Hacker News Reader

Comment by raldi | Hacker News Reader

> The UK has a unique way of wiring houses which doesn't lend itself well to automated control.

I never heard of this. Does anyone know what it refers to?

Edit: Free karma points for anyone who sketches ASCII art diagrams of the replies! The links are nice, but none of them show how switches and lightbulbs work in ring vs radial.

View on HN

Neutral is not usually present at the switch, which makes it hard to power things.

There is a lighting ring main through the lights, and each switch is a spur that gets "live" and "to lightbulb". Whereas it looks like other countries run power to the switches, and then to the light.

Edit for diagrams: http://www.howtowirealightswitch.com/2-way-switch-with-power... ("UK") versus http://www.howtowirealightswitch.com/2-way-switch-with-power... (neutral at switch, suitable for powering other electronics)

Okay, I think I get it. They're both electrically equivalent to this circuit:

    White main --- Bulb ----+
                            |
    Black main --- Switch --+

But "equivalent circuits" are not actually equivalent when you're an electrician. It makes a big practical difference whether the main goes to the bulb, with the switch as a spur (UK), or whether the main goes to the switch, with the bulb as a spur (US and others).

P.S. Everybody please give pjc50 the karma I promised.

That would be a ring circuit¹). It's also the reason why UK plugs²) tend to be fused.

¹) https://en.wikipedia.org/wiki/Ring_circuit

²) https://en.wikipedia.org/wiki/AC_power_plugs_and_sockets:_Br...

It might be referring to the "daisy chain" wiring, which means that every plug has the fuse inside the actual plug itself. This is why UK plugs are so huge. The reason for this is after WWII there was a copper shortage and it was cheaper to wire houses this way.

I believe the UK uses ring circuits: https://en.wikipedia.org/wiki/Ring_circuit

Reply on news.ycombinator.com