate the minimum fuse necessary, it's not
always that
easy.

Yes it is, you look at the appliance rating plate and if it's in watts
not amps, apply Ohm's law.

So what fuse do you put in a fan that's rated at 50W a 3 amp ? As that's
what's in the fan we brought and it has been PAT tested and passed.
for me 50/230 is NOT 3 So are you saying I should put in a ~250ma fuse
instead ? As that's how I'd calculate it, but I'd put a 3 amp fuse in the
plug as that's what the manufactuer did.

You forgot the switch on surge. the 50w is the running power

Exactly. There's also availability, and the fact that fuses below 3A often die of their own accord over time.


NT

En el artículo ,
whisky-dave escribió:

So are you saying I should put in a ~250ma fuse instead ?

Use your common sense.

BS1362 fuses are not available in 250ma, so a 3A fuse would be the best
choice.

As that's how I'd calculate it, but I'd put a 3 amp fuse in the plug as that's
what the manufactuer did.

There you go then.

--
(\_/)
(='.'=)
(")_(")

On 09/11/2012 13:57, Mike Tomlinson wrote:
In article ,
whisky-dave writes

True but how do you calculate the minimum fuse necessary, it's not always that
easy.

Yes it is, you look at the appliance rating plate and if it's in watts
not amps, apply Ohm's law.

I can't help thinking that it would make sense for manufacturers to
include "use a 3A plug fuse" on the rating plate. We see so many
meaningless[1] symbols identifying all the standards it claims to follow
- why not a piece of potentially useful information?

[1] I know they are not all actually meaningless, but to a large
proportion of end users of a lot of appliances, they might as well not
be there.

--
Rod

On Friday, November 9, 2012 4:23:14 PM UTC, Mike Tomlinson wrote:
En el artículo ,

whisky-dave escribió:



So are you saying I should put in a ~250ma fuse instead ?



Use your common sense.

Which would be wrong, because I as do others have to abide by the current ;-) legislation so calculating is less than half the battle.
If I wass using cvommon sense I;'d use teh lowest fuses I have which is a 1 amp, but I use management sense which means 3 amp is chosen.





BS1362 fuses are not available in 250ma,

yes I know and that's also why I said in another post ypou can;t use anit-surge

so a 3A fuse would be the best

choice.

Yep, which is NOT arrived at through a calculation which is the point.





As that's how I'd calculate it, but I'd put a 3 amp fuse in the plug as that's

what the manufactuer did.



There you go then.

yep no calculation necessary




--

(\_/)

(='.'=)

(")_(")

On Friday, November 9, 2012 2:37:00 PM UTC, charles wrote:
In article ,

whisky-dave wrote:

On Friday, November 9, 2012 1:58:11 PM UTC, Mike Tomlinson wrote:

In article ,



whisky-dave writes







True but how do you calculate the minimum fuse necessary, it's not

always that



easy.







Yes it is, you look at the appliance rating plate and if it's in watts



not amps, apply Ohm's law.



So what fuse do you put in a fan that's rated at 50W a 3 amp ? As that's

what's in the fan we brought and it has been PAT tested and passed.



for me 50/230 is NOT 3 So are you saying I should put in a ~250ma fuse

instead ? As that's how I'd calculate it, but I'd put a 3 amp fuse in the

plug as that's what the manufactuer did.



You forgot the switch on surge. the 50w is the running power

No I didn;t because I estimated that the switch on surge would be low for this type of applience well low is respect of the fuse rating.

How would you calculte the switch on surge if you needed to ?
How would you allow for this value in the fuse you choose ?.




From KT24



Using a RISC OS computer running v5.18

In article ,
whisky-dave wrote:
On Friday, November 9, 2012 2:37:00 PM UTC, charles wrote:
In article ,

whisky-dave wrote:

On Friday, November 9, 2012 1:58:11 PM UTC, Mike Tomlinson wrote:

In article ,



whisky-dave writes







True but how do you calculate the minimum fuse necessary, it's not

always that



easy.







Yes it is, you look at the appliance rating plate and if it's in
watts



not amps, apply Ohm's law.



So what fuse do you put in a fan that's rated at 50W a 3 amp ? As
that's

what's in the fan we brought and it has been PAT tested and passed.



for me 50/230 is NOT 3 So are you saying I should put in a ~250ma fuse

instead ? As that's how I'd calculate it, but I'd put a 3 amp fuse in
the

plug as that's what the manufactuer did.



You forgot the switch on surge. the 50w is the running power

No I didn;t because I estimated that the switch on surge would be low for
this type of applience well low is respect of the fuse rating.

How would you calculte the switch on surge if you needed to ? How would
you allow for this value in the fuse you choose ?.

I wouldn't calculate it. It needs to be measured. and no, I don't have
the correct meter for the job.

--
From KT24

Using a RISC OS computer running v5.18

En el artículo ,
whisky-dave escribió:

If I wass using cvommon sense I;'d use teh lowest fuses I have which is a 1 amp,
but I use management sense which means 3 amp is chosen.

If by 'management sense' you mean common sense, then we're arguing about
precisely nothing :-)

--
(\_/)
(='.'=)
(")_(")

En el artículo , polygonum
escribió:

I can't help thinking that it would make sense for manufacturers to
include "use a 3A plug fuse" on the rating plate.

