John. You are back on form doing really useful, informative videos on subjects many take for granted. Please keep these coming. I'm still waiting for the one on over/undertightening copper conductors with brass screws, potential fatigue stress in copper wire if one works in the same patress box repeatedly, wires coming loose in hidden junction boxes, etc, etc.
I'd also like to see some tests done to figure out if plastic junction boxes are as safe as metal ones (that of which are properly grounded of course).
In the case of the 30 amp fuse replaced with a 40 amp breaker, I certainly hope the wiring was verified to be rated for that amount of current, or replaced with appropriate wiring.
Keep in mind that if you have multiple cables bundled together, you have to derate them otherwise they pose a fire hazard because the heat can build up in the bundle. (Think of it like a wound up extension cord/lead.)
I had a similar thing when someone fitted a 10.5kw shower on a 30amp rewireable fuse holder and it started to smell of burning fish... I think it was on 6mm cable as well... not a good situation... I told him to get the plumber back who fitted it and fit the correct shower again..
in a fast overload, sure wont be a problem however what with plastics and far less copper used than the old days heavy ceramic ones, it obviously cannot handle a slow overload, which I personally think it should be tested for also, but thats modern crap for you
Just looking at the fuse itself, and the contacts, it all looks a bit out of proportion, doesn't it? But hey, it's good enough, and you get what you order... Or, don't get a midget fuse for a giant load.
In one of our machines installed fuse base circuit breaker installed. The fuse of the breaker burnt now is not available in the market. My question is will we may replace it with MCB(on/off option manual).
That fuse holder was NEVER a fire hazard. They are specifically engineered not to catch fire. In fact, even with a blow torch you might get it to smoke and smoulder, maybe even catch fire... but it would almost immediately self-extinguish (as per electrical standards).
I was wondering exactly this, no mention of 'rating of circuit breaker suitable for cabling given distance and derating factors, voltage drop, prospective fault current, disconnection time, etc...'........ Can be dangerous to carelessly uprate a circuit-breaker!
The lift is 3 phase, the building only has single phase, and it's currently connected via a phase converter. Been like that since it was installed 7 years ago. Further work is required there.
Was this a single phase circuit? Lift current=60A is a very large current for 240V (>14kW). That's a huge single phase motor. In Australia 240V is limited to 15A (3kW). Anything more has to use 3-phase.
Were these kinds of fuses the next model after rewirable fuse boxes and before consumer units? I remember the old ones years ago where you had to thread the fuse wire of the correct amperage back on if it had blown.
Cartridge fuses were available at the same time as rewireable types, they overlap was many decades at least. They were not as common, as they cost significantly more.
Very good that you demonstrated the dangers of moderate overload. I have always advocated over specifying - e.g. I never used 1mm sq. t&e for 6a lighting circuits in domestic premises - I always used 1.5. Always used 6mm for 32A cooker circuits. My parents’ house was a shocking example: the lighting circuits, wired mainly in vir/cotton single cores in slip conduit, with porcelein rewireable fuses rated at 5a, had been wired with three 5a fusewires BY ELECTRICIANS to stop the fuses from blowing. Bits of pvc 3/0.29 had been joined onto the old cables when a new d.b. had been installed - and the pvc had melted. Amazing that there had never been a fire. My great uncle, an architect who emigrated from Germany before ww2, told me that a colleague said that, given the standard of electrical installation, it was a miracle that london had not burnt down.
I think you will find the brown marks in the CB are from arcing when the CB tripped until it was suppressed by the arc quenching device (finned device above brown marks).
With these devices, they were all working on their limits or above with no margin for any overload.Price can govern safety where a lot of people are concerned and compulsory 2 year inspection tied to insurance would uncover some dubious installations and prevent incendiary situations occurring.
I got a haul of old fuses the other week. Are these still in use? Are they worth anything? All checked OK for continuity. s23.postimg.org/4p6ql1qvf/Fuse_Haul.jpg
