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Author Topic: Fuses  (Read 1274 times)

sevenlayermuddle

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Re: Fuses
« Reply #15 on: November 25, 2020, 08:56:57 AM »

Must admit I am capable of worrying, a lot, about white goods starting fires.  I try not to leave things on when I am out, or even when I am bed, but that tactic is hardly applicable to things like fridges, freezers and boilers.  And anyway, a kitchen fire could take hold when I’m simply watching TV.

I was brought up in Glasgow in what was then called a Corporation house (‘council house’ now).  There was no central heating and Dad had a routine of going to bed last and on his way upstairs, he’d turn off the gas supply at mains.   When I was younger electricity also used to get switched off at the mains overnight, although he had to give up on that when we got our first fridge.

Irony is, the cupboard where the gas valve was always smelled of gas.... I suspect it was never designed for twice-daily use and after a few years, maybe the seals had weakened?
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Weaver

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Re: Fuses
« Reply #16 on: November 25, 2020, 03:27:26 PM »

I think your dad was a pretty wise chap.

A thought occurs to me for an electronics project, an infra red directional sensor that can be pointed at white goods, like a camera. If it detects a temperature rise, it turns off the mains to the appliance. Could be coupled with a smoke detector perhaps?
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g3uiss

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Re: Fuses
« Reply #17 on: November 25, 2020, 04:11:30 PM »

@7LM. I don’t think your memories are all that unusual. When I was young my Dad turned off gas and electric when we went away for more than a day, which meant mum had to empty fridge. However we had a “Larder” then and most of it went there. I must confess we still turn most electrical appliances/ sockets off while we are away any significant time, except my servers !

Tony
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Chunkers

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Re: Fuses
« Reply #18 on: November 26, 2020, 12:00:26 PM »

Just wanted to make the point that RCD type devices are much faster to react to a fault than a wire fuse and the speed is part of what makes them much better at protecting people / things.

In theory an RCD can react fast enough to prevent a fatal shock in some circumstances, a fuse does not do this. Personally I don't using lower rated fuses necessarily helps, each device should have a fuse appropriate to its service e.g. devices up to about 700W should have a 3A fuse.

Sorry if I am stating the obvious here  :blush:
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sevenlayermuddle

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Re: Fuses
« Reply #19 on: November 26, 2020, 01:10:38 PM »

RCDs are different devices, serving mainly to prevent electrocution.  They  do nothing to stop large currents from flowing on the live-neutral circuit, you still need a fuse or MCB for that.

For fire protection, one interesting enhancement might be an Arc Fault Detection Device, as a fire is just as likely to be caused by arcing at a poor joint, but such arcing won’t blow a fuse and won’t trip an RCD.

I think AFDDs have been common for a while in some parts of the world, but don’t yet seem to have caught on here.

Following link is not a site I’ve ever visited before, just a random Google hit for AFDDs, but quite informative...

https://www.electriciancourses4u.co.uk/useful-resources/what-you-need-to-know-about-arc-fault-detection-devices-afdds/
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Ronski

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Re: Fuses
« Reply #20 on: November 26, 2020, 01:22:12 PM »

We recently had a PSU in a small computer fail with a cloud of smoke, the MCB and RCD tripped, although I can't be 100% certain on the RCD as only daughters were home. The fuse hadn't blown.

Whenever we go away I always turn off as many plug sockets, bathroom extractors etc as possible, we often empty and turn off one of the two fridge freezers as well. I also turn the water off, my wife always told me it was a waste of time, that is until one of her mates came home from holiday to a flooded house, then she finally realised there was sense in my madness.
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tiffy

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Re: Fuses
« Reply #21 on: November 26, 2020, 02:02:59 PM »

@7LM:
Interesting reading ref. AFDD's, thanks for the link, was not aware of these devices but can see perfect sense in the philosophy.

When I had my consumer unit replaced a few years ago, old unit still had wired fuse carriers and no RCD protection, I opted for individual circuit RCBO's, a bit more expensive to populate than the more common split circuit RCD arrangement but in my opinion worth the additional expense and RCBO's have certainly come down in cost now with their more common deployment.
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tickmike

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Re: Fuses
« Reply #22 on: November 26, 2020, 08:17:01 PM »

Another thing I have found that makes a fuse seem warm/hot is the connection being loose !.
Eg in a plug top the wire/s are loose making small arc's and heating the fuse and maybe the whole plug warm.

A few years ago the Electric supply company put a new electric meter in and main 100 Amp main fuse unit.
For some time later I kept getting a 'Odd Smell'  :( .

Did you know the Human Nose is good for detecting electrical problems  :hmm:.

