I used them when I spent a couple of weeks working for an electrician when I was in the 6th form, that would place it in
1963.They were called "Scruits" (TM)
I'm fairly sure I've recently seen them inside multiple ceiling light fittings (3-lights etc) and ceiling fans.
DG
Yes, that's a tradename. "Dogs Bollocks" was a nickname, which came about due to the way a pair of them would dangle below a cable knot.
I have a number of old books on wiring (stangely, I find the history of it interesting). The most recent one with any reference to this type of connector is about 1935, and that's only in a picture -- I suspect thet were probably rather obsolete even by then. Ceramic chocolate block connectors were well established by then, together with a one terminal single ended chocolate block connector which looks like a screwit but cylindrical rather than tapered. Oh, and today's circular junction boxes with the slotted terminals just start appearing (with screwed lids at that time).
Those are single-ended insulated crimps, which look similar but are _far_ more reliable...
I had an electrical wiring book in the mid 1980s which recommended them. Can't remember which one though.
Owain
I've never seen the point either. Unless in a 45th floor apartment with no rubbish disposal facilities.
The Saniflo is not the only waste disposal device invented by a Frenchman. google Garchey - I think the first site is the Barbican Estate Underground page, will tell you all you didn't want to know.
Owain
Well, there are loads of books which recommend them in 2005 too, to Americans...
My Mum lives in a tiny town house with no (private) garden. In the summer, the temperatures stay > 30 deg C for days on end. A garbage disposal is essential.
Yebbut this was a British book, and referred specifically to Scruits for doing loop ins in lighting circuits.
I have some genuine glazed porcelain scruits and find them preferable to any plastic imitators.
Owain
You're cruel to your mum. I hope she cuts you off without a penny. With your vast house you must have room for a granny flat. ;-)
Hi,
I will assume that your post is not bait and is serious
NOT TRUE
1.General use U.S. Circuit breakers have always been thermal/Magnetic.Not True. Mr. Edison picked a voltage and he used that voltage (Direct Current, of course). Edison's first great central station, supplying power for three thousand lamps, was erected at Holborn Viaduct, London, in 1882. Does anyone know the voltage that was used? In any case the U.S. Voltage is due to historical factors. I am sure the British voltage was not selected much more recently.
NOT TRUE. You are making multiple invalid assumptions.
It seems you contradict yourself.
Not True. In the U.S. this would be a 240V 15A circuit! Except for special use such as a medium sized Caravan. or some other use that REQUIRED less than 240V.
I would be very surprised to find an impedance that high. Reasonable scenario:
500' feeder cable to building .063 ohm (3/0 Aluminum, approx. 68mm) 200' circuit wiring .242 ohm (10gauge, approx 5.25mm) comes out to .305 ohm providing about a 400amp fault. The voltage drop at the distribution transformer would be much less than 5% and therefore would have little influence. This is low enough to still be in the thermal range of the Circuit breakers trip curve and would open in less than .7 seconds.Example of real world circuit (an outlet in my Kitchen):
20amp circuit breaker Underground feeder cable from transformer .00605 ohm (100' 350kcm Aluminum, approx 177mm) Feeder from Main to Sub Panel .006128 (80' 3/0 Copper approx 85mm) Circuit wire to outlet .198 ohms (100' 12 gauge approx 3.3mm) Total impedance .210 ohms fault current 570amps (about 28x rating) Circuit breaker is in magnetic area of curve and will open in maximum 1 cycle (1/60th of a second)ALL U.S. general purpose circuit breakers are Thermal/Magnetic!
Note: Our circuit breakers magnetic trip are similar to your type D
Slightly Lower. The U.S. nominal was raised to115V/230V before WWII It was re raised to 120V/240V in the 70's and is now specified as a maximum of 125V/250V Nominally 120V/240V unloaded voltages near 125V are common.
Again, in the U.S. a 3kW circuit would be 240V 15amp and the same benefits would apply.
Please quote sources for statistics.
The common cable in the U.S. is the same PVC stuff you use except for color. We are more conservative in ratings 14gauge (2.08mm) is rated at 15amps, 12 gauge (3.31mm) is rated at 20amps. These are used for residential general use circuits. A cooker would use 6gauge (13.3mm) at 50amps (240V). The trend is to premium 90degreeC rated cables used at these same ratings.
Why Not?
Huh?
