On 19/08/2020 00:19, Cursitor Doom wrote:
On Tue, 18 Aug 2020 16:42:03 +0100, charles
wrote:

In article ,
Dave Plowman (News) wrote:
In article ,
Scott wrote:
Most want something to work, before considering safety.

True, but I have never encountered an appliance not working due to
being fitted with a 1 amp or 2 amp fuse.

Not even a fan heater? ;-)

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

The degaussing coils created quite a surge at switch on,

That's the kind of thing that T rated fuses are for. Fitting a regular
13A in those circumstances is just plain dumb.

BS 1362 plug fuses are in effect T rated anyway - there is no quick blow
equivalent. If your CRT switch on surge will blow a 5A fuse, what other
choice did you have (given that anything other than 3, 5, & 13A was not
readily available at the time)


--
Cheers,

John.

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

In article , John
Rumm scribeth thus
On 19/08/2020 00:19, Cursitor Doom wrote:
On Tue, 18 Aug 2020 16:42:03 +0100, charles
wrote:

In article ,
Dave Plowman (News) wrote:
In article ,
Scott wrote:
Most want something to work, before considering safety.

True, but I have never encountered an appliance not working due to
being fitted with a 1 amp or 2 amp fuse.

Not even a fan heater? ;-)

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

The degaussing coils created quite a surge at switch on,

That's the kind of thing that T rated fuses are for. Fitting a regular
13A in those circumstances is just plain dumb.

BS 1362 plug fuses are in effect T rated anyway - there is no quick blow
equivalent. If your CRT switch on surge will blow a 5A fuse, what other
choice did you have (given that anything other than 3, 5, & 13A was not
readily available at the time)



Used to work years ago in a TV repair shop mainly Phillips G6, G9 and
G11 chassis sets all CRT ones never remembered having to put large fuses
in them had to wire on the mains plugs and could swear blind we only
used 5 amp ones!

They would and could blow their fuses internal ones triacs and the like
playing up..

AFAICR the degauss coils had some sort of limiter to stop a large surge
and then they had another device to get them to fade down the magnetic
field to de-mag the tube, don't ever remember them playing up either!..
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

On 19/08/2020 21:14, tony sayer wrote:
In article , John
Rumm scribeth thus
On 19/08/2020 00:19, Cursitor Doom wrote:
On Tue, 18 Aug 2020 16:42:03 +0100, charles
wrote:

In article ,
Dave Plowman (News) wrote:
In article ,
Scott wrote:
Most want something to work, before considering safety.

True, but I have never encountered an appliance not working due to
being fitted with a 1 amp or 2 amp fuse.

Not even a fan heater? ;-)

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

The degaussing coils created quite a surge at switch on,

That's the kind of thing that T rated fuses are for. Fitting a regular
13A in those circumstances is just plain dumb.

BS 1362 plug fuses are in effect T rated anyway - there is no quick blow
equivalent. If your CRT switch on surge will blow a 5A fuse, what other
choice did you have (given that anything other than 3, 5, & 13A was not
readily available at the time)



Used to work years ago in a TV repair shop mainly Phillips G6, G9 and
G11 chassis sets all CRT ones never remembered having to put large fuses
in them had to wire on the mains plugs and could swear blind we only
used 5 amp ones!

I was making a general point, but perhaps for a TV it would in most
cases be closer to say you need 5A but looking at the ratings plate and
not understanding issues like inrush, my opt to fit 3A then have
problems with seemingly random blows.

They would and could blow their fuses internal ones triacs and the like
playing up..

AFAICR the degauss coils had some sort of limiter to stop a large surge
and then they had another device to get them to fade down the magnetic
field to de-mag the tube, don't ever remember them playing up either!..

Some seemed to just place a PTC thermistor in series with the degauss
coils such that as it heats up is reduces the current through the coils.
A fairly crude solution since it then sits there running very hot most
of the time the set is on.

--
Cheers,

John.

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

On 18/08/2020 17:50, John Rumm wrote:
On 18/08/2020 16:03, wrote:
On Tuesday, 18 August 2020 15:58:52 UTC+1, John RummÂ* wrote:
On 18/08/2020 11:45, tabbypurr wrote:
On Tuesday, 18 August 2020 00:57:27 UTC+1, John RummÂ* wrote:
On 17/08/2020 23:04, tabbypurr wrote:
On Monday, 17 August 2020 22:29:49 UTC+1, Cursitor DoomÂ* wrote:

You frequently use the term "fault current" which crops up
frequently when professional electrical engineers are discussing
installations. However, for everyone else, it requires
clarification. I'm not an electrician, so I have no idea when you
use that term whether you're referring to *short circuit* current
or *earth leakage* current or something else altogether (unless you
use an example as you did above but even that's not watertight).
And then there's that lot that read this through Homeownershub -
God only knows what *they* make of it. ;-


The electrical wiring regs' meaning of 'fault' is a hard zero ohm L-N
short..

or L-E

John uses that meaning. Those of us that are more into
repairing things tend to use 'fault' to mean any failure to operate
correctly. The I with some Es seems to like to define existing terms
differently to everyone else, classic communication poor practice.

Being one who also repairs stuff, I am fully aware that the colloquial
use of "fault" is far less specific than that when used in engineering
and standards documentation for electrical systems.

No, the usage of 'fault' to mean zero ohm short only is specific to
UK wiring regs not specific to engineering.

The UK wiring regs don't use "Fault" to mean zero ohm.

"Fault Current", is a specialist English and an engineering term used
by many, not only in the UK.

AIUI fault current does mean the current resulting from a zero ohm
connection from live to not live.

No, you can have line to line fault currents (and line to neutral is
also "live to live" if one is being a pedant)

However if you are
going to have a meaningful discussion on fusing etc, it is quite
important that everyone uses a consistent set of terms when it
matters.

Good luck with that

Make up your own terms if you like, if you think it will help.

No need. 'Fault' is in widespread use to mean any failure, including
in engineering.

and "Fault Current" is not, So why use Fault if you mean Fault Current?



Coows scratching on a rural wooden post carrying HV 3-phase used to be
a common live-to-live fault.

On 18/08/2020 17:01, charles wrote:
In article ,
No Name wrote:
On 18/08/2020 16:07, John Rumm wrote:
On 18/08/2020 13:46, Dave Plowman (News) wrote:

But the idea of using lots of different fuses for plug tops is
downright stupid too - unless it was impossible to fit the wrong one.
Human nature being as it is.

That fact that stuff comes with a pre-fitted plug these days, has lead
to a generation that now no longer know how to fit one, and in many
cases probably probably don't even know what a fuse looks like.



I am old enough to remember wire colours before blue for neutral, brown
for live and green/yellow for earth became commonplace...

it was red for live, black for neutral and green for earth.....

and the fun came if you had a German made appliance. Red for earth ......


I think it still is on some German cars

On 20/08/2020 15:03, Andrew wrote:
On 18/08/2020 17:50, John Rumm wrote:
On 18/08/2020 16:03, wrote:
On Tuesday, 18 August 2020 15:58:52 UTC+1, John RummÂ* wrote:
On 18/08/2020 11:45, tabbypurr wrote:
On Tuesday, 18 August 2020 00:57:27 UTC+1, John RummÂ* wrote:
On 17/08/2020 23:04, tabbypurr wrote:
On Monday, 17 August 2020 22:29:49 UTC+1, Cursitor DoomÂ* wrote:

You frequently use the term "fault current" which crops up
frequently when professional electrical engineers are discussing
installations. However, for everyone else, it requires
clarification. I'm not an electrician, so I have no idea when you
use that term whether you're referring to *short circuit* current
or *earth leakage* current or something else altogether (unless you
use an example as you did above but even that's not watertight).
And then there's that lot that read this through Homeownershub -
God only knows what *they* make of it. ;-


The electrical wiring regs' meaning of 'fault' is a hard zero ohm
L-N
short..

or L-E

John uses that meaning. Those of us that are more into
repairing things tend to use 'fault' to mean any failure to operate
correctly. The I with some Es seems to like to define existing terms
differently to everyone else, classic communication poor practice.

