Bs1362 characteristics

[flyingsparks]

Has anyone got the time graph for a bs1362 13A fuse?

 

[EFLImpudence]

Google it and go to images.

 

[JohnW2]

It's always struck me that, in some senses, and particularly for the 13A one, BS1362 fuses are functionally similar to Type B MCBs, in as much as the 'worst case' requires roughly 5 x In to ensure disconnection within 5 secs.

Kind Regards, John

 

[flyingsparks]

I don't quite get that time chart!

I need to know how long 14A would take to blow a 13A fuse but can't make sense of the time indications at the min!?

 

[JohnW2]

I don't quite get that time chart! I need to know how long 14A would take to blow a 13A fuse but can't make sense of the time indications at the min!?

I seriously doubt that it would 'ever' blow (anyone know what the I1 of a BS1362 is meant to be?). The curves are essentially vertical at 10,000 secs (167 mins, about 2.8 hours) and, even with the 'lower limit' curve that requires about 21A. I therefore doubt that a current much less than 21A would 'ever' blow the fuse.

BS1362 apparently requires that a 13A fuse should blow in no more than 400 seconds (~6.7 minutes) at 30A, but I don't know if it specifies maximum operating times for currents any lower than that. We need stillp!

Kind Regards, John

 

[ban-all-sheds]

I doubt that there's a conventional protective device of any sort made where In+1 will cause it to operate.

 

[bernardgreen]

I doubt that there's a conventional protective device of any sort made where In+1 will cause it to operate.

Conventional maybe not.....Expensive ones can be obtained and these can be accurate enough to trip at In + 5% or better. But these are not for the average domestic situation.

 

[JohnW2]

I doubt that there's a conventional protective device of any sort made where In+1 will cause it to operate.

You were not careful enough in wording that Whether or not your statement is true depends upon In being high enough! Assuming that "In+1" means "In + 1A", then even a B6 MCB should (eventually!) operate at 7A (1.17 In), and a B2 should operate in less than an hour at 3A.

However, I agree that I would not expect any conventional 13A protective device to operate at 14A (1.08 In).

Kind Regards, John

 

[JohnW2]

I doubt that there's a conventional protective device of any sort made where In+1 will cause it to operate.

Conventional maybe not.....Expensive ones can be obtained and these can be accurate enough to trip at In + 5% or better. But these are not for the average domestic situation.

One assumes that, given enough effort and expense, one can make the trip threshold as close to In (and I1) as one wishes (particularly if sensing is electronic). However, in the case of, say, standard Type B MCBs, there is actually a requirement that they should be able to carry In + 13% indefinitely without operating. I'm not sure whether that is to cater for manufacturing tolerances and in-service imprecision (i.e. so as to ensure that they never operate at In) or what.

Certainly in the case of flyingspark's question, a hypothetical B13 MCB would be required to carry 14.69A 'indefinitely' - so it certainly should not ever operate at 14A.

Kind Regards, John

 

[flyingsparks]

The reason for the question in the first place was a customer of mine is buying a 3.4kw single phase steam cleaner. He travels to people's houses and plugs it into 13a socket to use. Sometimes it could be running all day (minus half hr lunch break) I know it's not right but then what else could he do if he is going to insist on doing it? 3.4kw is 14.16A at 240v. So he probably won't get problems of blowing his plug top fuse then!

 

[ban-all-sheds]

I know it's not right but then what else could he do if he is going to insist on doing it?

Carry a fire extinguisher, a range of spare sockets, some twin and earth.

Oh - and he should check the small print of his insurance, and see if it will cover him for damage caused by negligence, and it it offers legal assistance for prosecutions for contravening the EAWR.

Seriously - the man is an idiot.

 

[JohnW2]

The reason for the question in the first place was a customer of mine is buying a 3.4kw single phase steam cleaner. He travels to people's houses and plugs it into 13a socket to use. Sometimes it could be running all day (minus half hr lunch break) I know it's not right but then what else could he do if he is going to insist on doing it? 3.4kw is 14.16A at 240v. So he probably won't get problems of blowing his plug top fuse then!

The fuse certainly won't blow, even in a whole day - as the graphs indicate, that would probably require something approaching 20A. However, it's clearly 'wrong' and the fuse might 'overheat' and damage the plug (and possibly also socket) - although with such a 'slight' overload, I doubt that, in practice, there would be a significant problem. ... but it's still wrong!

The other thing is 'time diversity', if that's the word. Presumably the element in this cleaner is thermostatically controlled, and therefore probably will not be drawing current for anything like 100% of the time it's running. If that's the case, then the current averaged over any reasonable period of time will probably be a lot less than 13A.

Kind Regards, John

 

[flyingsparks]

I agree it's a stupid idea. I was hoping to be able to show him a graph and say, yep the fuse will only last an hour and then keep blowing, etc but without such evidence to show him, all I can do is strongly discourage him...

 

[eveares]

flyingsparks; this old thread of mine may interest you. Has a bit about time and current characteristics of fuses.


//www.diynot.com/diy/threads/why-dont-lamps-come-with-a-1-amp-fuse-in-the-plugs.423162/

 

[flyingsparks]

Ok, done some research today. Karcher who make the machine, supply it with a 13A plug as standard.