We have what you call TN-C-S or PME
Earth is Earth, Neutral is Neutral, they are bonded at the Service Entrance ONLY!
In the past it was permitted for the neutral to be used to ground the frames of ranges and dryers. This came about as Interim Amendment No. 53 put into effect on July
10, 1942. This was to allow the neutral to ground the frames by means of a bonding jumper from the frame to the neutral. The reason for the amendment was to save raw materials like rubber and copper for the effort of WWII. This special amendment however was not removed from the NEC until the 1996 code cycle. This one amendment has caused quite a bit of problems for the DIY. Some have assumed that the neutral and ground must be the same and have used them as such. Others have never given a thought about the bonding jumper and left it intact in a 4 wire circuit. This results in parallel current flow on the neutral and ground. In a sub panel this can be troublesome. Note: the proceeding three paragraphs are from the Internet (not my writing)Don't ever accuse us of not making sacrifices ;
It is called flexible conduit and there are actually quite a few restrictions. In this application a six foot max length is a big one. It is primarily used to connect the fixture in the suspended ceiling to the fixed wiring of the building. Six foot long pre wired assemblies are sold and some fluorescent suspended ceiling fixtures come with the whip pre-attached.
A similar but different product, BX or armored cable, is sold in rolls and is the equivalent of metal jacketed 2T&E and is installed similar to 2T&E it is popular in NYC because Rats can't chew through it.
Jim Remove SPAMX from email address
You make some good points, but there are a few I'll pick up on:
true, at least compared to UK. Maybe not the world, US seems the model of good practice compared to African practices, and that of many other countries.
but this doesnt change the fact that 110 is inherently more dangerous than 240. With 240v we treat it with respect, with 110v people relax since it wont electrocute them, and hurts waaay less if they get bit. They worry less about cord grips etc. The result is fires, which are the prime killer, not electrocution.
still cant figure out what you mean there. For a given load you do have higher i with lower v, and each load is on 1 circuit as far as i can see.
I dont think that was the assumption: the problem is simply theyre designed to have a higher incidence of faults. The practice of push-in connection on mains sockets is something considered unthinkable here, for good reason. Use of single insulated mains flex has been illegal for decades, etc etc.
we know its due to many factors.
no contradiction there that i see, just an example of how higher v gives a safety benefit.
should give less nuisance trips, ours sometimes trip on bulb failures.
In US IIUC it would be called 240v, but in fact be 120-0-120, so the voltage from earth is 120 ac, not 240. In which case the fault clearance benefit of genuinely 240v would sometimes apply and sometimes not. Some faults that smoulder at 120 can arc over and trip at 240.
they were banned here long ago because they cause connection failures and fires. They dont provide anywhere near the clamping pressures of our screw connections.
snip
that much is fair enough, but...
remarkable. At least not something normally permitted here. But we do have a permited 2 conductor wiring system, I forget the details, ISTR maybe it uses MICC? I'm not sure, but I'm pretty positive there still is one here, but it is not AFAIK permitted in domestic premises.
snipped-for-privacy@meeow.co.uk wrote: > remarkable. At least not something normally permitted here. But we do
TN-C. Earthed concentric wiring (MICC). Very limited applications, usually restricted to private generating plant or private transformer supply. Not necessarily banned in domestic premises though, AFAIK.
Owain
In any
Both the US and British voltages are a result of history. The British started with 100V IIRC, (100V was picked (by Edison)as it is a nice round number!) then moved up to 220V DC as it was cheaper to distribute power at the higher voltage. Parts of Camden Town in London were only converted from this in 1958. When the power supply world moved on, in the UK, AC was introduced and AIUI the available transformer stampings were optimal at 50Hz. The US came in with AC a bit later IIRC, and by then the laminations would sustain 60Hz, reducing the transformer size( & cost) and centre tapping the 230V allowed the use of the old distribution circuits and products without upgrading. If we were starting again today the world would probably settle for 230V @ 400 Hz, giving smaller ( &cheap) transformers without significantly increased losses.
