Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v
1150/240=4.79 so theoretically a 5A fuse shoud do.
--

Graham.
%Profound_observation%

Unless there is a surge on start up which can happen on heaters.
I'm very surprised we do not get 7.5 amp fuses for this sort of thing. 13
amp ones go with a heck of a bang. You can get very slow blow fuses of
course with a lot of that heat conducting stuff in them, but I'd guess a
lot of fuses one sees in pound shops are dodgy in the extreme.
Brian

--
----- -
This newsgroup posting comes to you directly from...
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"Graham." wrote in message
...

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire
at a potential difference of 240v
1150/240=4.79 so theoretically a 5A fuse shoud do.
--

Graham.
%Profound_observation%

On Tuesday, March 20, 2018 at 2:48:07 AM UTC+11, Graham. wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v
1150/240=4.79 so theoretically a 5A fuse shoud do.
--

Graham.
%Profound_observation%

May be 5A will do, as "cold" heater element resistance would be higher than normal heating.

On Thu, 22 Mar 2018 18:50:17 -0700, gopalansampath wrote:

On Tuesday, March 20, 2018 at 2:48:07 AM UTC+11, Graham. wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v
1150/240=4.79 so theoretically a 5A fuse shoud do.
--

Graham.
%Profound_observation%

May be 5A will do, as "cold" heater element resistance would be higher
than normal heating.

Surely it's the other way round.

--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

On 23 Mar 2018 09:55:54 GMT, Bob Eager wrote:

On Thu, 22 Mar 2018 18:50:17 -0700, gopalansampath wrote:

On Tuesday, March 20, 2018 at 2:48:07 AM UTC+11, Graham. wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v
1150/240=4.79 so theoretically a 5A fuse shoud do.
--

Graham.
%Profound_observation%

May be 5A will do, as "cold" heater element resistance would be higher
than normal heating.

Surely it's the other way round.

AIUI the type of heater that is in an incandescent lamp - filament, of
course - has low initial resistance so that it comes on 'instantaneously'
whereas an electric fire/kettle/shower is pretty well constant.
Cold inrush to a 3kW kettle+bad idea.
The 2 elements in my electric shower, measured when cold of course, have the
resistance corellating to the rated power.
The electric kettle stays the same, although the meter won't show the power
for the first cycle or two.
--
Peter.
The gods will stay away
whilst religions hold sway

On Friday, March 23, 2018 at 8:55:58 PM UTC+11, Bob Eager wrote:
On Thu, 22 Mar 2018 18:50:17 -0700, gopalansampath wrote:

On Tuesday, March 20, 2018 at 2:48:07 AM UTC+11, Graham. wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v
1150/240=4.79 so theoretically a 5A fuse shoud do.
--

Graham.
%Profound_observation%

May be 5A will do, as "cold" heater element resistance would be higher
than normal heating.

Surely it's the other way round.

--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

OOps! I stand corrected. Surely fuse rating shall be higher than % Amps.

On Friday, 23 March 2018 01:50:20 UTC, wrote:
On Tuesday, March 20, 2018 at 2:48:07 AM UTC+11, Graham. wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v
1150/240=4.79 so theoretically a 5A fuse shoud do.
--

Graham.
%Profound_observation%

May be 5A will do, as "cold" heater element resistance would be higher than normal heating.

But according to regulations in the UK on changing fuses it should be either a 3A for below 720W or a 13amp for above 720W .

https://www.rospa.com/home-safety/uk...hoosing-fuses/

whisky-dave wrote:

But according to regulations in the UK on changing fuses it should be either a 3A for below 720W or a 13amp for above 720W .

https://www.rospa.com/home-safety/uk...hoosing-fuses/

ROSPA doesn't represent "regulations", it's just advice, based on the
ratings of fuses they expect people to have at hand, and even that page
suggests 5A for some appliances ...

On Friday, 23 March 2018 13:37:35 UTC, Andy Burns wrote:
whisky-dave wrote:

But according to regulations in the UK on changing fuses it should be either a 3A for below 720W or a 13amp for above 720W .

https://www.rospa.com/home-safety/uk...hoosing-fuses/

ROSPA doesn't represent "regulations", it's just advice, based on the
ratings of fuses they expect people to have at hand, and even that page
suggests 5A for some appliances ...