Being one who also repairs stuff, I am fully aware that the
colloquial
use of "fault" is far less specific than that when used in
engineering
and standards documentation for electrical systems.

No, the usage of 'fault' to mean zero ohm short only is specific to
UK wiring regs not specific to engineering.

The UK wiring regs don't use "Fault" to mean zero ohm.

"Fault Current", is a specialist English and an engineering term used
by many, not only in the UK.

AIUI fault current does mean the current resulting from a zero ohm
connection from live to not live.

No, you can have line to line fault currents (and line to neutral is
also "live to live" if one is being a pedant)

However if you are
going to have a meaningful discussion on fusing etc, it is quite
important that everyone uses a consistent set of terms when it
matters.

Good luck with that

Make up your own terms if you like, if you think it will help.

No need. 'Fault' is in widespread use to mean any failure, including
in engineering.

and "Fault Current" is not, So why use Fault if you mean Fault Current?



Coows scratching on a rural wooden post carrying HV 3-phase used to be
a common live-to-live fault.

That sounds like it could be bad news for the cow!

--
Cheers,

John.

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

On 18/08/2020 20:57, Scott wrote:
On Tue, 18 Aug 2020 20:30:33 +0100, ARW
wrote:

On 18/08/2020 11:51, Scott wrote:
On Tue, 18 Aug 2020 10:51:29 +0100, "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
Why do you think the system was introduced with 1, 2, 3, 5, 7, 10 and
13 amp fuses unless a lower rated fuse had safety benefits?

And it failed miserably. If a fuse blows, all the vast majority will do is
replace it to get it working again. And are very unlikely to have all
those values to hand. And the spares they are likely to find, 13 amp.

Hence the current method of having wiring capable of taking out a 13 amp
fuse if there is a sort somewhere without causing a fire. And protecting
the device itself with its own fuse if needed.

IMO changing to a 2 amp fuse can only nudge safety in one direction.

Only if it is the real thing. And even them there is very little difference.

Is the counterfeit risk inversely related to amperage then?


Depends on what it is made of?

--
Adam

On Tuesday, 18 August 2020 16:30:36 UTC+1, No Name wrote:
On 18/08/2020 16:07, John Rumm wrote:
On 18/08/2020 13:46, Dave Plowman (News) wrote:

But the idea of using lots of different fuses for plug tops is downright
stupid too - unless it was impossible to fit the wrong one. Human nature
being as it is.

That fact that stuff comes with a pre-fitted plug these days, has lead
to a generation that now no longer know how to fit one, and in many
cases probably probably don't even know what a fuse looks like.



I am old enough to remember wire colours before blue for neutral, brown
for live and green/yellow for earth became commonplace...

it was red for live, black for neutral and green for earth.....

:-)

and I remember people sticking the green wire into the fuseholder in the plug. Yep, colourblind.

On Tuesday, 18 August 2020 17:50:17 UTC+1, John Rumm wrote:
On 18/08/2020 16:03, tabbypurr wrote:
On Tuesday, 18 August 2020 15:58:52 UTC+1, John Rumm wrote:
On 18/08/2020 11:45, tabbypurr wrote:
On Tuesday, 18 August 2020 00:57:27 UTC+1, John Rumm wrote:
On 17/08/2020 23:04, tabbypurr wrote:
On Monday, 17 August 2020 22:29:49 UTC+1, Cursitor Doom wrote:

You frequently use the term "fault current" which crops up
frequently when professional electrical engineers are discussing
installations. However, for everyone else, it requires
clarification. I'm not an electrician, so I have no idea when you
use that term whether you're referring to *short circuit* current
or *earth leakage* current or something else altogether (unless you
use an example as you did above but even that's not watertight).
And then there's that lot that read this through Homeownershub -
God only knows what *they* make of it. ;-


The electrical wiring regs' meaning of 'fault' is a hard zero ohm L-N
short..

or L-E

John uses that meaning. Those of us that are more into
repairing things tend to use 'fault' to mean any failure to operate
correctly. The I with some Es seems to like to define existing terms
differently to everyone else, classic communication poor practice.

Being one who also repairs stuff, I am fully aware that the colloquial
use of "fault" is far less specific than that when used in engineering
and standards documentation for electrical systems.

No, the usage of 'fault' to mean zero ohm short only is specific to UK wiring regs not specific to engineering.

The UK wiring regs don't use "Fault" to mean zero ohm.

"Fault Current", is a specialist English and an engineering term used
by many, not only in the UK.

AIUI fault current does mean the current resulting from a zero ohm connection from live to not live.

No, you can have line to line fault currents (and line to neutral is
also "live to live" if one is being a pedant)

However if you are
going to have a meaningful discussion on fusing etc, it is quite
important that everyone uses a consistent set of terms when it matters.

Good luck with that

Make up your own terms if you like, if you think it will help.

No need. 'Fault' is in widespread use to mean any failure, including in engineering.

and "Fault Current" is not, So why use Fault if you mean Fault Current?

I'm sorry that you decided to waste everyone's time over what I thought was obvious.


NT

On Tuesday, 18 August 2020 19:19:37 UTC+1, No Name wrote:
On 18/08/2020 18:33, Scott wrote:
On Tue, 18 Aug 2020 16:30:33 +0100, No Name
wrote:

I am old enough to remember wire colours before blue for neutral, brown
for live and green/yellow for earth became commonplace...

it was red for live, black for neutral and green for earth.....

Not that long ago. The cables in my flat (not flexes) are mostly in
these colours with a warning sticker at the consumer unit saying two
colour systems are in use.



For fixed wiring in a domestic house the colours of red, green and black
last for far longer than for cables for appliances....... think the
former must have been early 2000s and the latter late 70's/early 80's?

1970


NT

On Wednesday, 19 August 2020 21:24:17 UTC+1, tony sayer wrote:
In article , John
Rumm scribeth thus
On 19/08/2020 00:19, Cursitor Doom wrote:
On Tue, 18 Aug 2020 16:42:03 +0100, charles
wrote:

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

The degaussing coils created quite a surge at switch on,

That's the kind of thing that T rated fuses are for. Fitting a regular
13A in those circumstances is just plain dumb.

BS 1362 plug fuses are in effect T rated anyway - there is no quick blow
equivalent. If your CRT switch on surge will blow a 5A fuse, what other
choice did you have (given that anything other than 3, 5, & 13A was not
readily available at the time)



Used to work years ago in a TV repair shop mainly Phillips G6, G9 and
G11 chassis sets all CRT ones never remembered having to put large fuses
in them had to wire on the mains plugs and could swear blind we only
used 5 amp ones!

They would and could blow their fuses internal ones triacs and the like
playing up..

AFAICR the degauss coils had some sort of limiter to stop a large surge
and then they had another device to get them to fade down the magnetic
field to de-mag the tube, don't ever remember them playing up either!..

2 thermistors, one NTC one PTC.


NT

On 20/08/2020 19:40:07, wrote:
On Tuesday, 18 August 2020 17:50:17 UTC+1, John Rumm wrote:
On 18/08/2020 16:03, tabbypurr wrote:
On Tuesday, 18 August 2020 15:58:52 UTC+1, John Rumm wrote:
On 18/08/2020 11:45, tabbypurr wrote:
On Tuesday, 18 August 2020 00:57:27 UTC+1, John Rumm wrote:
On 17/08/2020 23:04, tabbypurr wrote:
On Monday, 17 August 2020 22:29:49 UTC+1, Cursitor Doom wrote:

You frequently use the term "fault current" which crops up
frequently when professional electrical engineers are discussing
installations. However, for everyone else, it requires
clarification. I'm not an electrician, so I have no idea when you
use that term whether you're referring to *short circuit* current
or *earth leakage* current or something else altogether (unless you
use an example as you did above but even that's not watertight).
And then there's that lot that read this through Homeownershub -
God only knows what *they* make of it. ;-


The electrical wiring regs' meaning of 'fault' is a hard zero ohm L-N
short..

or L-E

John uses that meaning. Those of us that are more into
repairing things tend to use 'fault' to mean any failure to operate
correctly. The I with some Es seems to like to define existing terms
differently to everyone else, classic communication poor practice.

