On Wednesday, 28 March 2018 15:31:19 UTC+1, wrote:
On Wednesday, 28 March 2018 14:58:30 UTC+1, whisky-dave wrote:
On Wednesday, 28 March 2018 14:25:50 UTC+1, Sam wrote:

These
sites shows you the possible pitfalls of it:

https://www.pat-testing-training.net...se-ratings.php



exactly as I said
"The purpose of the fuse within a BS1363 plug is to protect the cable."

the thinking behind the design of our household electrical system is that the plug fuse is there to protect the cable,

Well done at last.

and the appliance should either protect itself or be protected by a 13A fuse.

Yep well done again.


However IRL it does more than that for several reasons as I've already covered.

No you've not

Not that you'll listen to sense.

Show that sense then or stop talking crap.

Look back at the original question, which asked what fuse you'd use for 1115W electric fire. No mention of what lead was connected if it was a piece of 1 amp cable guess what ......


and its not illegal AFAIK to buy fuses of non standard values, I've even brought 50ma ones.

This year I've brought over 100 1 amp QB fuses and prety much every one of them has blow.

so again you don't know how to assess the correct fuse for the job.

That was the correct fuse for the job as the job was to prove to students that even a 1.5V alkaline battery can blow a fuse, its the first labsheet the students do, that's why we provided them with a glass QB fuse so they can see it blow that is the whole point.
They then check the fuse for continuity (I'd like the labsheet to get them to test this before but then I don't write labsheets academics do)

But being the type you appear to be you won't believe me.
So
http://www.engineeringbookspdf.com/m...charles-platt/

page 15 :- How to blow a fuse. fig. 1-35
They use a 3 amp automovite fuses which are far more expensive than the ones I buy. We buy ~60 of these books each year I think that is a waste of money and we should write our own labsheets for the skills course, but the academics seem to like a recommened boook.





https://www.esr.co.uk/electronics/fuses-household.htm

I also came across this from a forum:

" The problem is that of "surge" or "startup" currents. These often blow
a 3A fuse.

Yes I know and yet another reason not to use the wattage calculation on the back of pieces of equipment.

absolutely the wrong conclusion. It's just not quite as simple as 3A fuse for everything upto 699W.

Exactly so don't use caculations for this sort of thing, especailly in a test.





It;s even a bigger problem with IEC leads of which we have 100s which if just leads are treaded differntly because you have no idea what they will be connected to power wise.


This is why Table 2 of BS1363-1 effectively states that for 0.5 sq mm,
5A fuse may be used if this is a problem,

which is why most of our IEC leads have either 5 or 13 amp fueses in them.
£amp is just too low unless yuo are sure you'll never exceed 700W

I thought you said everything there had a 3 or 13A fuse.

Only if using a calculation from what's on the back of an appliance.
The majority of our leads are IEC standard with 6 amp cable as standard, on the moulded plug it says stamped/engraved on the plug 5 amp fuse fitted.
These leads aren't kettle leads you do know that don't you.

These leads are used for our soldering irons 100W our bench PSUs 300W, scopes 100W they are used with our PCs and monitors and most of the lab equipment.





As for current flow.

The appliance takes/allows the current to flow due to its
resistance/impedance and the source forces/feeds the current to the
appliance. Isn't this is what is implied by EMF of a source, ie the
Electro Motive Force?

No, emf is volts not current.

you're funny. And you seldom learn.

https://en.wikipedia.org/wiki/Electromotive_force

Electromotive force, abbreviated emf (denoted E {\displaystyle {\mathcal {E}}} {\mathcal {E}} and measured in volts),[1] is the electrical intensity or "pressure" developed by a source of electrical energy such as a battery or generator.[2] A device that converts other forms of energy into electrical energy (a "transducer") provides an emf at its output



NT