I do see that sometimes, perhaps not on rating plates but in the user
manual that comes with the appliance.

It normally follows the plug wiring instructions and is worded something
along the lines of, "this appliance is supplied pre-fitted with a plug.
If it is necessary to fit your own plug, the brown wire must be
connected to the terminal coloured brown or marked L, the blue wire must
be connected to the terminal coloured blue or marked N, and the fuse
fitted must be rated at xA."

Because appliance flexes are so stupidly short nowadays and the 13A fuse
is universal (hello Mr Dyson, are you listening?), if I find myself
rewiring an appliance with a longer flex (hello Mr Dyson, I don't live
in a ****ing rabbit hutch) I fit a lower-rated fuse in the plug to allow
for the increased wire resistance and therefore lower fault current to
ensure the fuse does blow under fault conditions.

But of course, elfin safety means we have to cater for the lowest common
denominator, so it's 6" flexes and 13A fuses all round.

--
(\_/)
(='.'=)
(")_(")

On 09/11/2012 18:49, Mike Tomlinson wrote:
En el artículo , polygonum
escribió:

I can't help thinking that it would make sense for manufacturers to
include "use a 3A plug fuse" on the rating plate.

I do see that sometimes, perhaps not on rating plates but in the user
manual that comes with the appliance.

It normally follows the plug wiring instructions and is worded something
along the lines of, "this appliance is supplied pre-fitted with a plug.
If it is necessary to fit your own plug, the brown wire must be
connected to the terminal coloured brown or marked L, the blue wire must
be connected to the terminal coloured blue or marked N, and the fuse
fitted must be rated at xA."

Because appliance flexes are so stupidly short nowadays and the 13A fuse
is universal (hello Mr Dyson, are you listening?), if I find myself
rewiring an appliance with a longer flex (hello Mr Dyson, I don't live
in a ****ing rabbit hutch) I fit a lower-rated fuse in the plug to allow
for the increased wire resistance and therefore lower fault current to
ensure the fuse does blow under fault conditions.

But of course, elfin safety means we have to cater for the lowest common
denominator, so it's 6" flexes and 13A fuses all round.

Not only short - but inflexible. Well, they do flex, but they don't
drape as they should. Got several things which are a pain to use simply
because of the flex.

--
Rod

wrote:


Exactly. There's also availability, and the fact that fuses
below 3A often die of their own accord over time.

If you use a mA fuse that's only barely adequate for the load there's
voltage drop across it.

Bill

In message ,
whisky-dave writes
On Thursday, November 8, 2012 8:14:18 PM UTC, bert wrote:
In message , Mike Tomlinson

writes

For myself, I fit 3, 5 or 13A depending on what is appropriate for the

load. 3A for things like lamps, 5A for stuff like PCs and TVs, 13A for

washing machine, fridge/freezer, dishwasher, etc.

Snip



My approach too. They can argue about the semantics as much as they like

but to me it make sense to have the minimum fuse necessary and also not

to rely on the safety device as an inherent part of the design.

True but how do you calculate the minimum fuse necessary, it's not
always that easy.


Take the empirical approach
--
bert

In message ,
whisky-dave writes
On Friday, November 9, 2012 1:58:11 PM UTC, Mike Tomlinson wrote:
In article ,

whisky-dave writes



True but how do you calculate the minimum fuse necessary, it's not
always that

easy.



Yes it is, you look at the appliance rating plate and if it's in watts

not amps, apply Ohm's law.

So what fuse do you put in a fan that's rated at 50W a 3 amp ?
As that's what's in the fan we brought and it has been PAT tested and passed.

for me 50/230 is NOT 3
So are you saying I should put in a ~250ma fuse instead ?
As that's how I'd calculate it, but I'd put a 3 amp fuse in the plug as
that's what the manufactuer did.


3 amp as opposed to 5 amp or 13 amp.

--
bert

In message ,
writes
Fusing on the neutral pole was banned here eons ago.
Snip
Fusing the neutral must be one of the most brainless ideas ever.
--
bert

On Fri, 09 Nov 2012 02:57:47 -0800, meow2222 wrote:

On Thursday, November 8, 2012 11:28:43 PM UTC, Jules Richardson wrote:
On Wed, 07 Nov 2012 23:43:36 -0800, harry wrote:
I think the 13a plug is the only one in the world with a fuse.
Fused plugs do exist here in the US, most often seen on Christmas tree
lights (the ones that are made here, rather than the China-built death
traps) - they have a little trapdoor in them for fuse access (US plugs
are tiny in comparison the the UK's chunk-o-rama ones :-) and a pair of
fuses that are around 10mm in length. cheers
Jules

Fusing on the neutral pole was banned here eons ago. A blown neutral
fuse causes a faulty appliance to look dead, but be live.

Yes, it ain't necessarily a good thing :-) I had a look at a couple of
strings of Chrimbo lights kicking around in the basement, and they're
both using 3A fuses.

A 10mm long fuse must have too low a breaking capacity to cope with more
current than the breaker would act on. With the US fixed wiring system's
lowish current breakers this shouldn't be a problem though.

Well ours all seem to be rated at 15A or 20A (with a few at 30A for
things such as the cooker).

cheers

J