Being one who also repairs stuff, I am fully aware that the colloquial
use of "fault" is far less specific than that when used in engineering
and standards documentation for electrical systems.

No, the usage of 'fault' to mean zero ohm short only is specific to UK wiring regs not specific to engineering.

The UK wiring regs don't use "Fault" to mean zero ohm.

"Fault Current", is a specialist English and an engineering term used
by many, not only in the UK.

AIUI fault current does mean the current resulting from a zero ohm connection from live to not live.

No, you can have line to line fault currents (and line to neutral is
also "live to live" if one is being a pedant)

However if you are
going to have a meaningful discussion on fusing etc, it is quite
important that everyone uses a consistent set of terms when it matters.

Good luck with that

Make up your own terms if you like, if you think it will help.

No need. 'Fault' is in widespread use to mean any failure, including in engineering.

and "Fault Current" is not, So why use Fault if you mean Fault Current?

I'm sorry that you decided to waste everyone's time over what I thought was obvious.

I guess fault current is a well known description in current wiring
standards. So there has been no waste of time for anyone interested in
current standards and current terms.

If you're a Luddite and live in the past, then I can see your point of
view. I suppose you also think kinky means fashionable and gay means happy?

On 20/08/2020 16:46, John Rumm wrote:
On 20/08/2020 15:03, Andrew wrote:
On 18/08/2020 17:50, John Rumm wrote:
On 18/08/2020 16:03, wrote:
On Tuesday, 18 August 2020 15:58:52 UTC+1, John RummÂ* wrote:
On 18/08/2020 11:45, tabbypurr wrote:
On Tuesday, 18 August 2020 00:57:27 UTC+1, John RummÂ* wrote:
On 17/08/2020 23:04, tabbypurr wrote:
On Monday, 17 August 2020 22:29:49 UTC+1, Cursitor DoomÂ* wrote:

You frequently use the term "fault current" which crops up
frequently when professional electrical engineers are discussing
installations. However, for everyone else, it requires
clarification. I'm not an electrician, so I have no idea when you
use that term whether you're referring to *short circuit* current
or *earth leakage* current or something else altogether (unless
you
use an example as you did above but even that's not watertight).
And then there's that lot that read this through Homeownershub -
God only knows what *they* make of it. ;-


The electrical wiring regs' meaning of 'fault' is a hard zero
ohm L-N
short..

or L-E

John uses that meaning. Those of us that are more into
repairing things tend to use 'fault' to mean any failure to operate
correctly. The I with some Es seems to like to define existing
terms
differently to everyone else, classic communication poor practice.

Being one who also repairs stuff, I am fully aware that the
colloquial
use of "fault" is far less specific than that when used in
engineering
and standards documentation for electrical systems.

No, the usage of 'fault' to mean zero ohm short only is specific
to UK wiring regs not specific to engineering.

The UK wiring regs don't use "Fault" to mean zero ohm.

"Fault Current", is a specialist English and an engineering term used
by many, not only in the UK.

AIUI fault current does mean the current resulting from a zero ohm
connection from live to not live.

No, you can have line to line fault currents (and line to neutral is
also "live to live" if one is being a pedant)

However if you are
going to have a meaningful discussion on fusing etc, it is quite
important that everyone uses a consistent set of terms when it
matters.

Good luck with that

Make up your own terms if you like, if you think it will help.

No need. 'Fault' is in widespread use to mean any failure, including
in engineering.

and "Fault Current" is not, So why use Fault if you mean Fault Current?



Coows scratching on a rural wooden post carrying HV 3-phase used to be
a common live-to-live fault.

That sounds like it could be bad news for the cow!


yeah... roast beef!

John Rumm Wrote in message:
On 20/08/2020 15:03, Andrew wrote:
On 18/08/2020 17:50, John Rumm wrote:
On 18/08/2020 16:03, wrote:
On Tuesday, 18 August 2020 15:58:52 UTC+1, John Rumm wrote:
On 18/08/2020 11:45, tabbypurr wrote:
On Tuesday, 18 August 2020 00:57:27 UTC+1, John Rumm wrote:
On 17/08/2020 23:04, tabbypurr wrote:
On Monday, 17 August 2020 22:29:49 UTC+1, Cursitor Doom wrote:

You frequently use the term "fault current" which crops up
frequently when professional electrical engineers are discussing
installations. However, for everyone else, it requires
clarification. I'm not an electrician, so I have no idea when you
use that term whether you're referring to *short circuit* current
or *earth leakage* current or something else altogether (unless you
use an example as you did above but even that's not watertight).
And then there's that lot that read this through Homeownershub -
God only knows what *they* make of it. ;-


The electrical wiring regs' meaning of 'fault' is a hard zero ohm
L-N
short..

or L-E

John uses that meaning. Those of us that are more into
repairing things tend to use 'fault' to mean any failure to operate
correctly. The I with some Es seems to like to define existing terms
differently to everyone else, classic communication poor practice.

Being one who also repairs stuff, I am fully aware that the
colloquial
use of "fault" is far less specific than that when used in
engineering
and standards documentation for electrical systems.

No, the usage of 'fault' to mean zero ohm short only is specific to
UK wiring regs not specific to engineering.

The UK wiring regs don't use "Fault" to mean zero ohm.

"Fault Current", is a specialist English and an engineering term used
by many, not only in the UK.

AIUI fault current does mean the current resulting from a zero ohm
connection from live to not live.

No, you can have line to line fault currents (and line to neutral is
also "live to live" if one is being a pedant)

However if you are
going to have a meaningful discussion on fusing etc, it is quite
important that everyone uses a consistent set of terms when it
matters.

Good luck with that

Make up your own terms if you like, if you think it will help.

No need. 'Fault' is in widespread use to mean any failure, including
in engineering.

and "Fault Current" is not, So why use Fault if you mean Fault Current?



Coows scratching on a rural wooden post carrying HV 3-phase used to be
a common live-to-live fault.

That sounds like it could be bad news for the cow!

If it's any consolidation (to the cow) 1kV AC is *LOW* voltage
--

%Profound_observation%


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

On 21/08/2020 03:18, Graham. wrote:
John Rumm Wrote in message:
On 20/08/2020 15:03, Andrew wrote:
On 18/08/2020 17:50, John Rumm wrote:
On 18/08/2020 16:03, wrote:
On Tuesday, 18 August 2020 15:58:52 UTC+1, John Rumm wrote:
On 18/08/2020 11:45, tabbypurr wrote:
On Tuesday, 18 August 2020 00:57:27 UTC+1, John Rumm wrote:
On 17/08/2020 23:04, tabbypurr wrote:
On Monday, 17 August 2020 22:29:49 UTC+1, Cursitor Doom wrote:

You frequently use the term "fault current" which crops up
frequently when professional electrical engineers are discussing
installations. However, for everyone else, it requires
clarification. I'm not an electrician, so I have no idea when you
use that term whether you're referring to *short circuit* current
or *earth leakage* current or something else altogether (unless you
use an example as you did above but even that's not watertight).
And then there's that lot that read this through Homeownershub -
God only knows what *they* make of it. ;-


The electrical wiring regs' meaning of 'fault' is a hard zero ohm
L-N
short..

or L-E

John uses that meaning. Those of us that are more into
repairing things tend to use 'fault' to mean any failure to operate
correctly. The I with some Es seems to like to define existing terms
differently to everyone else, classic communication poor practice.

Being one who also repairs stuff, I am fully aware that the
colloquial
use of "fault" is far less specific than that when used in
engineering
and standards documentation for electrical systems.

