If an appliance uses an "inherently short-circuit proof" mains transformer for its power supply, it does not need any kind of fuse - not even an over-temperature fuse inside the transformer. I have designed such products and had them successfully tested by Intertek.
John
In practice? Often mixed. In theory, you'd need to find the regs of the day. But common sense says each should have been on its own radial with the correct fuse.
Parent's house was built new in the 1930s. Originally, one 15 amp 2 pin per room, each on its own radial.
That's what I assumed as not everything needs a fuse, light bulbs tend not to have fuses. Then you have the difficulty of deciding what an appliance is. Which for most mean something in a specific range of products. The vast majority of which will end up being plugged into the mains and that item will have a 3 pin plug on the end.
I'm not sure if my hard wired cooker has any fuse(s) inside. But once when I left one ring on by mistake it some how switched it's self off after an hour or so.
Did every socket have its own connection to the fuse box or could spurs be taken off the radial circuit?
Filament lightbulbs have ballotini fuses
NT
Bulbs are rarely refered to as appliances, But as indicated the claim that 200 amps can flow doesn't really mean much, as my fuse in my CU lighting circuit is 5 amp. So what if 200 amps flows for 1 microsecond. if 200 amps can flow though my lighting circuit then 200 amps can also through through a IEC lead with a 13 amp fuse in it.
But that still misses the most important point, what is the point of the fuse ? Is it to save the bulb (perhasp referred to as the appliance) or the household wiring ?
It's to protect the wiring just like the fuse in an IEC lead. SO it's doing the same job as a fuse in a 3 pin plug. It's just been moved that's all.
Don?t you mean ?almost never have Ballotini fuses?? I?ve never seen one. Admittedly it?s a while since I?ve squinted closely at a filament bulb but I?ve just dissected one and no sign of a Ballotini fuse.
Indeed, if you?d read the link you?d posted you?d see that a) they?re expensive and b) reserved for lamps than can?t accommodate the more normal ?fuse wire? type fuse in the stem.
Ballotini Fusing This is the safest and most reliable fuse type - but also the most expensive. The fuse wire is encapsulated in a small glass tube filled with tiny glass beads called Ballotini, named after Potters Ballotini, the Italian producer. Should a secondary arc form between the broken pieces of fuse wire, its heat will melt the glass beads to form an electrically insulating barrier which contains and rapidly quenches the arc. It is so efficient that only one fuse is required, but on account of their higher price they are generally employed only in the more expensive special lamps, or decorative lamps which are too small to be able to accommodate two sufficiently long bare fuses (e.g. candle and globe lamps).
Tim
Interesting take. Designing something so it works properly in practice makes it pants?
In practice, that's exactly what happened. Mostly a 5 amp or two added to a 15 amp radial.
Never had one that bad but one day, a couple of the apprentice electricians were sent out to deliver a new colour set. They came back saying it was dead.
On investigation, I found that being mindful of the high cost of these sets they'd been ultra careful and fitted a 5A fuse - which, of course, matched the rating of the mains lead.
However, at switch on, colour sets took a mighty gulp of power to drive the degaussing coils to demagnetise the tube which considerably exceeded 5A!
The original 13A fuse was refitted and everything worked.
Thinking back to those days, I can't recall a single 13A plug anywhere being sold fitted with anything other than a 13A fuse, irrespective of what they were going to be used for, so how were the public expected to be educated to use the correct fuse for the job?
It was several years after this event that I first spotted plugs for sale with red (3A) and brown (13A) stickers and, of all places (unless I'm mistaken) it was in Woolworths!
I had similar in my latest adventures. I fitted a 1A fuse (by mistake) to a kitchen TV and it lasted a fraction of a second. I upped it to 3A and it's fine (even though the plug states 5A).
Very likely Woolworths, they stocked all sorts of handy bits and pieces.
Funnily enough, my first (temporary) job after graduating in 1990 was using AutoCad 2.6, to draw up the Woolworths packaging designs, including the diagrams and text on the back, for Volex plugs, sockets, switches and the like. It brought in some income for three months while I looked for a proper job.
SteveW
The traditional method is silver paper from a cigarette packet wrapped round the dead fuse. Perfect fit and lasts forever!
which is why 13 amp was the best fuse to use, if you wanted your 'appliance' back up and working again ASAP.
They weren't genarlly speaking but there were charts that were sold with fuse packs. Well I saw one in my fathers tobacco tin that contained spare fuses. There' weren;t as many products about then either.
I remmeber in about 1977, I was asked to check all the plugs and fuses in teh school science labs to check connections and that bthe right fuse was installed, I was provided with a list of what fuse to put in which type of product. Then the standards seemed to be 3, 5 or 13 amp, that was it.
Now it;s just a 3amp or 13amp sand no calcualting is required or should be done.
I'm not sure that of you put a 1 amp fuse in a stand with a 15W light would fail a PAT test, or any other valuse other than 3 amp but I do have a number of IEC leads with 5amp fuses that passed their PAT in 2018.
Anytime we replace such a fuse it must be with the same type IIRC and the lead must be PAT tested (with a machine) before being put in use.
As we've cherged somewhere bewteen £1.19 and £1.39 per test I tend to dump the lead by cutting off the plug and removing the fuse and it's retainer, and use a new lead. I have about 100-200 spare. Which also get tested even if they haven't been used.
Does that silver paper conduct enough ? Have to get one from a friend to try, my cat also likes that paper screwed up and plays with it more than she does actual toys I've bought.
She also like the aluminium foil rolled into a ball, not sure why but at a guess is the crincle sound and perhaps the reflections.
It certainly did in the 60s!
Favourite substitute for pop groups (usually without clearing the fault first!)
I just measure some from a packet of silk cut.
0.019 ohms between two points 1 inch apart about the lenght of a mains fuse.I didn't think this sort of silver paper conducted so much, I'll never have to buy a fuse again.
All measured at about 1 inch spacing Silver paper from a viscount chocolate bisciut 0.012 R Aluminium foil at 0.009 R a 13 amp fuse. at 0.002 R.
(Test Leads shorted together 0.0126 R )
measured using a LCR meter Agilent U1731C
Wonder how I can test the actual fusing current.
That's pretty well what I was saying. ;-)
Set in question was a G6 Philips - hybrid, using valves on the output stages. And the high inrush caused even a 13 amp fuse to fail after some time. New one gave the same sort of life.
Interesting. Never come across that. How do they work? And why fit a motor so powerful it could do an arm damage? Most are easily stopped by hand.
An arm is not a problem, a neck is. It takes very little pressure to stop either breathing or cut off blood to the brain. Children have died that way, which is why load sensors were added.
A reasonably powerful motor is required, because otherwise you could be unable to open it (or worse, close it) as the car ages and the mechanism stiffens or when there is ice on the doors. A 90's Cavalier used to have an override button on the centre console to temporarily disable the load sensors for this. These days repressing the button a few times does the same for some vehicles.
It is likely that the reason that you can easily stop a window, is because it is sensing too much load and stopping - some actually reverse a short distance as well.
SteveW
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