The idea that the plug fuse is solely to protect the flex is a pov much pro moted, but a proper look at it shows it doesn't really add up.
Of course you can take that approach, but fitting better chosen fuses does improve safety and costs zero extra, so is the more sensible thing to do. A s the owner of many historic electrical goods & the occasional 3rd world im port I'd hate to run any of them on a 13A fuse.
As ever such ideas lead to idiocy like people being ordered to replace appr opriate fuses with higher rated ones etc.
So what, that wasn't thw question, not putting any fuse in would protect the cable even more.
What's a universal cable ?
That wasn't the question, and you don't feed the appliance, thatr's one thing our studetns get wrong too, the appliance takes current , current doesn't get pushed into thre appliance.
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.
Well if you do not have a fuse then you cut off the plug, strip the cables back (earth is optional) place the stripped back cables over the LN socket terminals (L an N reversal is not a problem) plug in the cut off plug to allow the stripped off terminals into the socket and make contact to power....
one thing our studetns get wrong too, the appliance takes current , curren t doesn't get pushed into the appliance.
re at with that.
I've not made many statements about electronics what I say is what happens in a student teaching lab. Current does NOT get pushed out of power supplies a common misunderstanding it seems when studetns go from using a 6V battery to using a PSU set to 6V they are worried it will destroy their circuits because of the higher curr ent rating, I've also had students tell me that their resistor isn't powerf ul enough.
So yuo must notice that I post evidence that I am right so far you've shown nothing regarding how to work out what fuse to put in a plug. If you had any sense yuo could find out via google.
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Quotes The fuse in a plug is a safety device designed to protect the lead rather than the appliance.
Plugs for appliances rated up to about 700 watts should have a 3-amp fuse (coloured red).
Plugs for appliances rated between about 700 watts and 3000 watts (the maximum rating of a wall socket) should be fitted with a 13-amp fuse (coloured brown).
They figures you give are suggestions/recommendations aimed at the public, there isn't anything wrong fitting a fuse of a lower rating than the cable and the 700w/3000w suggestion is only a "rule of thumb". These sites shows you the possible pitfalls of it:
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and
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Also if it were illegal to use other fuse ratings - as you imply - why is it possible to purchase fuses as shown here:
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I also came across this from a forum:
" The problem is that of "surge" or "startup" currents. These often blow a 3A fuse.
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, and 13A for 0.75 sq mm and above (with a length limit for 0.75 if it's used for certain appliance ratings)."
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?
hown nothing regarding how to work out what fuse to put in a plug.
ome/plugs-and-fuses/
er than the appliance.
se (coloured red).
maximum rating of a wall socket) should be fitted with a 13-amp fuse (colou red brown).
I;'m not the original question was and if it is part of a test for a scienc e foundation course then it should be both correct and simple.
There;s reasons when all you know is the wattgae of the electric fire witho ut knowing anything else about it.
exactly as I said "The purpose of the fuse within a BS1363 plug is to protect the cable."
NOT a good question for a science foundation course.
uses/choosing-fuses/
I've never implied that, what I have said is that you need to follow yuor e mployers recomendations and T & Cs
and from the PAT testing site, yes our PAT tester uses just 3 amp and 13 am p fuses.
QUOTE "For an appliance rated as 700W or less, a 3A fuse should be fitted. For appliances above 700W, a 13A fuse should be fitted."
So why does it say should be fitted ?
You can purchase rizzlas, too even the long ones, long spoons on chains, bo ngs, hunting knives etc...
and its not illegal AFAIK to buy fuses of non standard values, I've even br ought 50ma ones. This year I've brought over 100 1 amp QB fuses and prety much every one of them has blow.
Yes I know and yet another reason not to use the wattage calculation on the back of pieces of equipment.
It;s even a bigger problem with IEC leads of which we have 100s which if ju st leads are treaded differntly because you have no idea what they will be connected to power wise.
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
the thinking behind the design of our household electrical system is that t he plug fuse is there to protect the cable, and the appliance should either protect itself or be protected by a 13A fuse. However IRL it does more tha n that for several reasons as I've already covered. Not that you'll listen to sense.
brought 50ma ones.
f them has blow.
so again you don't know how to assess the correct fuse for the job.
he back of pieces of equipment.
absolutely the wrong conclusion. It's just not quite as simple as 3A fuse f or everything upto 699W.
just leads are treaded differntly because you have no idea what they will b e connected to power wise.
I thought you said everything there had a 3 or 13A fuse.
Look back at the original question, which asked what fuse you'd use for 111
5W electric fire. No mention of what lead was connected if it was a piece o f 1 amp cable guess what ......
n brought 50ma ones.
of them has blow.
That was the correct fuse for the job as the job was to prove to students t hat even a 1.5V alkaline battery can blow a fuse, its the first labsheet th e 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
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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 one s I buy. We buy ~60 of these books each year I think that is a waste of mon ey and we should write our own labsheets for the skills course, but the aca demics seem to like a recommened boook.
the back of pieces of equipment.
for everything upto 699W.
Exactly so don't use caculations for this sort of thing, especailly in a te st.
f just leads are treaded differntly because you have no idea what they will be connected to power wise.
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 > > As for current flow.
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Electromotive force, abbreviated emf (denoted E {\displaystyle {\mathcal {E }}} {\mathcal {E}} and measured in volts),[1] is the electrical intensity o r "pressure" developed by a source of electrical energy such as a battery o r generator.[2] A device that converts other forms of energy into electrica l energy (a "transducer") provides an emf at its output
f just leads are treaded differntly because you have no idea what they will be connected to power wise.
I'm not, I haven't any 10amp IEC cables. I mhave IEC cables that have cable rating of 6 amps and 5 amp fuses.
With equipement which have dedicated leads attached that can't be removed t hey have whatever fuses they have come with the appliance lead, if the fuse blows then the same value fuse is replaced and the item is stored until it gets tested by our PAT taster, it doesn't get put back into use until they have tested it.
Very few items in the lab have dedicated leads just angle poised lamps and the 2KW radiators, which have 13amp fuses NOT 8.7 amp which I assume you'd use, but no they have 13amp for some reason.
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31036 The IET sponsers some of our projects here, they send us goodie bags to for teh students who get a free membership, so we do and should follow their g iudance where possible.
QUOTE This has been a source of confusion for many years.
The IEC socket is rated at 10A, but most IEC leads supplied with equipment are fitted with 0.75mm cable, which is (nominally)rated at 6A. Hence, you w ould expect to see a 5A fuse, and this is what is normally fitted.
However, BS1362 only now recognises 2 values of plug top fuse, stating that a 3A fuse should be fitted to an appliance of less than 700W and a 13A fus e to an appliance bigger.
Consequently, it is not uncommon to find brand new IEC cables fitted with 1
3A fuses.
Now go argue with the institute of electrical engineers about it.
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