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Old 15th Jun 2022, 4:19 pm   #61
Richardgr
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Default Re: Tin Foil - makes you weep

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...
In times-past I pondered about the idea of something like an IEC309 'kettle-lead' socket as a successor to the BS1363 plug/socket: You could fit 5 of them into the profile of a dual back-box, even if you include an in-box fuse in the profile.
That's what makes a Swiss 3 pin plug such an elegant solution ...
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Old 15th Jun 2022, 4:24 pm   #62
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Default Re: Tin Foil - makes you weep

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Because their final circuits have protection rated at 16A, which is sufficiently low to trip safely and protect wires down to 0.75mm sq ...
That isn't the regulations. Over 10A must be 2.5mm2, 10A is 1.5mm2, and 6amp (lighting) also 1.5mm2.

Each block of circuits has its own RCD, so that nuisance trips do not interfere with critical circuits (e.g. bulb blowing).

All circuits are max 10A unless it is a feed to a cooker or other high powered device, which is 3 phase @ 16A per phase in my house, but could comfortably be 10A.
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Old 28th Jun 2022, 2:46 am   #63
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Default Re: Tin Foil - makes you weep

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My grandmother lived in a 1930's semi in North Manchester.
It had a large metal-clad double-pole fuse box with radial wiring to Wylex sockets.

I don't know the reason for the DP board, I'm sure it was never a DC supply, I imagine it was a case of what was available.

She moved out in the early '80s and I suppose the place was rewired, but sometime before then I put heavy gauge wire in the neutral fuses and marked them NEUTRAL LINKS DO NOT REMOVE.
Some early AC supplies also needed double pole fuses, if both poles of the supply were live.
Consider for example a system with 3 phase, 4 wire mains at 127/220 volts. A consumer requiring 220 volt supply would be connected between any two phases and would need double pole fuses as either pole was live at 127 volts to earth.
Later the supply might be modernised and changed to 3 phase, 4 wire at 220/380 volts. The supply company would change the connections at the service cut out in order that the consumer still received 220 volts. The existing two pole fuse boxes would likely remain.

Other systems might have been single phase, 3 wire at say 120/240 volts. Consumers requiring 240 volts would then be connected between both poles of the system and need double pole fuses.
Later the supply company might double the voltage to 240/480 volts and change the connections in the cut out in order that the load is now between the previously unused center wire and one pole of the supply. The old double pole fuse boards would remain.

Single phase 3 wire was popular in areas previously served with 3 wire DC as the same mains could be used. There is STILL some in use !
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Old 28th Jun 2022, 12:09 pm   #64
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It is now very hard to find space heaters or clothes dryers with a full 3 kw loading. I suspect that this is due to a de facto admission that cheap modern 13 amp plugs and sockets are not able to reliably handle a continual 13 amp load.
To be fair I doubt it. That would suggest that producers are considering the UK market separately from others. They won't be.
I disagree, many parts of Europe have 10 amp power circuits, and other countries have 10 amp socket outlets on 16 amp circuits. So the demand for appliances limited to 10 amps is very substantial.
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Old 28th Jun 2022, 12:11 pm   #65
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Default Re: Tin Foil - makes you weep

[QUOTE=broadgage;1480926]
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Single phase 3 wire was popular in areas previously served with 3 wire DC as the same mains could be used. There is STILL some in use !
I have seen what was originally a 250-0-250V DC supply cable (tramway associated) supplying two phases of a three-phase supply. I don't know how having a single neutral which was the same size as the phase conductors was reconciled.

PMM
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Old 28th Jun 2022, 1:56 pm   #66
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Single phase 3 wire was popular in areas previously served with 3 wire DC as the same mains could be used. There is STILL some in use !
I have seen what was originally a 250-0-250V DC supply cable (tramway associated) supplying two phases of a three-phase supply. I don't know how having a single neutral which was the same size as the phase conductors was reconciled.

PMM
Presuming that the supply system was of the standard 3 phase, 4 wire type, but with only two phases and the neutral being utilised via an existing 3 core cable, then the neutral current wont exceed the phase currents. So no problem if the cable had a FULL SIZED neutral.

If however the existing cable had a reduced neutral, as most DC mains did, then that could be a problem.

Many existing 3 wire DC mains with a reduced neutral were reused for AC supply but this was best done with single phase 3 wire AC on which a half size or smaller neutral is fine. Some remain in use today.
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Old 28th Jun 2022, 3:43 pm   #67
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I wonder if double-pole fusing was used to facilitate testing of individual circuits? I have a late Victorian GEC catalogue that includes house wiring diagrams, where the light switch was in the L conductor and the fuse in the N conductor. Removing the fuse and turning the switch to the OFF position allowed the circuit to be tested without disturbing any wiring. Regular testing seemed to be more of a thing when electrical installations were in their infancy, and as the installations of the day were 110V or lower, a blown fuse that left a lampholder live would not have been considered hazardous.

