Comments on: Or you could just wait 'til there's smoke

by: richardw66

Tue, 14 Jul 2009 01:18:05 +0100

I used to have one of those socket testers myself - handy gadget.

I believe it's just a neon from Active to Earth and from Active to Neutral for the OK lights.

A neon between Earth and Neutral for the not OK.

There's nothing more dangerous than discovering you are working on a switched neutral system when you think you are working on switched active. I once blew a Miele washing machine controller once by making this mistake, very, very expensive.

I have also seen someone nearly get fried whilst working on an external hard drive case that was switching the neutral line, thereby rendering the whole circuit live when switched off.

I also got caught out myself when fixing a ceiling light fitting after turning off the switch, but the circuit was active due to some rather old wiring.

Polarisation is important!!! Even when you believe that sensible people would stay away from the active.

Not all residents of houses are electrically certified, and insulation will not always be fully intact for the life of the device.

by: Red October

Tue, 09 Jun 2009 16:39:58 +0100

Cloth insulated K&T wiring can last quite well indeed, if it is not overloaded. As it passes through the air it can easily dissipate heat and doesn't need to be as thick as other types of wiring. No insulation should be installed around it, which can complicate insulation of upgraded construction, as the plaster-and-lath walls of the day were quite insulating of their own, but the modern wallboard types are less so, and often unknowing homeowners install insulation over the stuff and result in overheating. In the US, for refference, it is ostensibly legal to perform your own wiring work.

The worst such job I saw was all in a house that has since been plowed under. Old, perhaps the 30s, construction, upgrade in the 40s to finish the attic. The upgrade drew the power for the upstairs entirely from the kitchen lighting drop, so if that fuse blew the entire upstairs, the kitchen, and several other areas were plunged into darkness (The code of the day stated that no one room could be fed by a single circuit, so that a failure would not plunge an area into total darkness). The kitchen was on the way to the cellar where the fuse box resided. Some well-meaning idiot had installed "tamper-proof fuse adaptors"; little threaded tubes that allowed only a certain type of fuse to be installed (all our regular fuses use an Edison base), ostensibly preventing over-fusing but also preventing installation of the very useful mini circuit breakers.

by: Mohonri

Wed, 03 Jun 2009 01:58:20 +0100

@n17ikh - One of my coworkers lives in a 1930's house, and just had all the knob-and-tube wiring redone (at considerable expense). That is indeed some very intimidating stuff, but he brought a few pieces for show-and-tell, and I was impressed with how well the insulation has held up.

by: magetoo

Sat, 30 May 2009 21:46:09 +0100

It's an unusual socket, at least in my experience, that is not polarized. Some exceptions are the sockets on overhead lamp fitings [...]

And here in Sweden, all sockets and plugs are non-polarized. Except those that are involved in lighting. (round, often completely symmetrical, three-prong - some trial and error is often needed) It is my impression that all of proper Europe uses Schuko and Euro plugs now. That's one vote against rarity of unpolarized sockets I suppose... And I'll second the need for a preview function.

by: Red October

Fri, 29 May 2009 16:32:02 +0100

The "Lamps need to be polarized because of the Edison Screw base" argument is one I've heard before but still can't come to tearms with. The metal part shouldn't stick out of the socket at all. Such a socket is faulty. There should always be a paper insulator. Once the bulb is screwed partway out, the circuit is broken even if the fitting in question is energized. Only a cirtifiable idiot puts his digits into a possibly-energized electrical fitting of any sort.

About the most unsettling fitting I have is a light socket that is quite simple in its construction; a single piece of porcelain with flanges to put screws through, and the two terminals exposed to the world on the sides. This fitting was removed from service in the late 1990s! I've seen some pretty scary stuff done by the homeowner, but nothing so bad simply in its own existance as that. The same house had a mix of Greenfield cable (Otherwise known as BX armoured conduit/cable -it has a spiral armour jacket that serves as an earth) and very early NM (nonmetalic) cable that had a sticky black coating and, IIRC, no earth at all. Through some miracle, however, every actual receptacle had earth available (I tested them all; didn't bother with the lights). One final thing of note; very many heavy appliances like ranges and dryers get a 240V split phase system with only three pins; two hots and a common return which also serves to earth the circuit! This is contrary to all other practice in this country.

