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Other Vintage Household Electrical or Electromechanical Items For discussions about other vintage (over 25 years old) electrical and electromechanical household items. See the sticky thread for details. |
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25th Apr 2018, 9:33 am | #81 |
Dekatron
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Location: Warnham, West Sussex. 10 miles south of DORKING.
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Re: Vintage BS1362 plug fuses
Interesting to read about the non standard BS1363 fuses fitted to 13amp plug tops.
A few months ago I discovered my Gran's old bathroom heater. This type of set up would not be allowed today of course. She used to hang it from a cup hook over the bath. I cannot understand why she had this odd fuse arrangement. She was quite a gal my old Gran and no, she did not electrocute herself. She passed away at the age of 88 after suffering a heart attack while riding her Harley Davidson Panhead around the Silverstone Circuit in 1958. She would be delighted to know her handiwork still functions. Thinking about it Gran was a bit colour blind, discovered when she applied to be a Lancaster bomber pilot in WW2, so this might explain the odd fuse set up. Byeeee. John. |
25th Apr 2018, 7:35 pm | #82 |
Heptode
Join Date: Dec 2010
Location: Barnstaple, N.Devon, UK.
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Re: Vintage BS1362 plug fuses
Hi John. I've got to know, how is that wired in the plug then? In series ? Or was the fuse intended for some other purpose as in, there's no fuse wire in it but the pins are used for something to connect to.
Looks a bit like a foreign torture instrument, not that I am suggesting your Gran would be involved in such things. Also, is it just the picture or is it really glowing white hot! ? It all reminds me of the Black Books sketch https://www.youtube.com/watch?v=Gf74JmBiPto David. Last edited by teetoon; 25th Apr 2018 at 7:51 pm. |
25th Apr 2018, 9:56 pm | #83 |
Hexode
Join Date: Oct 2010
Location: Box End, Beds. UK.
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Re: Vintage BS1362 plug fuses
30+ years ago I worked in a building where all the mains sockets in one room were plugged into a single 13A socket in the adjacent room, with a13A fuse in the plug. We had a wall mounted fan heater, 2KW I think, and an electric kettle. We tried to remember to unplug the heater before having a brew, but we sometimes forgot, but anyway the 13A fuse survived long enough for the kettle to boil. It must have aged it a bit each time, because periodically it would expire with this treatment. I dread to think how hot the plug got, because many 13A plugs carrying 3KW continuously get too warm for my comfort.
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25th Apr 2018, 10:47 pm | #84 |
Pentode
Join Date: Apr 2018
Location: Tyne and Wear, UK.
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Re: Vintage BS1362 plug fuses
I was looking on a web site about Pat testing, and they claim a 13amp fuse does not blow at 13amps, but can handle 20amps continuously. If that is true, that can't be safe. The cable will have melted long before the fuse would blow. I am not even sure what size cable can handle that kind of current. Maybe 2.5mm. Surely a continuous current of 20amps from a 13amp fuse would generate heat, and possibly melt a plug. Would the fuse only blow from a huge electrical surge ?
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25th Apr 2018, 11:21 pm | #85 |
Dekatron
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Location: Leominster, Herefordshire, UK.
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Re: Vintage BS1362 plug fuses
Cable rated for 13A will get hot at 20A but it will be nowhere near melting. In any case, unless you're doing something daft, the chances of a fault causing a long term overload are pretty small. A short which will happily take out the fuse or an open which won't matter are far more likely.
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26th Apr 2018, 12:35 am | #86 | |
Octode
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Re: Vintage BS1362 plug fuses
Quote:
It is therefore very important to guard against the possibility of being able to overload the 13A plug. The fusing characteristics of fuses and the tripping characteristics of circuit breakers is a complex area. The wiring regulations have tables & graphs showing these characteristics for all the different types of fuses & breakers. So for a given overload, you can tell how long the device will take to interrupt the current. Fuses are not the simple devices people think they are!! All the best Nick |
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26th Apr 2018, 8:01 am | #87 | |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
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Re: Vintage BS1362 plug fuses
Quote:
This is how it looked with flash. John. |
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26th Apr 2018, 8:17 am | #88 |
Hexode
Join Date: Oct 2010
Location: Box End, Beds. UK.
Posts: 271
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Re: Vintage BS1362 plug fuses
"Fuses are not the simple devices people think they are!!"
