Really? With the previous radial system, you had a fuse per socket. In theory...
So a 5 amp socket would take the fuse out if overloaded.
Your mileage appears to have varied, as they say.
The old system was even more open to abuse - using the wrong fusewire, etc.
But the idea of using lots of different fuses for plug tops is downright stupid too - unless it was impossible to fit the wrong one. Human nature being as it is.
Most want something to work, before considering safety.
On Tue, 18 Aug 2020 13:46:33 +0100, "Dave Plowman (News)" wrote: [snip]
Very true. We had a house with a fusebox with wired fuses. The electrician coiled the fusewire round three times to make sure the fuse did not blow.
A fuse blow might be a danger - depends on what its in, in what circumstance, and who will try to fix it.
That depends on what that "2A" load is - what its surge characteristics are, what inrush current it draws.
A CRT TV for example may only draw 150W when running normally, but may take quite a bit more at switch on, and when degaussing.
More to the point, is the person choosing the fuse sufficiently aware of the nature of the appliance to make a good assessment?
(I remember (a long while back) standing in the Waters & Stanton shop, when someone walks in off the street, and asks if they have 2.5A 20mm glass fuse. The young chap behind the counter says "yes, do you want quick blow or anti surge?". The customer says, "oh, I don't know, its for a portable TV, what do you think?". Sales droid thinks for a bit and says "probably quick blow". I politely butt in, and ask the customer if by any chance they have the original fuse with them? She does, so I get her to read the rating off the fuse - and as you might expect it has a T in it. So even the somewhat clued up person working in a shop stuffed full of high tech electronics and comms gear can make the wrong call)
ok I will bite...
What do you mean by substandard?
What site are we talking about? Home or work?
Few. (i.e. few will need it, and even fewer will lack it)
If you include all those babies using great grandpa's wireless huh?
Now before getting further into this, remember I have already said that there are times when using a selected and appropriate fuse *is* important, and we both understand that for the vast majority of appliances people are using today, the fuse rating will have little if any effect on safety so long as it provides adequate fault current (official meaning!) protection.
I am not suggesting that fitting a more closely tolerances fuse is necessarily wrong, only that it may introduce unintended circumstances, and it many cases will achieve no improvement in safety.
True, but I have never encountered an appliance not working due to being fitted with a 1 amp or 2 amp fuse.
What mode of action inside these appliances caused the fires? I'd wager it was in most cases insulation failure. Fuses do reduce fires resulting because they trip sooner in the process when less energy has been delivered to the flammable materials present.
rarely, though I have had one.
NT
Not even a fan heater? ;-)
I had an early colour TV. Said 500w on the back. But needed a 13 amp fuse...
not correct
if the socket was overloaded by a large margin for long enough yes. But oft en not if the appliance went into dangerous overload. Why? Sockets were in short supply and most homeowners chose plugs to fit whatever socket was the re rather than what fuse the appliance required. Those that stuck to fittin g the corect plug simply used an unfused adaptor. Result: a large percentag e of appliances were not appropriately fused.
not really
yup
Hardly. 3A fuses improve safety when used appropriately, there's no downsid e there.
'Impossible to fit the wrong one' would just recreate the inappropriate fus ing issue that existed with the round pin system.
NT
And will that smouldering insulation result in an large enough rise in current draw to blow a fuse?
(note the word "insulation" not well known for passing high currents)
See above.
The problem is, its easy to generate more than enough heat to start combustion with only a kW of power to play with, and a fuse in a plug will happily deliver that.
IMHO Smoke alarms, RCDs etc will make a far more meaningful contribution to safety then obsessing about fuses in the vast majority of cases.
Because it does not need it...
I said that right from the outset.
Since it probably has the dodgy non fused plug to go with it, its a moot point!
(and many of those "fake" flexes would not take 3A sustained load anyway)
Under fault conditions it may well blow at the weak part of the flex as well. A fuse is not going to necessarily help even if it blows at the same time. Under normal operating conditions the appliance may stop and start or not work reliably - but again the fuse is not going to help.
It isn't. If you want to propose compulsory self resetting MCBs or polyfuses etc you can, but that's a separate issue with its own tradeoffs each way.
We know people can fit the wrong fuse. So what?
Not inherently. Fuses used to come with lists of appliance types for each fuse value. Fitting a 13A in lieu of a 3 is not a problem, fitting a 3 when suitable is a small gain in fire satfey.
IME one is lucky if the person behind the counter is clued up. Glass fuses are a separate issue to what we're discussing of course.
not meeting the legal requirements
all of them!
Bzzt. Lots lack it.
are there any of those? I doubt it. But there are plenty of old heaters still in use, old lamps with undersize flex etc etc.
no, a lower fuse equals less energy delivered to the smouldering insulator before trip. Result: lower fire risk.
It always reduces fire risk. And fire is the number 1 means by which electrical failure results in injury, loss of property and death.
NT
Then correct me.
That's how my parents 1930s house was wired originally. Of course later on sockets were added to a radial.
Often yes, often not. Ultimately it either burns out without harm, blows a fuse or catches fire.
On the contrary, it's how electrical fires mostly start
Indeed. That will be solved some time in the future by electronic load char acterising fuse type circuits. For now we use fuses & mcbs which we know on ly catch a percentage of such events. A 3A fuse catches more than a 13A fus e, it blows with less energy passed.
Indeed. Correct fusing is still wise. I don't think anyone recommended obse ssion though. We just pointed out that picking an appropriate fuse is safer . Trying to suggest that is obsession is childish.
Generally true. Of course there are also appliances that do.
most don't have those. Picking a fuse to reduce fire risk is not a moot poi nt, it is the central point of this thread & good sensible practice.
many do, some don't
The flex may blow oc, the fuse may blow preventing a fire or the flex may c atch fire. A fuse that lets less energy through before blow improves the od ds. I'm not sure there's much serious debate left on that point.
NT
The UK wiring regs don't use "Fault" to mean zero ohm.
"Fault Current", is a specialist English and an engineering term used by many, not only in the UK.
Make up your own terms if you like, if you think it will help.
Around what ?. There is a slot in the fuse holder that the wire sits inside. Do you mean he coiled it round something like a pencil, or looped it back and forward again ?. This just means there is contact between the loops, surely ?.
Yes, it's what was done in the 1930s. Later it was typical to find a bunch of sockets on each fusebox fuse, and often the socket ratings did not match the fuse. So eg one might see 15A, 15A, 5A, 5A sockets on one 15A fuse.
Add the widespread use of unfused adaptors & end users' tendency to use wha tever plug fitted the available socket & the 2/5/15A fusing system routinel y descended into not being effective. This left the use of commonly 5 diffe rent mains plug types as often no more than madness.
NT
Missing or inadequate earthing probably killed more people though.
deguassing ?
AIUI fault current does mean the current resulting from a zero ohm connection from live to not live.
No need. 'Fault' is in widespread use to mean any failure, including in engineering.
NT
often not if the appliance went into dangerous overload. Why? Sockets were in short supply and most homeowners chose plugs to fit whatever socket was there rather than what fuse the appliance required. Those that stuck to fi tting the corect plug simply used an unfused adaptor. Result: a large perce ntage of appliances were not appropriately fused.
AFAIK fire has always been the main electrical killer.
NT
That fact that stuff comes with a pre-fitted plug these days, has lead to a generation that now no longer know how to fit one, and in many cases probably probably don't even know what a fuse looks like.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required