As I said it's a bad question and in this university we have the regulations which tell us we must only use 3 & 13amp fuses, about 10 years ago I and others had the job of checking all fuses and replacving them with the 'correct ones'
i.e 3 or 5, this is one reason why I have dozens of 5, 7 and 10 amp fuses, I even have 1 amp and 2 amp that I used in angle poised lamps with 40 or 60w bulbs.
ANd don;t forget the FUSE is to protect the cable NOT the item of equipent so it really doesnlt matter what current rating the electric fire is, you put the fuse in that is correct for the cable.

On Friday, 23 March 2018 13:05:57 UTC, whisky-dave wrote:
On Friday, 23 March 2018 01:50:20 UTC, wrote:
On Tuesday, March 20, 2018 at 2:48:07 AM UTC+11, Graham. wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v
1150/240=4.79 so theoretically a 5A fuse shoud do.
--

Graham.
%Profound_observation%

May be 5A will do, as "cold" heater element resistance would be higher than normal heating.

But according to regulations in the UK on changing fuses it should be either a 3A for below 720W or a 13amp for above 720W .

incorrect.

https://www.rospa.com/home-safety/uk...hoosing-fuses/

ROSPA is not regulations.

On Saturday, 24 March 2018 03:16:00 UTC, wrote:
On Friday, 23 March 2018 13:05:57 UTC, whisky-dave wrote:
On Friday, 23 March 2018 01:50:20 UTC, wrote:
On Tuesday, March 20, 2018 at 2:48:07 AM UTC+11, Graham. wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v
1150/240=4.79 so theoretically a 5A fuse shoud do.
--

Graham.
%Profound_observation%

May be 5A will do, as "cold" heater element resistance would be higher than normal heating.

But according to regulations in the UK on changing fuses it should be either a 3A for below 720W or a 13amp for above 720W .

incorrect.

https://www.rospa.com/home-safety/uk...hoosing-fuses/

ROSPA is not regulations.

Those are the one we have to follow they are part of college regualtions that all plugs were to be fitted with either a 3amp or 13amp fuse NOTHING else was to be used for stabndard lab equipment.

On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave
wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v

Assuming you mean at the BS1363 plug then the fuse should be sized to protect
the cable.
--

On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote:
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave
wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v

Assuming you mean at the BS1363 plug then the fuse should be sized to protect
the cable.
--

Nice, that's the sort of answer I'd expect :-)

But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look).

I have also been told that H&S state that consumers/users should only use either a 3A of 13 amp fuse in a plug and that is what we as technicians have been told to use, even though I have loads of fuses including 1A, 2A, 5A, 7A, 10A and 13A


https://www.rospa.com/home-safety/uk...hoosing-fuses/

On 19/03/2018 16:18, whisky-dave wrote:
On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote:
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave
wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v

Assuming you mean at the BS1363 plug then the fuse should be sized to protect
the cable.
--

Nice, that's the sort of answer I'd expect :-)

But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look).

I have also been told that H&S state that consumers/users should only use either a 3A of 13 amp fuse in a plug and that is what we as technicians have been told to use, even though I have loads of fuses including 1A, 2A, 5A, 7A, 10A and 13A


https://www.rospa.com/home-safety/uk...hoosing-fuses/



I think some of that might be down to BS7671 only mentioning 3A and 13A
fuses. Although I cannot find a reference to that ATM.

--
Adam

On Monday, 19 March 2018 16:18:39 UTC, whisky-dave wrote:
On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote:
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave
wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v

Assuming you mean at the BS1363 plug then the fuse should be sized to protect
the cable.
--

Nice, that's the sort of answer I'd expect :-)

But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look).

5A is a better answer than 13. It would give added protection against a partial short of the heating element. Either is compliant with BS. TBH this is very basic stuff.

I have also been told that H&S state that consumers/users should only use either a 3A of 13 amp fuse in a plug and that is what we as technicians have been told to use, even though I have loads of fuses including 1A, 2A, 5A, 7A, 10A and 13A

complete cobblers of course.

https://www.rospa.com/home-safety/uk...hoosing-fuses/

a useful rule of thumb for folks that need to be told which fuse because they have no idea. Such people normally only have 3 & 13A. That's all it is.


NT

wrote:

On Monday, 19 March 2018 16:18:39 UTC, whisky-dave wrote:
On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote:
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave
wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

Assuming you mean at the BS1363 plug then the fuse should be sized to
protect
the cable.
--

Nice, that's the sort of answer I'd expect :-)

But this was a question given to students doing our science foundation
course where they are expected to say 5 Amps. (a student has left their
marked paper (mid semester test) in the lab so I thought I'd have a
look).