by: frasera

Fri, 29 May 2009 16:30:24 +0100

yea basically i've never seen a 2 prong only us socket ever in my life. i know they exist in very very old homes perhaps, but i've never seen one personally. i've used the plug wiring verifying doohicky when replacing my house recepticals with the prettier designer or whatever more angular looking ones. the only place where plugs are varied is the 240 appliance connections, there are plugs of different types or simply a wiring box, because well, appliances tend to be installed by installers so it doesn't matter.

by: n17ikh

Fri, 29 May 2009 15:10:05 +0100

@Red October: There is actually a good reason for lamps to use a polarized plug (in the US at least). We use Edison screw connectors, so there's a great big surface inside (the female screw thread part) that catches errant fingers and sometimes almost sticks out a small bit from the insulating surface surrounding it. It's a bit safer to have the hot side connected to the relatively small connector at the bottom of the socket instead of the big screw thread at the edge of it. If we used bayonet connectors, it wouldn't matter so much. Also, if you folks think cloth wiring is scary, you should check out knob and tube wiring, which is pretty frightening. However, as anyone who collects antique electrical appliances knows, there are some pretty dodgy things around. My mom has (and uses!) a toaster that has a nice chrome-and-stainless-steel chassis and horizontally-strung nichrome wire under a clever basket to toast the bread. You flip the bread manually, and it's a neat toaster, but the nichrome wire is of course bare and sometimes falls off the porcelain posts it's strung around to contact the surface of the toaster (which, by the way, is wired to the wall with a nice cloth and India-rubber plugset), leaving only a tiny set of bakelite handles on the bread-basket between the user and a nice shock. Of course, when it was manufactured, there was no real electric code. It probably was plugged into one of the aforementioned porcelain light-fixture sockets. Also: Dan, your comments system needs some sort of preview button. This tiny little window is no place to write up a comment of any real length.

by: Hobie-wan

Fri, 29 May 2009 14:42:30 +0100

My previous living arrangements (I'm in the US) were in some old converted slaves quarters that were pretty ancient. None of the plugs were grounded and the entire electrical system in the place was scary. As I recall there were only 2 or 3 old circuit breakers in a very rusty and weather worn box outside for the entire 2 bedroom apartment. The wiring inside the walls, aside from being ungrounded, was old rotting cloth insulated *cough* wire, and I swear I saw some aluminum when putting a ceiling fan in my room.

No wanting my PC to be unprotected in the unfortunate time I was living there, I took it upon myself to at least ground my PC. I bought one of those horrible 3 to 2 adapter jobbies with the tab, then ran some (house wiring spec) wire from the tab out the window to an earth stake I found in the bushes. The 'ground ok' light on my power strip came on, so I assumed it was all right.

Man I was afraid of dying in a fire in that place.

by: Red October

Fri, 29 May 2009 10:17:00 +0100

As a child I collected old electrical fittings. In houses built as far back as the 20s polarized sockets were common. Most everything else was not polarized, extension leads, most actual appliances, etc. Most of the sockets were of the "T-slot" type and could supply 120 or 240 volts (rated 120VAC, 15A, 240VAC, 10A). It's an unusual socket, at least in my experience, that is not polarized. Some exceptions are the sockets on overhead lamp fitings (Something that may shock those living abroad is that in the US it is very common for a procelain overhead light fitting to have an integral electric socket, probably relics of the days when light sockets were the only common power points in a home and these would be seen as upgrades. Early variants are unreliably polarized; modern variants are earthed and still sold today, and even installed in new construction, usually in places like basements where conventional outlets are uncommon.) and the integral plugs on things like bathroom light fixtures (to facilitate the connection of electric shavers, blow dryers, etc, as even when plug sockets became commonplace, they were not in the bathroom until the 60s or 70s) and stoves. There is an annoying trend here for things that don't need to be polarized (lamps, for instance, double-insulated electric appliances, etc.) to have polarized plugs for no good reason, making old octopus taps, extension cords, etc, hard to use. Another device that may unsettle the rest of the world are the ground cheaters; devices that austensibly allow a 3-pin grounded plug to go into an ungrounded receptacle, typically having a pigtail or flange to allow it to connect to the plate screw (which must be earthed but sometimes is not). When earthing began to be recognized as useful, some interesting experiments were made, including using a plug type identical to the Australian plug! Many houses have earthed receptacles in the kitchen but not elsewhere.

by: Alex Whiteside

Fri, 29 May 2009 03:08:12 +0100

On the subject of mains electricity, and deceptiveness... Looks like it would work in the UK (it has HK plugs which are compliant with BS-1363 I believe, and it's the right kind of GSM).