No, the usage of 'fault' to mean zero ohm short only is specific to
UK wiring regs not specific to engineering.

The UK wiring regs don't use "Fault" to mean zero ohm.

"Fault Current", is a specialist English and an engineering term used
by many, not only in the UK.

AIUI fault current does mean the current resulting from a zero ohm
connection from live to not live.

No, you can have line to line fault currents (and line to neutral is
also "live to live" if one is being a pedant)

However if you are
going to have a meaningful discussion on fusing etc, it is quite
important that everyone uses a consistent set of terms when it
matters.

Good luck with that

Make up your own terms if you like, if you think it will help.

No need. 'Fault' is in widespread use to mean any failure, including
in engineering.

and "Fault Current" is not, So why use Fault if you mean Fault Current?



Coows scratching on a rural wooden post carrying HV 3-phase used to be
a common live-to-live fault.

That sounds like it could be bad news for the cow!

If it's any consolidation (to the cow) 1kV AC is *LOW* voltage

Probably not - cows (and other large quadrupeds) are particularly
sensitive to electric shock due to the ease with which they can get a
potential gradient applied across their legs.

(and the post did say HV 3-phase - so I am assuming 11kV or similar)


--
Cheers,

John.

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

In article ,
tony sayer wrote:
Used to work years ago in a TV repair shop mainly Phillips G6, G9 and
G11 chassis sets all CRT ones never remembered having to put large fuses
in them had to wire on the mains plugs and could swear blind we only
used 5 amp ones!


My 25" G6 required a 13 amp plug fuse. Smaller didn't last long. It may
have been one of the odd sizes just below 13 amp would have worked, but
life's too short to play around with such things.

--
*When the going gets tough, use duct tape

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

On Thursday, 20 August 2020 20:15:41 UTC+1, Fredxx wrote:
On 20/08/2020 19:40:07, tabbypurr wrote:
On Tuesday, 18 August 2020 17:50:17 UTC+1, John Rumm wrote:
On 18/08/2020 16:03, tabbypurr wrote:
On Tuesday, 18 August 2020 15:58:52 UTC+1, John Rumm wrote:
On 18/08/2020 11:45, tabbypurr wrote:
On Tuesday, 18 August 2020 00:57:27 UTC+1, John Rumm wrote:
On 17/08/2020 23:04, tabbypurr wrote:
On Monday, 17 August 2020 22:29:49 UTC+1, Cursitor Doom wrote:

You frequently use the term "fault current" which crops up
frequently when professional electrical engineers are discussing
installations. However, for everyone else, it requires
clarification. I'm not an electrician, so I have no idea when you
use that term whether you're referring to *short circuit* current
or *earth leakage* current or something else altogether (unless you
use an example as you did above but even that's not watertight).
And then there's that lot that read this through Homeownershub -
God only knows what *they* make of it. ;-


The electrical wiring regs' meaning of 'fault' is a hard zero ohm L-N
short..

or L-E

John uses that meaning. Those of us that are more into
repairing things tend to use 'fault' to mean any failure to operate
correctly. The I with some Es seems to like to define existing terms
differently to everyone else, classic communication poor practice.

Being one who also repairs stuff, I am fully aware that the colloquial
use of "fault" is far less specific than that when used in engineering
and standards documentation for electrical systems.

No, the usage of 'fault' to mean zero ohm short only is specific to UK wiring regs not specific to engineering.

The UK wiring regs don't use "Fault" to mean zero ohm.

"Fault Current", is a specialist English and an engineering term used
by many, not only in the UK.

AIUI fault current does mean the current resulting from a zero ohm connection from live to not live.

No, you can have line to line fault currents (and line to neutral is
also "live to live" if one is being a pedant)

However if you are
going to have a meaningful discussion on fusing etc, it is quite
important that everyone uses a consistent set of terms when it matters.

Good luck with that

Make up your own terms if you like, if you think it will help.

No need. 'Fault' is in widespread use to mean any failure, including in engineering.

and "Fault Current" is not, So why use Fault if you mean Fault Current?

I'm sorry that you decided to waste everyone's time over what I thought was obvious.

I guess fault current is a well known description in current wiring
standards.

Yep

So there has been no waste of time for anyone interested in
current standards and current terms.

there has


If you're a Luddite and live in the past, then I can see your point of
view. I suppose you also think kinky means fashionable and gay means happy?

Ah, make it up & be silly time.


NT

On Tue, 18 Aug 2020 18:37:12 +0100, Scott
wrote:

On Tue, 18 Aug 2020 15:29:33 +0100, "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
Most want something to work, before considering safety.

True, but I have never encountered an appliance not working due to
being fitted with a 1 amp or 2 amp fuse.

Not even a fan heater? ;-)

No - fan heaters are fitted with 13 amp fuses. Generally each element
is 1 Kilowatt.

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

That's because of the surge when you switch on. Same applies to
anything with a motor, such as a vacuum cleaner. You can't just go by
the rating plate.

Yeahbbut as John Rumm observed futher up the thread, the fuses under
discussion here are effectively slow-blow types anyway, so you *can*
go by the rating plate. I dunno what the (presumably substantial)
inductance of degaussing coils is, but it should provide enough to
limit the inrush current without the need for any thermistors and
whatnot. Even at 50Hz in all probability - but don't quote me on that.

On Thu, 20 Aug 2020 19:03:32 +0100, ARW
wrote:

On 18/08/2020 20:57, Scott wrote:
On Tue, 18 Aug 2020 20:30:33 +0100, ARW
wrote:

On 18/08/2020 11:51, Scott wrote:
On Tue, 18 Aug 2020 10:51:29 +0100, "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
Why do you think the system was introduced with 1, 2, 3, 5, 7, 10 and
13 amp fuses unless a lower rated fuse had safety benefits?

And it failed miserably. If a fuse blows, all the vast majority will do is
replace it to get it working again. And are very unlikely to have all
those values to hand. And the spares they are likely to find, 13 amp.

Hence the current method of having wiring capable of taking out a 13 amp
fuse if there is a sort somewhere without causing a fire. And protecting
the device itself with its own fuse if needed.

IMO changing to a 2 amp fuse can only nudge safety in one direction.

Only if it is the real thing. And even them there is very little difference.

Is the counterfeit risk inversely related to amperage then?

Depends on what it is made of?

I assumed they were the same apart from the thickness of the fuse
wire. Are you saying 2 amp fuses are more likely to be counterfeit
products than 13 amp fuses? Why would anyone counterfeit a 2 amp fuse
when they could probably sell far more 13 amp fuses?

On 21/08/2020 03:18, Graham. wrote:
John Rumm Wrote in message:
On 20/08/2020 15:03, Andrew wrote:
On 18/08/2020 17:50, John Rumm wrote:
On 18/08/2020 16:03, wrote:
On Tuesday, 18 August 2020 15:58:52 UTC+1, John Rumm wrote:
On 18/08/2020 11:45, tabbypurr wrote:
On Tuesday, 18 August 2020 00:57:27 UTC+1, John Rumm wrote:
On 17/08/2020 23:04, tabbypurr wrote:
On Monday, 17 August 2020 22:29:49 UTC+1, Cursitor Doom wrote:

You frequently use the term "fault current" which crops up
frequently when professional electrical engineers are discussing
installations. However, for everyone else, it requires
clarification. I'm not an electrician, so I have no idea when you
use that term whether you're referring to *short circuit* current
or *earth leakage* current or something else altogether (unless you
use an example as you did above but even that's not watertight).
And then there's that lot that read this through Homeownershub -
God only knows what *they* make of it. ;-


The electrical wiring regs' meaning of 'fault' is a hard zero ohm
L-N
short..

or L-E

John uses that meaning. Those of us that are more into
repairing things tend to use 'fault' to mean any failure to operate
correctly. The I with some Es seems to like to define existing terms
differently to everyone else, classic communication poor practice.

Being one who also repairs stuff, I am fully aware that the
colloquial
use of "fault" is far less specific than that when used in
engineering
and standards documentation for electrical systems.