5A is a better answer than 13. It would give added protection against a
partial short of the heating element. Either is compliant with BS. TBH
this is very basic stuff.

It depends on the heating elements temperature coefficient of
resistivity and how hot it gets. Some 1.15kW heaters may draw much
more than 5A for tens of seconds on starting.



I have also been told that H&S state that consumers/users should only
use either a 3A of 13 amp fuse in a plug and that is what we as
technicians have been told to use, even though I have loads of fuses
including 1A, 2A, 5A, 7A, 10A and 13A

complete cobblers of course.


https://www.rospa.com/home-safety/uk...icity/plugs-fu
ses/choosing-fuses/

a useful rule of thumb for folks that need to be told which fuse because
they have no idea. Such people normally only have 3 & 13A. That's all it
is.


NT


--

Roger Hayter

On Monday, 19 March 2018 19:39:09 UTC, Roger Hayter wrote:
tabbypurr wrote:
On Monday, 19 March 2018 16:18:39 UTC, whisky-dave wrote:
On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote:
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave
wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

Assuming you mean at the BS1363 plug then the fuse should be sized to
protect
the cable.
--

Nice, that's the sort of answer I'd expect :-)

But this was a question given to students doing our science foundation
course where they are expected to say 5 Amps. (a student has left their
marked paper (mid semester test) in the lab so I thought I'd have a
look).

5A is a better answer than 13. It would give added protection against a
partial short of the heating element. Either is compliant with BS. TBH
this is very basic stuff.

It depends on the heating elements temperature coefficient of
resistivity and how hot it gets. Some 1.15kW heaters may draw much
more than 5A for tens of seconds on starting.

a) which ones?
b) fuses are pretty tolerant of that. Look up the curves.


NT

On 19/03/2018 19:28, wrote:
On Monday, 19 March 2018 16:18:39 UTC, whisky-dave wrote:
On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote:
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave
wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v

Assuming you mean at the BS1363 plug then the fuse should be sized to protect
the cable.
--

Nice, that's the sort of answer I'd expect :-)



Does the BS require that the heating element should burn out before the
cable does (say there's a voltage surge)?

And does the BS require that the element will burn out safely without
setting fire to something?

On 19/03/2018 19:48, GB wrote:
On 19/03/2018 19:28, wrote:
On Monday, 19 March 2018 16:18:39 UTC, whisky-daveÂ* wrote:
On Monday, 19 March 2018 16:11:42 UTC, The Other MikeÂ* wrote:
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave

wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW
electric fire at a potential difference of 240v

Assuming you mean at the BS1363 plug then the fuse should be sized
to protect
the cable.
--

Nice, that's the sort of answer I'd expect :-)



Does the BS require that the heating element should burn out before the
cable does (say there's a voltage surge)?

And does the BS require that the element will burn out safely without
setting fire to something?


I don't think that BS761 has an opinion on it. Overload is not relevant
(the load is set by the heaters wattage) so in this case only fault
current applies.

If you have such a voltage surge then the least of your worries would be
a 1.15kW heater!

--
Adam

In article ,
writes:
On Monday, 19 March 2018 16:18:39 UTC, whisky-dave wrote:
On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote:
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave
wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v

Assuming you mean at the BS1363 plug then the fuse should be sized to protect
the cable.

Nice, that's the sort of answer I'd expect :-)

But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look).

5A is a better answer than 13. It would give added protection against a partial short of the heating element. Either is compliant with BS. TBH this is very basic stuff.

A 5A fuse passing 4A will give off 0.64W, generating some heating
and deterioration of the plug over time.

A 13A fuse passing 4A will give off 0.09W, resulting in less heating
in the plug and longer life.

Unless the heater has a longer flex than is allowed by EU regulations
(which requires the flex is protected against fault current when fused
at 16A), a 13A fuse will protect the cable OK.

(A BS1362 fuse gives off about 1W at full load current.)

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

On Monday, 19 March 2018 19:28:09 UTC, wrote:
On Monday, 19 March 2018 16:18:39 UTC, whisky-dave wrote:
On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote:
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave
wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v

Assuming you mean at the BS1363 plug then the fuse should be sized to protect
the cable.
--

Nice, that's the sort of answer I'd expect :-)

But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look).

5A is a better answer than 13. It would give added protection against a partial short of the heating element. Either is compliant with BS. TBH this is very basic stuff.

