Fuses

I think you need closer to 4A to get out of the "forever" zone

That is true of the BS1362 fuse.

The OP has not said what type of fuses he has bought - the 6 minute maximum might suggest a glass fuse of some kind?

It is going to depend so much on the fuse holder. Try it with 4A. Only a sensitive fast blow fuse is likely to go pop with just a 50% overload.

Unless you are using it with wire that cannot carry 2A it is academic.

Our church tea ladies managed to get two 3kW kettles powered from a 4 way extender off a single 13A socket pretty regularly without ever blowing any fuses. They did once melt the extension cable though.

All the VH ones have thermal cutouts now to defend against such abuse.

what kind of fuse?

If it were a BS1362 style fuse, the looking a bit to the left of the 3A fuse curve would suggest that it might take 3A indefinitely:

When did it blow then? Brian

In the main, small current fuses often are allowed to take a surge at start up as well, at least the ones in plugs are. As long as they do not overheat and melt the plastic but blow if the device current suddenly increases in a major wee then I'm happy, otherwise you would be forever changing them, I'd imagine. Brian

It didn't, Brain. I got bored after 20 minutes and turned it off.

Yeah, here's a picture of the exact type here:

Seems there's even more leaway than I'd expected for extended over-current tolerance. Perhaps we should never fit anything bigger than a 10A fuse in a 13A plug? I think I'll toss out all my 13A fuses to be on the safe side.

Probably fake - the end caps look too shiny to be Bussman

Here are some tell tails:

(there is also more to a fuse than will it blow at an appropriate level of overload. Actually having the capacity to interrupt the flow of current, and not exploding in your face being some important ones!)

You could flip the argument, and say never fit anything other than a 13A fuse. The purpose of the fuse (for any moderately recent appliance anyway) is to provide *fault* protection to the flex - and a 13A fuse will do that just fine.

The exceptions to this are some low quality multiway extension leads where 10A would be more appropriate, or for historic appliances and flexs, or cases where a manufacturer explicitly cites a smaller fuse.

I have seen this argument so many times before and have never understood it at all. I acquired a supply of 2 amp fuses and fitted them to various low current appliances, without any difficulties. How anyone can argue that limiting the fault current is anything other than a safety enhancement confounds me.

Why do you think the system was introduced with 1, 2, 3, 5, 7, 10 and

NT

Thanks. I'm glad I am not going mad!

Whoa! Not so fast, John. I said the picture was of the exact same

The ones I have actually *look* like really nice quality. They have quite thick, substantial ceramic cases to contain any flames or hot gases. I cracked a couple open to see inside.

Not quite in this application. I'm resurrecting an old variac that needs to be brought into the 21st century. It has no fuse on the secondary side apart from a few other shortcomings safety-wise that I'm in the process of eliminating. Damn useful things to have in certain parts of the world, variacs.

was there sand?

What's not to like about that? When a 13A fuse blows, it can release a

ok.

Because you are confusing fault current with overload current. Fuses (or any other circuit protection device have *no* ability to limit fault currents. The only thing that limits a fault current the round trip impedance of the circuit with the fault. So if that is 0.23 ohms, then your fault current is 1,000 A regardless of the fuse fitted.

That will open any BS 1362 fuse pretty sharpish - the nominal current rating is not important.

What matters is that the fuse has the breaking capacity to clear the fault before something else (like the appliance flex) is destroyed / catches fire.

This is a *totally different* discussion from overload protection - foe example fitting a 13A fuse to a spur feeding multiple sockets on a ring circuit.

For the limited cases where overload protection is useful. They will all handle fault currents.

Not with a BS1362 compliant fuse - they should quench any arc and keep it contained in the fuse.

So if yours are of the "exact same type", how are they not exactly the same? :-)

Indeed, why I made the exception for historic kit where they designer may have placed the onus on the person fitting the plug to provide overload protection as well as fault protection.

(with time it became clear that joe public was not equipped to make sensible choices in this area, and the modern practice of ensuring that if overload protection was required, then it must be in the appliance itself and not on the end of the flex where it can be changed at the whim of anyone with access to a fuse (or bit of tin foil).

When the BS1362 plug system was introduced in '47 the plug fuse was normall y the appliance overload fuse, appliances mostly had little or more often n o other overload failure protection. That has changed of course, but there are still millions of appliances that have no built-in overload protection and could benefit from it safety-wise.

NT