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Old 28th Jun 2022, 5:21 pm   #68
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I wonder if double-pole fusing was used to facilitate testing of individual circuits? I have a late Victorian GEC catalogue that includes house wiring diagrams, where the light switch was in the L conductor and the fuse in the N conductor. Removing the fuse and turning the switch to the OFF position allowed the circuit to be tested without disturbing any wiring. Regular testing seemed to be more of a thing when electrical installations were in their infancy, and as the installations of the day were 110V or lower, a blown fuse that left a lampholder live would not have been considered hazardous.
In my first house, it had obviously been wired for electric lighting, was before any socket outlets. Most of that infrastructure was still in place as is, though new faceplates in place of the old switches. The original main switch and fuses for that circuit were still in place. Switches and fuses in both sides of the circuit. The switches were actually single switches with a bit of wood joining the toggles. I'm sure it was something that could be bought like that, the piece of wood was nicely turned. The fuseholders were round ceramic with screw on lids, that took fuse wire. At least someone had the sense to increase the rating in the N holder at some point.

AFAIK the supply in the town was initially DC so it all kind of makes sense.
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Old 28th Jun 2022, 7:53 pm   #69
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Default Re: Tin Foil - makes you weep

In Sunderland in the 30's the corporation electricity enterprise cabled up the streets with a 3 phase+N supply fed from distribution pillars. This was at 240v/ 440v and may in those days have been 40Hz
They ran a scheme called "hired wiring" whereby you paid for the work on your quarterly electricity bill as part of the standing charge. This covered the installation of service cut out, meter and 2, double pole switchfuses neatly mounted on a varnished ply board fixed to the wall with pot insulators.
One switchfuse (5A) was for lights (main rooms only) and the other for a single 5A, 3 pins socket outlet, run on 7/029 and fused at 15A (so room for expansion).
These were new installations but still used DP fusing

Ed
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Old 28th Jun 2022, 9:32 pm   #70
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Default Re: Tin Foil - makes you weep

Those paired switches with wood links were a standard GEC product: - extract from the 1912 GEC catalogue attached.

Also the house wiring plan from the 1893 GEC catalogue. It does actually say that the switch may be in either conductor. The catalogue also has a plan for warehouse lighting that has double-pole fusing but I haven't scanned that.
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Old 29th Jun 2022, 8:15 am   #71
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Default Re: Tin Foil - makes you weep

The 1893 wiring of a "private house or mansion" was interesting on a number of levels. Apart from the fact that it is astonishingly early for electricity installation (late Victorian) it shows the WC right next to everything to do with food preparation and storage

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Old 29th Jun 2022, 8:49 am   #72
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Those paired switches with wood links were a standard GEC product: - extract from the 1912 GEC catalogue attached.

Also the house wiring plan from the 1893 GEC catalogue. It does actually say that the switch may be in either conductor. The catalogue also has a plan for warehouse lighting that has double-pole fusing but I haven't scanned that.
The particular one isn't shown, but is described by item S457.
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Old 29th Jun 2022, 12:13 pm   #73
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990The catalogue introduction refers to GEC's 10 years' experience working with contractors and manufacturers. It includes lots of equipment for small-scale private electricity generation as well as large plant for central generation. Lots of choices for local power for driving your dynamo: water turbines, oil engines, gas engines and steam engines. Only DC dynamos with battery storage, apart from an AC generator for experimental and laboratory use. 1893 was the year Swan's light bulb patent expired. The catalogue shows both Swan's lamps and GEC's own brand lamps (Stella) that they were then only selling abroad, and which would become available in the UK after Swan's patent expired, and looks forward to the construction of what would become the "Robertson" lamp factory at Hammersmith . A range of domestic and light industrial electrical appliances was available: - kettles, frying pans, toasters, irons, glue pots etc.

Last edited by emeritus; 29th Jun 2022 at 12:21 pm. Reason: Mention of the Robertson factory added
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Old 30th Jun 2022, 3:43 pm   #74
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Default Re: Tin Foil - makes you weep

One of my colleagues from a while ago served his electrician's apprenticeship down a pit. He claimed that on one memorable shift they had a task to disconnect something from a junction box. The foreman asked 'What do we do first, Michael?' To which Michael brightly replied 'We isolate the junction box!'. Having done that, to his own satisfaction, and opened the junction box, the next question was 'What do we do now?'.

'Well, we unscrew the terminals on here'.

'No!' was the reply, and the foreman threw a three-pound hammer into the box. There was a huge explosion, and all the lights in the pit went off.

Much later, once the lighting had been sorted out, they could see the hammer head welded across the terminals, and no sign of the wooden handle at all. This was, of course, because they had gone into the wrong junction box.

There's a lesson in there somewhere.
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Old 30th Jun 2022, 3:49 pm   #75
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There's a lesson in there somewhere.
Never assume. It makes an ass out of u and me.

Trouble is you need a few near misses like that one to develop the self-preservation skills, or you have to be trained properly so that they become part of your backbone. That is what seperates amateurs from professionals, IMO.
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