The US consumer has a product penalty as a result of using 230V, in that 2KW per 120V appliance is probably a realistic limit for the house wiring used, hence electric toasters and kettles are a pale shadow of the European ones. Also DIY tools, just do not have the "grunt" achieved by 230V. Dishwashers also are frequently hot fill. However 240V centre tapped is a lot safer than 0 - 240V IMO. US wiring is, I believe, produced to a higher temperature performance specification than Europe. Certainly this is true for internal wiring in consumer products. Having experienced US wirenuts, I can confirm that they are a fire on the way to a happening with solid cables and would never be accepted in the UK. US wiring in conduit is much safer from an accidental shorting viewpoint than UK wiring just buried in walls and if conduit wires are used, is much easier to modify.
I believe the UK has very acceptable standards for wiring, but would probably benefit from using a 120-0-120V system on the grounds of safety and has gone over the top on equipotential bonding. On a basic level, who cares if the fault current is not sky high as long as the trip works!
Just a few comments
Regards Capitol
>
I don't know what frequency (or voltage) he used but Tesla's company distributed AC mains in the US before it reached Europe.
Edison decided dc was superior, and many a battle was fought over ac vs dc. It didnt take long to realise Edison had not made a good judgement on this point, but he continued his marketing battle by publically electrocuting animals on ac current for entertainment.
NT
On Sat, 18 Jun 2005 22:58:54 +0100,it is alleged that "Mike" spake thusly in uk.d-i-y:
[snip]
From
"It is generally accepted that Nikola Tesla chose 60 hertz as the lowest frequency that would not cause street lighting to flicker visibly. The origin of the 50 hertz frequency used in other parts of the world is open to debate but seems likely to be a rounding off of
60hz to the 1 2 5 10 structure popular with metric standards."From my own knowledge I am fairly certain that a German company was responsible for the usage of 50 Hz in Europe, it may have been Siemens, but my memory is fallible :-)
In any case, in a region like Europe, having a well established AC system of one frequency in the area would tend to encourage the usage of that frequency elsewhere to facilitate crossover of equipment and appliances, thus leading to savings in various things I slept through in economics class;-)
Most of the early generation was at 100V. It suited arc lamps and the filament lamps of the time. Trouble was it wouldn't reach further than a few city blocks. I don't think there's any real concensus why many of the UK power stations switched to 200V and the US didn't, but one reason which does seem to have more credibility than others is as follows. Very early on, many London boroughs banned overhead cables (and those bans are still in effect today). This forced the cabling to be underground in much of London, but it was mostly on poles in the US at the time. Now what do you do when you have a local supply infrastructure that no longer meets the local demand? In the US, it was easy, you just string thicker cables on the poles. In London, with the cables all being underground, this wasn't possible without doing a complete new installation. So the way round the problem was to double the voltage, and we got lots of 200V supplies. Over the years, the voltage has continued to creep up in small increments. By the late 1950's, most of the UK mains final supply voltage was in the 200-250VAC range depending what town you lived in, and it was all changed to 240VAC in the early 1960's. Some areas with lots of cinemas also retained DC supplies for some commercial customers -- much of central London had a 220VDC supply until the late 1970's.
400Hz severely reduces the maximum area of a synchronisation zone, which makes carrying power any distance very much more expensive. Many of the 50Hz zones are close to their size limit now, so I don't think anyone would think of distributing at any higher frequency in Europe. It would be OK on a small isolated island. 400Hz isn't suitable for industrial motors either. Actually, supplies to large commercial customers at 16 2/3rds Hz and 25Hz used to be quite common as they much prefer a lower frequency for large motors. Transformer size is really only an issue on planes and boats, which often do use 400Hz.
Well, because it clears the fault more reliably and leads to fewer fires and deaths?
Christian.
Where is the evidence for this? Most fires are due to poor connections, they won't necessarily trip the breaker until much too late!
I noticed some comments earlier in the thread on the phasing problems of 400Hz. There are no problems if the main distribution system is HVDC. This is why major power links have been HVDC for many years AIUI. The
50Hz local distribution system is purely historic and well entrenched but the transformer sizes could be substantially reduced with 400HZ. In the US, local transformers on a pole appear to be the norm in a lot of areas. These would certainly be lighter at 400Hz. The 400 Hz suggestion comes from discussions with US engineers many years ago on which way would you go today if you could start again. I certainly like it. I haven't kept up to date with the power side of electrical distribution for a few decades, but sub 50Hz supplies were normally achieved locally by six and twelve phase transformers with interphase reactors, and not generator sourced. Sub 50Hz harmonics can be a major headache for distribution transformers AIUI so local generation seems essential.Regards Capitol
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