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

In article , whisky-dave writes

Yes it is, you look at the appliance rating plate and if it's in watts not amps, apply Ohm's law.

So what fuse do you put in a fan that's rated at 50W a 3 amp ? As that's what's in the fan we brought and it has been PAT tested and passed.

for me 50/230 is NOT 3 So are you saying I should put in a ~250ma fuse instead ? As that's how I'd calculate it, but I'd put a 3 amp fuse in the plug as that's what the manufactuer did.

You forgot the switch on surge. the 50w is the running power

Exactly. There's also availability, and the fact that fuses below 3A often die of their own accord over time.

NT

En el artículo , whisky-dave escribió:

Use your common sense.

BS1362 fuses are not available in 250ma, so a 3A fuse would be the best choice.

There you go then.

I can't help thinking that it would make sense for manufacturers to include "use a 3A plug fuse" on the rating plate. We see so many meaningless[1] symbols identifying all the standards it claims to follow

- why not a piece of potentially useful information?

Which would be wrong, because I as do others have to abide by the current ;=

-) legislation so calculating is less than half the battle. If I wass using cvommon sense I;'d use teh lowest fuses I have which is a 1= amp, but I use management sense which means 3 amp is chosen.

=20

yes I know and that's also why I said in another post ypou can;t use anit-s= urge=20

Yep, which is NOT arrived at through a calculation which is the point.

yep no calculation necessary=20

No I didn;t because I estimated that the switch on surge would be low for this type of applience well low is respect of the fuse rating.

How would you calculte the switch on surge if you needed to ? How would you allow for this value in the fuse you choose ?.

I wouldn't calculate it. It needs to be measured. and no, I don't have the correct meter for the job.

En el artículo , whisky-dave escribió:

If by 'management sense' you mean common sense, then we're arguing about precisely nothing :-)

below 3A often die of their own accord over time.

If you use a mA fuse that's only barely adequate for the load there's voltage drop across it.

Bill

Take the empirical approach

In message , whisky-dave writes

In message , snipped-for-privacy@care2.com writes

Fusing the neutral must be one of the most brainless ideas ever.

Yes, it ain't necessarily a good thing :-) I had a look at a couple of strings of Chrimbo lights kicking around in the basement, and they're both using 3A fuses.

Well ours all seem to be rated at 15A or 20A (with a few at 30A for things such as the cooker).

cheers

Go search youtube for "arc flash" - even 240V supplies can be quite scary.

The site as a whole is about plugs in general rather than fuses.

Fans will usually have some form of induction motor. Inrush of 5 to 9x normal operating current is not uncommon for some of these. (a small desk fan will probably be a shaded pole motor - these have less inrush IIRC)

In some cases by the type of fuse - when trying to use a fuse for close protection, you have several versions of each rating available with different time constants.

Might pee off most of the other countries in the EU though...

(Bonus!)