After having a good sniff around the consumer units and all other electrical power supplies in my equipment cupboard the last thing was this new 100A supply fuse, bingo the smell was coming from there but only when say the cooker was on (larger load) .
So doing the unofficial way :-\ got my Insulated electrical work gloves on and insulated tools tightened the loose 'Live' connection in the fuse unit, we never had any more problems with it  ;).
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4candles

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Re: Fuses
« Reply #23 on: November 26, 2020, 08:18:06 PM »

An interesting site, 7LM, containing sobering statistics -

Quote
In 2016/17 there were 30,322 fires in domestic premises in England alone, of these 17,743 had an electrical source of ignition. Faulty or misused appliances, cables and equipment made up 10,982 of these.
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tiffy

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Re: Fuses
« Reply #24 on: November 26, 2020, 09:05:14 PM »

Quote
So doing the unofficial way :-\ got my Insulated electrical work gloves on and insulated tools tightened the loose 'Live' connection in the fuse unit, we never had any more problems with it  ;).

Surprised you could carry out this activity as the main supply fuse carrier is (or should be) sealed with the screw terminals being integral and only accessable with the fuse removed.

Perhaps the electricity supply tech. who replaced the meter failed to re-seal the fuse?
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burakkucat

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Re: Fuses
« Reply #25 on: November 26, 2020, 10:15:30 PM »

Perhaps the electricity supply tech. who replaced the meter failed to re-seal the fuse?

Over the years, I have come accross three separate occasions of that fact!
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sevenlayermuddle

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Re: Fuses
« Reply #26 on: November 26, 2020, 10:45:10 PM »

A few years ago, I had to have the consumer unit main RCD replaced as,  *when I pressed the ‘test’ button it failed to trip.

A respectable local electricians company did the work.  In order to make the CU safe for them to work on, they simply cut the security seal and pulled the main supply fuse, in the meter box. 

They assured me it was normal practice and that the distribution company would ask no questions.   The meter has been read umpteen times since then, and nobody has commented on the broken seal.

* speaking of pressing that test button, I assume we all do so every few months, or as stated on the label in the CU?  The guys who fixed mine praised me for doing so, but they also confessed I was the first person they had ever encountered who asked for a repair simply because the ‘test’ failed to trip. :'(
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tiffy

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Re: Fuses
« Reply #27 on: November 27, 2020, 12:18:48 AM »

Quote
They assured me it was normal practice and that the distribution company would ask no questions.   The meter has been read umpteen times since then, and nobody has commented on the broken seal.
Yes it happens and I don't think the network meter reader would really give a toss, however, depending on your area and the visiting tech I suppose, the network electricians can be snotty should they ever have occasion to visit and find an unsealed main fuse.
Certainly in "tickmike's" case where the meter was replaced the tech should have replaced the main fuse seal.

Quote
speaking of pressing that test button, I assume we all do so every few months, or as stated on the label in the CU?
Very few do of course, perhaps another good reason to fit RCBO's where individual circuits can be periodically tested in a more controlled manner without tripping half the consumer unit in one go.

Would that turn the average householder into a diligent checker, human nature being what it is I doubt that very much!
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Alex Atkin UK

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Re: Fuses
« Reply #28 on: November 27, 2020, 05:58:19 AM »

Very few do of course, perhaps another good reason to fit RCBO's where individual circuits can be periodically tested in a more controlled manner without tripping half the consumer unit in one go.

Indeed, having trained as an electrical engineer I still never test the RCDs as its hard to find the right time when all sensitive devices can be turned off so tripping it off and on again doesn't damage something.
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sevenlayermuddle

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Re: Fuses
« Reply #29 on: November 27, 2020, 08:39:49 AM »

Trouble with not testing RCDs is they need the exercise, else the mechanism may seize in the ‘on’ position, meaning they are no longer providing protection.  That was probably why mine was found to not be working... it simply hadn’t tripped for a few years, and had got sticky.

That said, the RCD test button works by putting a resistor in the leakage circuit.  If it fails to trip, as is more likely if it hasn’t been regularly tested, the resistor stays in the circuit and will quite quickly overheat.  When discovering my own failure I just got a puff of smoke as the resistor burned out, but I believe they have also been known to even catch fire or ‘violently explode’.    :o

So there is an argument that says, if you’re not in the habit of testing, it is worth doing so with some caution.  Or might even be better to get an electrician to test them first, before changing your habits.

My view on damage caused to equipment by testing RCDs...   If anything is likely to suffer damage from manually testing the RCD then that thing will be damaged quite soon regardless, because I can’t stop unplanned power cuts from occurring.   
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