No, the usage of 'fault' to mean zero ohm short only is specific to
UK wiring regs not specific to engineering.

The UK wiring regs don't use "Fault" to mean zero ohm.

"Fault Current", is a specialist English and an engineering term used
by many, not only in the UK.

AIUI fault current does mean the current resulting from a zero ohm
connection from live to not live.

No, you can have line to line fault currents (and line to neutral is
also "live to live" if one is being a pedant)

However if you are
going to have a meaningful discussion on fusing etc, it is quite
important that everyone uses a consistent set of terms when it
matters.

Good luck with that

Make up your own terms if you like, if you think it will help.

No need. 'Fault' is in widespread use to mean any failure, including
in engineering.

and "Fault Current" is not, So why use Fault if you mean Fault Current?



Coows scratching on a rural wooden post carrying HV 3-phase used to be
a common live-to-live fault.

That sounds like it could be bad news for the cow!

If it's any consolidation (to the cow) 1kV AC is *LOW* voltage


The cows were unharmed, but they managed to rock the pole and make the
wires swing into each other. Maybe in the 50's and 60's there was less
spacing between the phases that they have now.

On Sunday, 23 August 2020 18:25:35 UTC+1, Cursitor Doom wrote:
On Tue, 18 Aug 2020 18:37:12 +0100, Scott
wrote:
On Tue, 18 Aug 2020 15:29:33 +0100, "Dave Plowman (News)"
wrote:
In article ,
Scott wrote:

Most want something to work, before considering safety.

True, but I have never encountered an appliance not working due to
being fitted with a 1 amp or 2 amp fuse.

Not even a fan heater? ;-)

No - fan heaters are fitted with 13 amp fuses. Generally each element
is 1 Kilowatt.

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

That's because of the surge when you switch on. Same applies to
anything with a motor, such as a vacuum cleaner. You can't just go by
the rating plate.

Yeahbbut as John Rumm observed futher up the thread, the fuses under
discussion here are effectively slow-blow types anyway, so you *can*
go by the rating plate. I dunno what the (presumably substantial)
inductance of degaussing coils is, but it should provide enough to
limit the inrush current without the need for any thermistors and
whatnot. Even at 50Hz in all probability - but don't quote me on that.

Degauss coils had minimal inductance. Connect direct to mains & the only outcome is BANG


NT

On Sun, 23 Aug 2020 18:25:32 +0100, Cursitor Doom
wrote:

On Tue, 18 Aug 2020 18:37:12 +0100, Scott
wrote:

On Tue, 18 Aug 2020 15:29:33 +0100, "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
Most want something to work, before considering safety.

True, but I have never encountered an appliance not working due to
being fitted with a 1 amp or 2 amp fuse.

Not even a fan heater? ;-)

No - fan heaters are fitted with 13 amp fuses. Generally each element
is 1 Kilowatt.

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

That's because of the surge when you switch on. Same applies to
anything with a motor, such as a vacuum cleaner. You can't just go by
the rating plate.

Yeahbbut as John Rumm observed futher up the thread, the fuses under
discussion here are effectively slow-blow types anyway, so you *can*
go by the rating plate. I dunno what the (presumably substantial)
inductance of degaussing coils is, but it should provide enough to
limit the inrush current without the need for any thermistors and
whatnot. Even at 50Hz in all probability - but don't quote me on that.

Maybe it depends on one's approach to vacuuming. If you stop and
start frequently to move furniture etc, could the repeated surges
overheat the fuse?

I would tend to be less concerned about appliances that are
continuously supervised that about those left unattended.

Is the rating plate an average or maximum?

On Monday, 24 August 2020 10:02:28 UTC+1, Scott wrote:
On Sun, 23 Aug 2020 18:25:32 +0100, Cursitor Doom
wrote:

On Tue, 18 Aug 2020 18:37:12 +0100, Scott
wrote:

On Tue, 18 Aug 2020 15:29:33 +0100, "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

That's because of the surge when you switch on. Same applies to
anything with a motor, such as a vacuum cleaner. You can't just go by
the rating plate.

Yeahbbut as John Rumm observed futher up the thread, the fuses under
discussion here are effectively slow-blow types anyway, so you *can*
go by the rating plate. I dunno what the (presumably substantial)
inductance of degaussing coils is, but it should provide enough to
limit the inrush current without the need for any thermistors and
whatnot. Even at 50Hz in all probability - but don't quote me on that.

Maybe it depends on one's approach to vacuuming. If you stop and
start frequently to move furniture etc, could the repeated surges
overheat the fuse?

I don't think so. Off times give zero heat dissipation in the fuse.

I would tend to be less concerned about appliances that are
continuously supervised that about those left unattended.

Is the rating plate an average or maximum?

Maximum excluding surges.


NT

On 24/08/2020 10:02, Scott wrote:
On Sun, 23 Aug 2020 18:25:32 +0100, Cursitor Doom
wrote:

On Tue, 18 Aug 2020 18:37:12 +0100, Scott
wrote:

On Tue, 18 Aug 2020 15:29:33 +0100, "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
Most want something to work, before considering safety.

True, but I have never encountered an appliance not working due to
being fitted with a 1 amp or 2 amp fuse.

Not even a fan heater? ;-)

No - fan heaters are fitted with 13 amp fuses. Generally each element
is 1 Kilowatt.

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

That's because of the surge when you switch on. Same applies to
anything with a motor, such as a vacuum cleaner. You can't just go by
the rating plate.

Yeahbbut as John Rumm observed futher up the thread, the fuses under
discussion here are effectively slow-blow types anyway, so you *can*
go by the rating plate. I dunno what the (presumably substantial)
inductance of degaussing coils is, but it should provide enough to
limit the inrush current without the need for any thermistors and
whatnot. Even at 50Hz in all probability - but don't quote me on that.

Maybe it depends on one's approach to vacuuming. If you stop and
start frequently to move furniture etc, could the repeated surges
overheat the fuse?

I would tend to be less concerned about appliances that are
continuously supervised that about those left unattended.

Is the rating plate an average or maximum?

Maximum operating - but that does not include inrush current.


--
Cheers,

John.

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

On 23/08/2020 18:49, Scott wrote:
On Thu, 20 Aug 2020 19:03:32 +0100, ARW
wrote:

On 18/08/2020 20:57, Scott wrote:
On Tue, 18 Aug 2020 20:30:33 +0100, ARW
wrote:

On 18/08/2020 11:51, Scott wrote:
On Tue, 18 Aug 2020 10:51:29 +0100, "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
Why do you think the system was introduced with 1, 2, 3, 5, 7, 10 and
13 amp fuses unless a lower rated fuse had safety benefits?

And it failed miserably. If a fuse blows, all the vast majority will do is
replace it to get it working again. And are very unlikely to have all
those values to hand. And the spares they are likely to find, 13 amp.

Hence the current method of having wiring capable of taking out a 13 amp
fuse if there is a sort somewhere without causing a fire. And protecting
the device itself with its own fuse if needed.

IMO changing to a 2 amp fuse can only nudge safety in one direction.

Only if it is the real thing. And even them there is very little difference.

Is the counterfeit risk inversely related to amperage then?

Depends on what it is made of?

I assumed they were the same apart from the thickness of the fuse
wire. Are you saying 2 amp fuses are more likely to be counterfeit
products than 13 amp fuses? Why would anyone counterfeit a 2 amp fuse
when they could probably sell far more 13 amp fuses?

I expect the after market for 13A fuses is tiny. Typically most things
come with them fitted - so any active fuse changes will usually involve
3 or 5A.

(My stock of 13A fuses has grown with time, in spit of never having
bought any).



--
Cheers,

John.

