Are 3A plug fuses really necessary? Why not always 13A?

[John Rumm]

Induction motors in particular are well known for significant inrush. Hence why MCBs with their dual mode protection are better suited than fuses in many cases.

[John Rumm]

You said "When you have an extension lead plugged into another, or an old appliance, or something bought from China, it certainly does."

So, if you are not alluding to selecting an appropriate fuse for the extension lead, what are you suggesting?

[John Rumm]

Few people have any of them, even fewer are going to know how to select an appropriate fuse for them.

If you have some, and are aware and select the right fuse, good I am pleased for you.

For the majority of people buying and using appliances these days, they will come with a fitted plug including a 13A fuse, which will offer adequate fault protection. Chances are they will never need to replace it, and getting anal about swapping it out for a 5A fuse because its "correct" achieves nothing of value.

Agreed - no one is saying otherwise.

Now what has any of that got to do with current practice?

[Dave Plowman (News)]

That's a cable reel. The low rating is almost certainly to protect it when used not fully unwound. I'll bet the cable size is sufficient to blow a 13 amp fuse within the rated time in event of a short.

[Dave Plowman (News)]

Whether we like it or not, perhaps the majority haven't a clue about what various appliances take current wise, and care even less. So to prevent misuse and possible injury, all extension leads on sale should be capable of carrying 13 amps without melting.

[damduck-egg]

Well if you want to split hairs between lead and cable one of which happens to be wound on a reel. Perhaps the warning about unwinding fully before use they have written is unnecessary. TBH I wonder what fuse is actually fitted in the plug, enlarging the image shows the plug instruction card to show a 13 amp fuse. I reckon that is what is fitted and it relies on the inbuilt cutout it appears to have judging by the presence of the red button.

There is this

You didn't say it had to be below 13 amps, just non 13 amp.

G.Harman

[Dave Plowman (News)]

It tends to be ignored by many.

That would make more sense. Relying on a punter to replace a blown 5 amp (or whatever) plug fuse with the correct one requires the optimism of a BREXIT supporter.

Are you related to Wodney?

[PeterC]

When I wanted an extension flex (cable would be a bit awkward to handle) I was after 1.5mm. Almaost all were 1.25, so obviously 'value engineered'. I looked at the usual sources and then found that Wilko was the cheapest! Bought a reel of 50m, made up a 28m lead and still have about 18 - 20m left.

Machine Mart (sorry) did have a good one but that meant going to Leicester and by the time I could do the trip the price had gone up by a fiver.

[tabbypurr]

claim the other person said it then criticise it. And it ain't worth discus sing.

of changing extension lead fuses every time something different was plugge d in.

ie it does matter what fuse you use.

Let's get it clear in case anyone is still confused. For all plugs I pick t he lowest fuse that will reliably serve. It's what I recommend others to do too. If folk don't want to, it's not my life, it's theirs.

There are various situations in which it does make the difference, as well as many it doesn't. If you want to fail to provide very basic safety protec tion to some leads, appliances & people, again it's your life. I've already provided a list of the main situations in which it does matter. Namely old appliances noncompliant appliances extension leads A lot of these most users will never spot. They don't need to.

I have no difficulty telling what fuse is going to suit. If some users do, as some do, it really ain't my issue. All I can do is recommend best practi ce. You and others can do whatever you/they please in life.

And for the sake of clarity, I shall now state what I thought was obvious, but perhaps isn't to some. A 5A extension lead is usable for loads up to 5A continuous, and is thus best protected by a 5A fuse. You can complicate th at analysis further if you want, but I don't want.

NT

[bert]

Simples. If it's a 13 amp extension lead it gets a 13A fuse.

Don't be silly. Each plugged in appliance will have it's own appropriate fuse. The extension lead fuse simply protects the extension lead, not individual appliances/cables attached to it.

[bert]

In article , "Dave Plowman (News)" writes

How can a 13 amp fuse make it"SAFER" than a 5 amp one?

[John Rumm]

Not the fuse, the flex / appliance.

If you design your product so that it is adequately protected by a 13A fuse, then there is nothing the user can do to make it unsafe.

If you design it so that its requires lower fusing, then it means there is a danger of it having inadequate fault protection if the user fits a

13A fuse without appreciating the implications.

[Johnny B Good]

Yeah, anything less than a 13A fuse is likely to rupture with the 20+ amps degaussing surge at switch on. :-)

[John Rumm]

And how do you know what that value is? Given in many cases its not as simple as looking at the nominal run current - you may need to take into account inrush.

By basic protection do you mean fault protection? If not what else are you trying to achieve?

This seems a little contradictory - first you say it matters, and now that most users don't need to spot the cases where it matters...

Working out the optimal fusing is not a trivial exercise. Are you just providing fault protection or is overload protection also required? Can you achieve both with a single fuse? How do you reconcile potentially differing requirements for overload protection and breaking capacity?

Obvious enough - you need the fuse for fault and overload protection in that case. One of the reasons why 5A leads are far less freely available than in the past.

And yet you are suggesting complicating the analysis by selecting specific fuse sizes?

[tabbypurr]

They print the essential instructions on it and their arse is covered.

NT

[tabbypurr]

and power factor.

prevention of fire & shock. A 2A fuse can prevent that in some situations w here a 13A fails to. It will open when that chinese 0.1A mains lead is shor ted, and when the 2 slice toaster element droops so far that suddenly it's drawing too much current and about to set fire to the bread.

There's no contradiction there.

Users that don't understand it can take a simplified approach, like look at the power consumption. I also remember being given cheat sheets, these app linces want 3A, the rest 13 etc.

Those questions don't need to be answered IRL. Pick the lowest fuse that do es the job, that's it. Debating how well it protects what appliances in wha t ways doesn't achieve anything.

that doesn't complicate it beyond what I said at all. We all know there are users without any clue how to choose a fuse, that doesn't mean I'm going t o recommend they put 13A fuses in their daisy chained 5A extension leads. O r in that Chinese electrode boiler they got on Amazon, that they are not aw are of any issues with. You can if you choose, but I don't.

I'm not a full time PAT tester, but have tested enough goods to know there' s plenty of noncompliant, historic and faulty goods out there, and sub-13A extension leads aplenty. One can not realistically disregard the suitable f using of such items and expect fires, shocks & deaths to not result.

NT

[John Rumm]

More typically, they ensure it only has 6' of flex such that it stays safe on a 13A fuse.

[Dave Plowman (News)]

You'd fit a two slice toaster with a 2 amp fuse?

BTW, why are you buying Chinese products with illegal mains leads? Have you reported them?

[Dave Plowman (News)]

Think you'll find anything bought these days which conforms to EU regs will have a flex capable of blowing a 13 amp fuse in event of a short. And that's all the plug fuse is meant to do.

[tabbypurr]

No

I'm not. Any more silly qestions?

huh?

NT