The problem with fuse are that they are simple, they simply use I squared R for time T to melt some metal; there is no "magic" at just over their rated current that will cause them to rupture at exactly a prescribed current irrespective of time. Some do have dual elements and suchlike to modify their characteristic, but fundamentally it all comes down to heat in the fuse A fuse rated at X amps will carry X amps almost for ever, but will not fail at X + small percentage at all quickly, if at all. Whether it was by design, or not, I don't know, but the fact that the 1" fuses that fit in 13A plugs are virtually unique to the application prevents the wide variety of fuse characteristics that are available in 20mm and 1.25" fuses being used in them. I agree though, that the selection of fuses is not simple, unless odd sizes are required (as in 13A plugs) which greatly limits the options available. Ian |
28th Apr 2018, 5:04 pm | #89 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
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Re: Vintage BS1362 plug fuses
Here ia one that came out of a plug on a new gas hob igniter.
The plug itself is nylon and of reasonable quality. It is branded MS. The fuse is another story... |
28th Apr 2018, 6:09 pm | #90 |
Dekatron
Join Date: Nov 2009
Location: Lincolnshire, UK.
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Re: Vintage BS1362 plug fuses
I've certainly seen fuses like that one shown above, and quite a few years ago, too.
I'll have to check through a few of my spare fuses and see what I can find. |
28th Apr 2018, 6:23 pm | #91 |
Dekatron
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Location: Brentwood, Essex, UK.
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Re: Vintage BS1362 plug fuses
Those fuses are really dangerous. Dad bought some like that from a market stall n the 1960's. One was fitted to mum's electric iron, and in the early 1970's the insulation of its flex failed. From the after-effects, the wire in the fuse vaporised and blew holes in both end caps, filling the inside of the plug with copper vapour. It did not interrupt the current so there was a first arc in the cable in series with a second arc in the plug, the arcs limiting the current so that the 30A fuse in the switchboard didn't blow. Mum was using it at the time and had the presence of mind to rapidly pull out the plug (the socket was unswitched). I immediately; checked all our plugs and found half a dozen that I replaced with proper ones.I still have the old ones, kept in a bag labelled that they are not to be used. They are only marked with the current and do not purport to be to any standard.
Last edited by emeritus; 28th Apr 2018 at 6:30 pm. |
28th Apr 2018, 10:18 pm | #92 |
Dekatron
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Re: Vintage BS1362 plug fuses
I heard the bang and got to see the aftermath of one blowing.
The boss at work tried to help in production and got a switch wired wrong. The fuse only had about half of one of the end caps remaining. The 30 amp fuse did not blow either. |
28th Apr 2018, 10:42 pm | #93 |
Heptode
Join Date: Apr 2008
Location: Eastbourne, East Sussex, UK.
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Re: Vintage BS1362 plug fuses
Agreed on 13A fuses needing a lot more than 13A to blow. At a previous place of work it was common for the dishwasher and kettle to be used at the same time while plugged into a 4 gang outlet, the fuse never blew but the four way socket eventually melted!
I have an old Black and Decker 1200 W heatgun here, I recently put a new 13A plug on it as the original had become damaged. The original 1970s plug had a 3A fitted fuse which had never blown despite passing around 5A every time it was used, often for several minutes at a time. I use 1A fuses on kit which only takes a small current but even these would probably take a fair overload before blowing in the event of a fault such as shorted turns on a mains transformer. |
28th Apr 2018, 10:56 pm | #94 |
Dekatron
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
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Re: Vintage BS1362 plug fuses
I used to use 1A or 2A fuses for table lamps. This was fine when I used bulbs from Woolworths as they had fast-acting Ballotini fuses. When I had to use bulbs by other makers that only have simple wire internal fuses, the plug fuse always failed as well when the bulb blew, necessitating the fitting of 3A or 5A fuses.
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29th Apr 2018, 5:28 pm | #95 |
Hexode
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Location: Weymouth, Dorset, UK.
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Re: Vintage BS1362 plug fuses
My old oscilloscope has a black 10 amp fuse in its plug even though the scope's own fuse is 3.15 amp. I noticed the scope has a significant inrush at each switch on so I'm guessing its own fuse is a slow blow or something similar. I once had a black 13 amp plug given to me it had a removable top so you could change the fuse but still needed the screw in the base removed to wire it never seen one like it anywhere else. When I got it it had a blue 3 amp fuse in it. I've still got it somewhere but not sure where.
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30th Apr 2018, 11:25 am | #96 |
Rest in Peace
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Re: Vintage BS1362 plug fuses
Cable rating is based on the use of real-world fuses and circuit breakers. It is accceptable to protect 1.25mm² flex, rated at 13A, with a 13A fuse, for example. Although the fuse will carry in excess of 13A, the curve of current vs. time before the fuse blows has been taken into account when stating that the cable may be used for applications demanding 13A.