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

On 18/08/2020 15:56, wrote:
On Tuesday, 18 August 2020 15:37:12 UTC+1, John Rumm wrote:
On 18/08/2020 11:41, tabbypurr wrote:
On Tuesday, 18 August 2020 00:33:28 UTC+1, John Rumm wrote:
On 17/08/2020 22:09, Scott wrote:
On Mon, 17 Aug 2020 21:57:17 +0100, John Rumm
wrote:
On 17/08/2020 16:59, Scott wrote:
On Mon, 17 Aug 2020 16:20:35 +0100, John Rumm
wrote:
On 17/08/2020 14:04, Cursitor Doom wrote:
On Mon, 17 Aug 2020 02:12:17 +0100, John Rumm
wrote:

Why do you think the system was introduced with 1, 2, 3,
5, 7, 10 and 13 amp fuses unless a lower rated fuse had
safety benefits?

For the limited cases where overload protection is useful.
They will all handle fault currents.

Whatever you call it, if there is only 2 amps of it instead
of 13 amps nothing will convince me that is not safer.

Define safer?


You're barking at nonexistent shadows there. Any appliance can
get a smouldering insulator fault that takes 3A but not 13A.
That's one way appliances catch fire.

And will that smouldering insulation result in an large enough rise
in current draw to blow a fuse?

Often yes, often not. Ultimately it either burns out without harm, blows a fuse or catches
fire.

Well yes, that covers most of the possibilities. Blows a fuse and
catching fire also being possible.

The problem is, its easy to generate more than enough heat to
start combustion with only a kW of power to play with, and a fuse
in a plug will happily deliver that.

Indeed. That will be solved some time in the future by electronic
load characterising fuse type circuits.

I admire your faith. To work you would need sophisticated monitoring
electronics integrated into every appliance, and they would need careful
tuning by the manufacturer to recognise what is an unusual current
profile for the appliance. Something that in many cases will not be
possible, and prohibitively expensive in cases where it is. So in the
real world economics will probably prevent that happening.

Solutions that work at the circuit level are typically very limited in
effectiveness. (see the tests on circuit level AFCIs).

For now we use fuses & mcbs
which we know only catch a percentage of such events. A 3A fuse
catches more than a 13A fuse, it blows with less energy passed.

The "energy passed" or let-though only really takes on significance when
interrupting fault currents. During normal operation, the energy
delivery from any size of fuse will deliver to all intents and purposes
unlimited power to start a fire.

I would contend that (particularly with modern appliances) plug fuses
rarely have a significant influence in reducing appliance fires in non
fault current scenarios.

If they did have significant influence, then you would expect the UK to
show a notable reduction in electrical fires compared to the rest of
Europe where plug fuses are not used, and the only protection outside of
the appliance will be the 16 or 20A MCB for the circuit.

However we have more fires per person than say France, and a similar
number compared to Germany.

(ans as you know, most electrical fires stem from misuse of appliances,
followed some long way after by faulty appliances, with faulty fixed
wiring some distance behind those)

The number of electrical fires seems to be dominated by the number of
electrical appliances in use, so wealthy nations lead the way.


IMHO Smoke alarms, RCDs etc will make a far more meaningful
contribution to safety then obsessing about fuses in the vast
majority of cases.

Indeed. Correct fusing is still wise. I don't think anyone
recommended obsession though.

You are not recommending it, but you are going on about it - endlessly.

Especially when you are not really suggesting anything substantially
different from what I said in my first post.

We just pointed out that picking an
appropriate fuse is safer..
And while true in many cases, as a blanket statement its incorrect since
there are counter examples.

In cases where its true, the amount of "safer" is very small and
difficult to qualify for *most* cases.


Trying to suggest that is obsession is
childish.

they are old enough, they may not include their own
protection, for

many modern ones don't either as your tablelamp example shows

Because it does not need it...

Generally true. Of course there are also appliances that do.

So you agree with what I say, yet still feel the need to argue?

those, yes its important they are fitted with the "right"
fuse. For

ah, we agree after all

I said that right from the outset.

others it matters less than many worry about.

[1] 100A should be a fusing time well under 0.1 secs on a 13A
fuse. So for a PVC flex we can work out the conductor size
required to cope with the I^2 . t let through energy with the
adiabatic equation:

s = sqrt( 100 ^ 2 x 0.1 ) / 115 = 0.27mm minimum CSA

(115 being the k factor for PVC insulated cable)

So even the smallest typical 0.5mm^2 CSA flex would be fine
with any fuse.

Yup. But the chinese flea bay special with copper coated steel
mains lead would catch fire.

Since it probably has the dodgy non fused plug to go with it, its a
moot point!

most don't have those. Picking a fuse to reduce fire risk is not a
moot point, it is the central point of this thread & good sensible
practice.

Its is rather missing the point. If you want to improve safety, don't
use sub standard mains leads in the first place, don't try to cure their
sins with a sprinkling of holy water after the fact.

(and many of those "fake" flexes would not take 3A sustained load
anyway)

many do, some don't

You would be a negligent to use one in the first place. How can you
seriously argue the merits of different fuse ratings when using a lead
which poses orders of magnitude more risk?

Proper flex that's partway broken also would not cope, and that
is not a rare failure mode.

Under fault conditions it may well blow at the weak part of the
flex as well. A fuse is not going to necessarily help even if it
blows at the same time. Under normal operating conditions the
appliance may stop and start or not work reliably - but again the
fuse is not going to help.

The flex may blow oc, the fuse may blow preventing a fire or the flex

Under normal operating conditions why would a fuse blow just because
there is a break in the flex? It does not blow when you turn the
appliance on and off with the switch, so why would it when you turn it
on and off with a break in the flex?

may catch fire. A fuse that lets less energy through before blow
improves the odds. I'm not sure there's much serious debate left on
that point.

Your logic is flawed[1], however I agree, no further debate is worthwhile.

[1] You are assuming it will blow.

--
Cheers,

John.

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

In article , John
Rumm scribeth thus
On 19/08/2020 21:14, tony sayer wrote:
In article , John
Rumm scribeth thus
On 19/08/2020 00:19, Cursitor Doom wrote:
On Tue, 18 Aug 2020 16:42:03 +0100, charles
wrote:

In article ,
Dave Plowman (News) wrote:
In article ,
Scott wrote:
Most want something to work, before considering safety.

True, but I have never encountered an appliance not working due to
being fitted with a 1 amp or 2 amp fuse.

Not even a fan heater? ;-)

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

The degaussing coils created quite a surge at switch on,

That's the kind of thing that T rated fuses are for. Fitting a regular
13A in those circumstances is just plain dumb.

BS 1362 plug fuses are in effect T rated anyway - there is no quick blow
equivalent. If your CRT switch on surge will blow a 5A fuse, what other
choice did you have (given that anything other than 3, 5, & 13A was not
readily available at the time)



Used to work years ago in a TV repair shop mainly Phillips G6, G9 and
G11 chassis sets all CRT ones never remembered having to put large fuses
in them had to wire on the mains plugs and could swear blind we only
used 5 amp ones!

I was making a general point, but perhaps for a TV it would in most
cases be closer to say you need 5A but looking at the ratings plate and
not understanding issues like inrush, my opt to fit 3A then have
problems with seemingly random blows.

They would and could blow their fuses internal ones triacs and the like
playing up..

AFAICR the degauss coils had some sort of limiter to stop a large surge
and then they had another device to get them to fade down the magnetic
field to de-mag the tube, don't ever remember them playing up either!..


Some seemed to just place a PTC thermistor in series with the degauss
coils such that as it heats up is reduces the current through the coils.
A fairly crude solution since it then sits there running very hot most
of the time the set is on.


Well the idea is to saturate the steel shadowmask and then let the
magnetic field die away in order to de-mag the shadowmask.