Which is why it's a question in the science foundation course I supose.


I have also been told that H&S state that consumers/users should only use either a 3A of 13 amp fuse in a plug and that is what we as technicians have been told to use, even though I have loads of fuses including 1A, 2A, 5A, 7A, 10A and 13A

complete cobblers of course.

https://www.rospa.com/home-safety/uk...hoosing-fuses/

a useful rule of thumb for folks that need to be told which fuse because they have no idea. Such people normally only have 3 & 13A. That's all it is.

The same fuses our PAT tester person uses then.

So it really depends on your job then and little to do with the applienace ?
So as I would think not a very good quetion to ask.

whisky-dave pretended :
Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at
a potential difference of 240v

5amp ought to cover it, but it is very tight. If it fails find a 10amp.

On 19/03/2018 16:15, Harry Bloomfield wrote:
whisky-dave pretended :
Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

5amp ought to cover it, but it is very tight. If it fails find a 10amp.

It isn't *all* that tight in practice but the plug will run slightly
warm. A nominal 5A fuse will take nearly 20A to blow in the first second
and will probably support a current of 7A almost indefinitely. eg.

https://docs-emea.rs-online.com/webd...6b8002b71e.pdf

It would be much more challenging with a halogen light where there is a
significant inrush current when the filament is cold. An electric fire
is a relatively benign load with a decently high cold resistance.

Nominally 13A fuses will support boiling two 3kW kettles for long enough
to destroy the still coiled up extension cable they were plugged into.

All our village hall extension cables now have thermal overload
protection to save them from the church's tea ladies.

--
Regards,
Martin Brown

In message
Martin Brown wrote:

On 19/03/2018 16:15, Harry Bloomfield wrote:
whisky-dave pretended :
Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

5amp ought to cover it, but it is very tight. If it fails find a 10amp.

It isn't *all* that tight in practice but the plug will run slightly
warm. A nominal 5A fuse will take nearly 20A to blow in the first second
and will probably support a current of 7A almost indefinitely. eg.

https://docs-emea.rs-online.com/webd...6b8002b71e.pdf

It would be much more challenging with a halogen light where there is a
significant inrush current when the filament is cold. An electric fire
is a relatively benign load with a decently high cold resistance.

Nominally 13A fuses will support boiling two 3kW kettles for long enough
to destroy the still coiled up extension cable they were plugged into.

This is due to induction heating not resistive heating by the load
supplied.

All our village hall extension cables now have thermal overload
protection to save them from the church's tea ladies.



--
John Bryan

On Monday, 19 March 2018 19:25:17 UTC, John Bryan wrote:
In message
Martin Brown wrote:
On 19/03/2018 16:15, Harry Bloomfield wrote:
whisky-dave pretended :

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

5amp ought to cover it, but it is very tight. If it fails find a 10amp.

It isn't *all* that tight in practice but the plug will run slightly
warm. A nominal 5A fuse will take nearly 20A to blow in the first second
and will probably support a current of 7A almost indefinitely. eg.

https://docs-emea.rs-online.com/webd...6b8002b71e.pdf

It would be much more challenging with a halogen light where there is a
significant inrush current when the filament is cold. An electric fire
is a relatively benign load with a decently high cold resistance.

Nominally 13A fuses will support boiling two 3kW kettles for long enough
to destroy the still coiled up extension cable they were plugged into.

This is due to induction heating not resistive heating by the load
supplied.

Since current is the same but opposite direction in L&N conductors there is no significant induction heating.


NT

John Bryan wrote:

In message
Martin Brown wrote:

On 19/03/2018 16:15, Harry Bloomfield wrote:
whisky-dave pretended :
Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

5amp ought to cover it, but it is very tight. If it fails find a 10amp.

It isn't *all* that tight in practice but the plug will run slightly
warm. A nominal 5A fuse will take nearly 20A to blow in the first second
and will probably support a current of 7A almost indefinitely. eg.

https://docs-emea.rs-online.com/webd...6b8002b71e.pdf

It would be much more challenging with a halogen light where there is a
significant inrush current when the filament is cold. An electric fire
is a relatively benign load with a decently high cold resistance.

Nominally 13A fuses will support boiling two 3kW kettles for long enough
to destroy the still coiled up extension cable they were plugged into.

This is due to induction heating not resistive heating by the load
supplied.

No it is due to resistive heating and poor heat dissipation by the
coiled lead.