Re 15A and 20A 'plug fuses', these are unacceptable and dangerous in the UK wiring system, not least because other components such as the fuse clips and socket contacts may overheat at higher currents. Other countries in the world use UK-style electrical accessories, e.g. Malaysia, Hong Kong, Cyprus, Malta and Malaysia. Their standards and methods may differ, and their plugs may not meet BS1362, but they still take the familiar 5x25mm fuse which is why such things exist. In a similar vein is the 'plug key' that defeats the shutters of a BS1363 socket, to allow insertion of a 2.5A Europlug. These nasties can be bought in some of the countries that use BS1363 sockets, but I won't say any more about them. There are situations where the plug fuse is intended to provide short-circuit protection only, not overload protection, and in these cases the fuse and cable size may appear mismatched. A 0.75mm² flex, rated at 6A, might be fitted with a 13A fuse on a fridge, for example, to allow for the compressor starting surge. The fuse would not protect the flex against longer-term overload due to the compressor motor burning out, but it will still adequately clear a short-circuit fault due the flex being crushed or severed. Overload protection is provided by the appliance manufacturer in the appliance itself. Countries that do not use fused plugs (most of the world) take advantage of the fact that modern appliances contain their own overload protection, and give protection to the flex against short-circuits by the fuse or circuit-breaker in the distribution board. On the common 15/16A circuits used worldwide, 0.75mm² flex requires no additional protection, so this is the smallest standard flex size now used in Europe for example. The old 0.5mm² that we used in the UK for table lamps and similar and rated 3A, that required protection by a fuse in the plug smaller than 13A, would not be permissible in the absence of a plug fuse. This brings us to an important point about fused vs. unfused plugs: The main advantage of wiring systems with fused plugs is not that they are much safer, as many people believe, but because they require fewer wiring circuits to do the same work. One 32A circuit is more flexible than two 16A circuits. For example, how would you power three heaters each taking 10A? One 32A circuit can do it, but two 16A cannot. Even with three circuits, you have to be careful which points you use, not connecting any two heaters to the same circuit. Furthermore, by the application of diversity, one allows that not every piece of equipment is in use simultaneously in real world situations. If only 75% of the load is likely to be used at once, under worst case conditions, the 32A circuit allows for 4 heaters to be on the premises, while the diversity adds nothing to the 16A circuits because they still can't support 75% of three heaters rounded up to the nearest heater. The benefit of the larger circuit comes at the cost of needing fused plugs, as the appliance flexes are not protected by the 32A circuit fuse. Fused plugs are at risk of abuse by unskilled users, and any but the best quality are at greater risk of overheating than unfused plugs allied with protection in the consumer unit installed by the electrician. In our niche application we like to provide the best protection for our aged sets and appliances and their surroundings and users, but it's important to see the big picture of the function of plug fuses in allowing greater circuit flexibility. This was the very point made when the ring circuit was introduced in place of radial, although the ring configuration is a separate issue and the advantages of large circuits and fused plugs apply to any circuit topology. Last edited by Lucien Nunes; 30th Apr 2018 at 11:38 am. |
30th Apr 2018, 12:33 pm | #97 |
Octode
Join Date: Mar 2006
Location: Co. Durham, UK.
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Re: Vintage BS1362 plug fuses
Ring Circuits are an economy measure. That's what they were designed for, and that's why they are still popular.
Fused Plugs can be useful. On a 'proper' installation, with 'one socket, one fuseway', a fused plug allows the use of a low-power appliance such as a table lamp, without going to the fuseboard to change the fuse. Has anyone found the reason why a filament lamp blows the fuse when the filament itself disconnects, but not when the switch is opened? They never used to. |
30th Apr 2018, 12:38 pm | #98 | |
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Re: Vintage BS1362 plug fuses
Quote:
I put it down to the spark generated when the filament broke ionising the gas in the envelope and effectively short circuiting the lamp.
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30th Apr 2018, 12:40 pm | #99 |
Dekatron
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Re: Vintage BS1362 plug fuses
A very useful synopsis there, Lucien, many thanks for taking the time to write it.
N. |
30th Apr 2018, 12:43 pm | #100 |
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Re: Vintage BS1362 plug fuses
Yes it can draw an arc between the filament supports. Better lamps contained a rapid 'Ballotini' glass-bead-filled fuse in one or both leadouts - not sure about today's store-bought lamps though. I believe it was more of a problem on DC and recall the owner of a house served by both DC (generated in the old mill on his property) and AC (bought in from the grid) that when he switched some of the lighting from AC-only to either/or, he changed some of the light switches to fused connecction units due to the increased tendency of a failed lamp to take out the circuit fuse.
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