As shown here around 3 mins in!

https://www.youtube.com/watch?v=Ulaye_qVwTY


Its a wonder the whole thing worked considering the precision
manufacture of the colour TV tube shown here...


https://www.youtube.com/watch?v=0Qd4IX3wpZk
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

On Monday, 24 August 2020 23:06:44 UTC+1, John Rumm wrote:
On 18/08/2020 15:56, tabbypurr wrote:
On Tuesday, 18 August 2020 15:37:12 UTC+1, John Rumm wrote:
On 18/08/2020 11:41, tabbypurr wrote:
On Tuesday, 18 August 2020 00:33:28 UTC+1, John Rumm wrote:
On 17/08/2020 22:09, Scott wrote:
On Mon, 17 Aug 2020 21:57:17 +0100, John Rumm
wrote:
On 17/08/2020 16:59, Scott wrote:
On Mon, 17 Aug 2020 16:20:35 +0100, John Rumm
wrote:
On 17/08/2020 14:04, Cursitor Doom wrote:
On Mon, 17 Aug 2020 02:12:17 +0100, John Rumm
wrote:

Why do you think the system was introduced with 1, 2, 3,
5, 7, 10 and 13 amp fuses unless a lower rated fuse had
safety benefits?

For the limited cases where overload protection is useful.
They will all handle fault currents.

Whatever you call it, if there is only 2 amps of it instead
of 13 amps nothing will convince me that is not safer.

Define safer?


You're barking at nonexistent shadows there. Any appliance can
get a smouldering insulator fault that takes 3A but not 13A.
That's one way appliances catch fire.

And will that smouldering insulation result in an large enough rise
in current draw to blow a fuse?

Often yes, often not. Ultimately it either burns out without harm, blows a fuse or catches
fire.

Well yes, that covers most of the possibilities. Blows a fuse and
catching fire also being possible.

The problem is, its easy to generate more than enough heat to
start combustion with only a kW of power to play with, and a fuse
in a plug will happily deliver that.

Indeed. That will be solved some time in the future by electronic
load characterising fuse type circuits.

I admire your faith. To work you would need sophisticated monitoring
electronics integrated into every appliance, and they would need careful
tuning by the manufacturer to recognise what is an unusual current
profile for the appliance. Something that in many cases will not be
possible, and prohibitively expensive in cases where it is. So in the
real world economics will probably prevent that happening.

Load characterisation & electronic protection has already been done. It's too expensive for home use. But computing power is very cheap, and getting cheaper. It won't take too long before it's built into whatever the future replacement for RCBOs is. There's no requirement to put them inside appliances.


Solutions that work at the circuit level are typically very limited in
effectiveness. (see the tests on circuit level AFCIs).

of course. They do improve over time.


For now we use fuses & mcbs
which we know only catch a percentage of such events. A 3A fuse
catches more than a 13A fuse, it blows with less energy passed.

The "energy passed" or let-though only really takes on significance when
interrupting fault currents. During normal operation, the energy
delivery from any size of fuse will deliver to all intents and purposes
unlimited power to start a fire.

the reality is they frequently don't result in fire, things often burn to open circuit. So the let-through energy does matter.

I would contend that (particularly with modern appliances) plug fuses
rarely have a significant influence in reducing appliance fires in non
fault current scenarios.

History tells us otherwise. Imagine replacing them with bolts & tell us whether you're as safe.


If they did have significant influence, then you would expect the UK to
show a notable reduction in electrical fires compared to the rest of
Europe where plug fuses are not used, and the only protection outside of
the appliance will be the 16 or 20A MCB for the circuit.

which does a better job than a 13A fuse. Faster means less energy.


However we have more fires per person than say France, and a similar
number compared to Germany.

(ans as you know, most electrical fires stem from misuse of appliances,
followed some long way after by faulty appliances, with faulty fixed
wiring some distance behind those)

The number of electrical fires seems to be dominated by the number of
electrical appliances in use, so wealthy nations lead the way.


IMHO Smoke alarms, RCDs etc will make a far more meaningful
contribution to safety then obsessing about fuses in the vast
majority of cases.

Indeed. Correct fusing is still wise. I don't think anyone
recommended obsession though.

You are not recommending it, but you are going on about it - endlessly.

I'm going on about it no more than you. And it is not endless.


Especially when you are not really suggesting anything substantially
different from what I said in my first post.

someone didn't pay attention

We just pointed out that picking an
appropriate fuse is safer..

And while true in many cases, as a blanket statement its incorrect since
there are counter examples.

0.001% of counterexamples does not make it a bad idea.


In cases where its true, the amount of "safer" is very small and
difficult to qualify for *most* cases.

It is a challenge. I daresay looking into early electrical regs & insurance figures would answer that to some extent, but only as far as the the practices of the time, which were obviously a lot worse.


Trying to suggest that is obsession is
childish.

they are old enough, they may not include their own
protection, for

many modern ones don't either as your tablelamp example shows

Because it does not need it...

Generally true. Of course there are also appliances that do.

So you agree with what I say, yet still feel the need to argue?

no

those, yes its important they are fitted with the "right"
fuse. For

ah, we agree after all

I said that right from the outset.

others it matters less than many worry about.

[1] 100A should be a fusing time well under 0.1 secs on a 13A
fuse. So for a PVC flex we can work out the conductor size
required to cope with the I^2 . t let through energy with the
adiabatic equation:

s = sqrt( 100 ^ 2 x 0.1 ) / 115 = 0.27mm minimum CSA

(115 being the k factor for PVC insulated cable)

So even the smallest typical 0.5mm^2 CSA flex would be fine
with any fuse.

Yup. But the chinese flea bay special with copper coated steel
mains lead would catch fire.

Since it probably has the dodgy non fused plug to go with it, its a
moot point!

most don't have those. Picking a fuse to reduce fire risk is not a
moot point, it is the central point of this thread & good sensible
practice.

Its is rather missing the point. If you want to improve safety, don't
use sub standard mains leads in the first place,

You can tell that to end users till you're blue in the face, it's not gonna happen because most don't know and some don't care.


don't try to cure their
sins with a sprinkling of holy water after the fact.

I don't know anyone suggesting that


(and many of those "fake" flexes would not take 3A sustained load
anyway)

many do, some don't

You would be a negligent to use one in the first place.

no, just a normal member of the public that knows no different.


How can you
seriously argue the merits of different fuse ratings when using a lead
which poses orders of magnitude more risk?

that is precisely the sort of situation where good fusing practice makes most safety difference. The idea that all appliances out there in the UK are safe with a 13A fuse is simply well & truly wrong.


Proper flex that's partway broken also would not cope, and that
is not a rare failure mode.

Under fault conditions it may well blow at the weak part of the
flex as well. A fuse is not going to necessarily help even if it
blows at the same time. Under normal operating conditions the
appliance may stop and start or not work reliably - but again the
fuse is not going to help.

The flex may blow oc, the fuse may blow preventing a fire or the flex

Under normal operating conditions why would a fuse blow just because
there is a break in the flex? It does not blow when you turn the
appliance on and off with the switch, so why would it when you turn it
on and off with a break in the flex?

When flex etc shorts, either a fuse blows oc or the flex damage blows oc. Could be either.


may catch fire. A fuse that lets less energy through before blow
improves the odds. I'm not sure there's much serious debate left on
that point.

Your logic is flawed[1], however I agree, no further debate is worthwhile..

[1] You are assuming it will blow.

If you think that you really haven't followed what's being said.

The safety benefit of appropriate fusing was established a very long time ago.


NT

On 25/08/2020 00:42, tony sayer wrote:
In article , John
Rumm scribeth thus
On 19/08/2020 21:14, tony sayer wrote:
In article , John
Rumm scribeth thus
On 19/08/2020 00:19, Cursitor Doom wrote:
On Tue, 18 Aug 2020 16:42:03 +0100, charles
wrote:

In article ,
Dave Plowman (News) wrote:
In article ,
Scott wrote:
Most want something to work, before considering safety.

True, but I have never encountered an appliance not working due to
being fitted with a 1 amp or 2 amp fuse.

Not even a fan heater? ;-)

I had an early colour TV. Said 500w on the back. But needed a 13 amp
fuse...

The degaussing coils created quite a surge at switch on,

That's the kind of thing that T rated fuses are for. Fitting a regular
13A in those circumstances is just plain dumb.