All our village hall extension cables now have thermal overload
protection to save them from the church's tea ladies.


--

Roger Hayter

on 19/03/2018, John Bryan supposed :
This is due to induction heating not resistive heating by the load
supplied.

Rubbish, there will be no inductive heating effect. The current in live
will match that in neutral and thus negate any induction. The only
heating effect in a coiled lead on ac is that of resistive heating,
which becomes a problem on a coiled up lead, because the heat produced
is unable to escape.

On 19/03/2018 19:55, Harry Bloomfield wrote:
on 19/03/2018, John Bryan supposed :
This is due to induction heating not resistive heating by the load
supplied.

Rubbish, there will be no inductive heating effect. The current in live
will match that in neutral and thus negate any induction. The only
heating effect in a coiled lead on ac is that of resistive heating,
which becomes a problem on a coiled up lead, because the heat produced
is unable to escape.

Could not have put it better!

On Mon, 19 Mar 2018 19:55:23 +0000, Harry Bloomfield wrote:

on 19/03/2018, John Bryan supposed :
This is due to induction heating not resistive heating by the load
supplied.

Rubbish, there will be no inductive heating effect. The current in live
will match that in neutral and thus negate any induction. The only
heating effect in a coiled lead on ac is that of resistive heating,
which becomes a problem on a coiled up lead, because the heat produced
is unable to escape.

+1

Nicely put. That saved me having to stick *my* oar in. :-)

--
Johnny B Good

John Bryan wrote:
All our village hall extension cables now have thermal overload
protection to save them from the church's tea ladies.

Hmm, a strict reading of the rules would suggest that your electrical
installation is defective - not fit for purpose as you should have
sockets available where the kettles need to go, rather than using
extension leads. Of course, how to provide sockets in the middle of the
floor for kettles which don't then become a trip hazard when the same
area is used as a dance floor is an interesting challenge...


Mike

On 19/03/2018 21:34, Mike Humphrey wrote:
John Bryan wrote:
All our village hall extension cables now have thermal overload
protection to save them from the church's tea ladies.

Hmm, a strict reading of the rules would suggest that your electrical
installation is defective - not fit for purpose as you should have
sockets available where the kettles need to go, rather than using

There is power where the kettles should go, but the tea ladies sometimes
do strange things to avoid walking about 3m to the kitchen bench. The
extension was coiled up and being used essentially as a 2 way adaptor so
they could plug in multiple kettles at once on a nearby table instead.

extension leads. Of course, how to provide sockets in the middle of the
floor for kettles which don't then become a trip hazard when the same
area is used as a dance floor is an interesting challenge...

I have concluded that you have to assume that people will do crazy
things and defend against them. Rules only go so far and get ignored.

--
Regards,
Martin Brown

In article ,
whisky-dave wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

If you're talking a plug fuse, the load is irrelevant. As it is to protect
the flex etc. In other words, a table light with a 20 watt bulb would be
fine with a 13 amp fuse if the cable was rated at 13 amps.

--
*The closest I ever got to a 4.0 in school was my blood alcohol content*

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

On 19/03/2018 16:53, Dave Plowman (News) wrote:
In article ,
whisky-dave wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

If you're talking a plug fuse, the load is irrelevant. As it is to protect
the flex etc. In other words, a table light with a 20 watt bulb would be
fine with a 13 amp fuse if the cable was rated at 13 amps.


Won't all fuses less than 13a protect the cable then!

On Monday, 19 March 2018 17:59:10 UTC, Sam wrote:
On 19/03/2018 16:53, Dave Plowman (News) wrote:
In article ,
whisky-dave wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

If you're talking a plug fuse, the load is irrelevant. As it is to protect
the flex etc. In other words, a table light with a 20 watt bulb would be
fine with a 13 amp fuse if the cable was rated at 13 amps.


Won't all fuses less than 13a protect the cable then!

No, for 4 reasons.

1. Some appliances have old thin cables that come nowhere near being protected by a 10A fuse.
2. Some old appliances need low current mains fuses to give them basic safety protection.
3. Some new appliances have noncompliant CCS cables.
3. Some 13A fuses are in reality 13A or greater. This applies both to old pre-ASTM and new counterfeit fuses.