BS 1362 plug fuses are in effect T rated anyway - there is no quick blow
equivalent. If your CRT switch on surge will blow a 5A fuse, what other
choice did you have (given that anything other than 3, 5, & 13A was not
readily available at the time)



Used to work years ago in a TV repair shop mainly Phillips G6, G9 and
G11 chassis sets all CRT ones never remembered having to put large fuses
in them had to wire on the mains plugs and could swear blind we only
used 5 amp ones!

I was making a general point, but perhaps for a TV it would in most
cases be closer to say you need 5A but looking at the ratings plate and
not understanding issues like inrush, my opt to fit 3A then have
problems with seemingly random blows.

They would and could blow their fuses internal ones triacs and the like
playing up..

AFAICR the degauss coils had some sort of limiter to stop a large surge
and then they had another device to get them to fade down the magnetic
field to de-mag the tube, don't ever remember them playing up either!..


Some seemed to just place a PTC thermistor in series with the degauss
coils such that as it heats up is reduces the current through the coils.
A fairly crude solution since it then sits there running very hot most
of the time the set is on.


Well the idea is to saturate the steel shadowmask and then let the
magnetic field die away in order to de-mag the shadowmask.

As shown here around 3 mins in!

https://www.youtube.com/watch?v=Ulaye_qVwTY

That sounds like a very posh Michael Aspell

2:25 - wot no mention of Wideband :-)

One tends to forget just how much on site tweaking was expected of an
installer with some early colour sets.

Its a wonder the whole thing worked considering the precision
manufacture of the colour TV tube shown here...

Yup sure, I was not suggesting it would not work - you need a decaying
magnetic field to do the degauss, and the thermistor will achieve that.

It was just the whole "leave it permanently live and in circuit" bit
that seems a bit crude... Later sets and monitors often had a relay to
switch it out when not being used.

https://www.youtube.com/watch?v=0Qd4IX3wpZk

Interesting how they etch the shadow mask, then use it to deposit the
phosphors.


--
Cheers,

John.

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

On Mon, 24 Aug 2020 22:52:32 +0100, John Rumm
wrote:

On 23/08/2020 18:49, Scott wrote:
On Thu, 20 Aug 2020 19:03:32 +0100, ARW
wrote:

On 18/08/2020 20:57, Scott wrote:
On Tue, 18 Aug 2020 20:30:33 +0100, ARW
wrote:

On 18/08/2020 11:51, Scott wrote:
On Tue, 18 Aug 2020 10:51:29 +0100, "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
Why do you think the system was introduced with 1, 2, 3, 5, 7, 10 and
13 amp fuses unless a lower rated fuse had safety benefits?

And it failed miserably. If a fuse blows, all the vast majority will do is
replace it to get it working again. And are very unlikely to have all
those values to hand. And the spares they are likely to find, 13 amp.

Hence the current method of having wiring capable of taking out a 13 amp
fuse if there is a sort somewhere without causing a fire. And protecting
the device itself with its own fuse if needed.

IMO changing to a 2 amp fuse can only nudge safety in one direction.

Only if it is the real thing. And even them there is very little difference.

Is the counterfeit risk inversely related to amperage then?

Depends on what it is made of?

I assumed they were the same apart from the thickness of the fuse
wire. Are you saying 2 amp fuses are more likely to be counterfeit
products than 13 amp fuses? Why would anyone counterfeit a 2 amp fuse
when they could probably sell far more 13 amp fuses?

I expect the after market for 13A fuses is tiny. Typically most things
come with them fitted - so any active fuse changes will usually involve
3 or 5A.

(My stock of 13A fuses has grown with time, in spit of never having
bought any).

Good point. So has mine.

On 25/08/2020 15:15, Scott wrote:
On Mon, 24 Aug 2020 22:52:32 +0100, John Rumm
wrote:

On 23/08/2020 18:49, Scott wrote:
On Thu, 20 Aug 2020 19:03:32 +0100, ARW
wrote:

On 18/08/2020 20:57, Scott wrote:
On Tue, 18 Aug 2020 20:30:33 +0100, ARW
wrote:

On 18/08/2020 11:51, Scott wrote:
On Tue, 18 Aug 2020 10:51:29 +0100, "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
Why do you think the system was introduced with 1, 2, 3, 5, 7, 10 and
13 amp fuses unless a lower rated fuse had safety benefits?

And it failed miserably. If a fuse blows, all the vast majority will do is
replace it to get it working again. And are very unlikely to have all
those values to hand. And the spares they are likely to find, 13 amp.

Hence the current method of having wiring capable of taking out a 13 amp
fuse if there is a sort somewhere without causing a fire. And protecting
the device itself with its own fuse if needed.

IMO changing to a 2 amp fuse can only nudge safety in one direction.

Only if it is the real thing. And even them there is very little difference.

Is the counterfeit risk inversely related to amperage then?

Depends on what it is made of?

I assumed they were the same apart from the thickness of the fuse
wire. Are you saying 2 amp fuses are more likely to be counterfeit
products than 13 amp fuses? Why would anyone counterfeit a 2 amp fuse
when they could probably sell far more 13 amp fuses?

I expect the after market for 13A fuses is tiny. Typically most things
come with them fitted - so any active fuse changes will usually involve
3 or 5A.

(My stock of 13A fuses has grown with time, in spit of never having
bought any).

Good point. So has mine.

Doesn't everyone save the fuse from the moulded-on plug when
disposing of yet another failed kettle/toaster/... ?

On Tuesday, 25 August 2020 19:43:46 UTC+1, Andrew wrote:
On 25/08/2020 15:15, Scott wrote:

(My stock of 13A fuses has grown with time, in spit of never having
bought any).

Good point. So has mine.

Doesn't everyone save the fuse from the moulded-on plug when
disposing of yet another failed kettle/toaster/... ?

Most people seem to throw out everything they don't need in the next 5 minutes.

On 25/08/2020 19:43, Andrew wrote:
On 25/08/2020 15:15, Scott wrote:
On Mon, 24 Aug 2020 22:52:32 +0100, John Rumm
wrote:

On 23/08/2020 18:49, Scott wrote:
On Thu, 20 Aug 2020 19:03:32 +0100, ARW
wrote:

On 18/08/2020 20:57, Scott wrote:
On Tue, 18 Aug 2020 20:30:33 +0100, ARW
wrote:

On 18/08/2020 11:51, Scott wrote:
On Tue, 18 Aug 2020 10:51:29 +0100, "Dave Plowman (News)"
wrote:

In article ,
Â*Â*Â*Â*Â* Scott wrote:
Why do you think the system was introduced with 1, 2, 3, 5, 7,
10 and
13 amp fuses unless a lower rated fuse had safety benefits?

And it failed miserably. If a fuse blows, all the vast majority
will do is
replace it to get it working again. And are very unlikely to
have all
those values to hand. And the spares they are likely to find,
13 amp.

Hence the current method of having wiring capable of taking out
a 13 amp
fuse if there is a sort somewhere without causing a fire. And
protecting
the device itself with its own fuse if needed.

IMO changing to a 2 amp fuse can only nudge safety in one
direction.

Only if it is the real thing. And even them there is very little
difference.

Is the counterfeit risk inversely related to amperage then?

Depends on what it is made of?

I assumed they were the same apart from the thickness of the fuse
wire.Â* Are you saying 2 amp fuses are more likely to be counterfeit
products than 13 amp fuses?Â* Why would anyone counterfeit a 2 amp fuse
when they could probably sell far more 13 amp fuses?

I expect the after market for 13A fuses is tiny. Typically most things
come with them fitted - so any active fuse changes will usually involve
3 or 5A.

(My stock of 13A fuses has grown with time, in spit of never having
bought any).

Good point.Â* So has mine.

Doesn't everyone save the fuse from the moulded-on plug when
disposing of yet another failed kettle/toaster/... ?

Once you have more than a lifetimes supply, not much point.




--
Cheers,

John.

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