NT

On Mon, 19 Mar 2018 12:31:42 -0700 (PDT), wrote:

On Monday, 19 March 2018 17:59:10 UTC, Sam wrote:
On 19/03/2018 16:53, Dave Plowman (News) wrote:
In article ,
whisky-dave wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

If you're talking a plug fuse, the load is irrelevant. As it is to protect
the flex etc. In other words, a table light with a 20 watt bulb would be
fine with a 13 amp fuse if the cable was rated at 13 amps.


Won't all fuses less than 13a protect the cable then!

No, for 4 reasons.

1. Some appliances have old thin cables that come nowhere near being protected by a 10A fuse.
2. Some old appliances need low current mains fuses to give them basic safety protection.
3. Some new appliances have noncompliant CCS cables.
3. Some 13A fuses are in reality 13A or greater. This applies both to old pre-ASTM and new counterfeit fuses.

NT

With the v. few items with old, thin flex I have fuses of 1, 2, 3, 5, 7, 10
& 13A semi-sorted in 3 boxen. I suppose, with a bit of modding, I could also
look at sub-1A fuses (fast, delay, slow), but nowadays they're pretty well
redundant.
We had an oven at work that drew about 15 - 16A peak but with odd solenoids
banging in at times. The v. old 13A fuse went and the replacements would
last only days - not good in military testing.
Had to hard-wire it to a 20A fused breaker in the end.
--
Peter.
The gods will stay away
whilst religions hold sway

On Mon, 19 Mar 2018 17:59:03 +0000, Sam wrote:

On 19/03/2018 16:53, Dave Plowman (News) wrote:
In article ,
whisky-dave wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

If you're talking a plug fuse, the load is irrelevant. As it is to
protect the flex etc. In other words, a table light with a 20 watt bulb
would be fine with a 13 amp fuse if the cable was rated at 13 amps.


Won't all fuses less than 13a protect the cable then!

Yes. Provided the load doesn't demand the use of a higher fuse rating,
the lower the better the protection. The only issue would that of the
heating effect inside the plug when running close to the chosen fuse
rating current limit[1]. With a table lamp, even a 1A fuse will be safe
from this unless you fit a 250W GLS lamp (in which case, choose a 2 or 3
amp fuse. :-).

[1] All fuses rely upon the heating effect to perform their function so
the plug's fuse holder must be designed to cope with the circa 1 to 2
watt's worth of dissipation whenever the fuse is carrying its rated
current. The lower the fuse rating, the lower the dissipation at the
rated current. However, this isn't a linear variation since the thicker
fuse wire inside a 13A fuse cartridge will conduct the heat away more
rapidly via its end caps into the Live pin and the live wire termination
than the thinner wire in a 1A fuse cartridge.

--
Johnny B Good

On Monday, 19 March 2018 17:02:42 UTC, Dave Plowman (News) wrote:
In article ,
whisky-dave wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

If you're talking a plug fuse, the load is irrelevant. As it is to protect
the flex etc. In other words, a table light with a 20 watt bulb would be
fine with a 13 amp fuse if the cable was rated at 13 amps.

But that wasn't the question was it.
This was a mid-term test, so you would got this question wrong.

On Monday, 19 March 2018 17:02:42 UTC, Dave Plowman (News) wrote:
In article ,
whisky-dave wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

If you're talking a plug fuse, the load is irrelevant. As it is to protect
the flex etc. In other words, a table light with a 20 watt bulb would be
fine with a 13 amp fuse if the cable was rated at 13 amps.

But that wasn't the question was it.
This was a mid-term test, so you would got this question wrong.


Often with examination question, the right answer is the one the
examiner is expecting. I have had that dilema many times.

I hand my grandson a sheet of A4 paper and ask him what shape it is,
he replies it's a rectangle. Wrong.
--

Graham.
%Profound_observation%

On 20/03/2018 19:15, Graham. wrote:
On Monday, 19 March 2018 17:02:42 UTC, Dave Plowman (News) wrote:
In article ,
whisky-dave wrote:

Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric
fire at a potential difference of 240v

If you're talking a plug fuse, the load is irrelevant. As it is to protect
the flex etc. In other words, a table light with a 20 watt bulb would be
fine with a 13 amp fuse if the cable was rated at 13 amps.

But that wasn't the question was it.
This was a mid-term test, so you would got this question wrong.


Often with examination question, the right answer is the one the
examiner is expecting. I have had that dilema many times.

I hand my grandson a sheet of A4 paper and ask him what shape it is,
he replies it's a rectangle. Wrong.

What is it, a parallelogram? A trapezium? A quadrilateral perhaps.

--
Max Demian