Lighting Wiring

[BigWallop]

That's the bit that get me as well.

[ARWadsworth]

I am sure it would work. However, the junction box needs 6 terminals not 5 and you can easily connect a three gang switch plus strapper cables into a

25mm back box as all but the earth connections are into the lightswitch.

-- Adam

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[Mike Tomlinson]

In article , Gertzy writes

It's very simple if we take the ASCII diagram Andy Wade posted, with the intermediate switch removed for simplicity and a couple of alterations:

L1 L1 O===========blue=============O=========== 'Live' \ red wire C O=============red================O C \ O===========yellow===========O=========== Switch return L2 L2 black wire/red sleeve (switched 'live')

Hall Landing Landing switch switch ceiling rose

Now tilt your head to the right so you're looking at the diagram from "top to bottom".

You'll see that the wiring is much simplified over the schematic you suggested. All that is needed is twin core and earth from the landing ceiling rose to the landing switch (i.e. the same as all other lights with single-way switching), and then a short run of three core and earth between the landing and hall switches. The number of wire connections is also minimised - all connections can be made to the back of the switches.

This way of doing it also has the advantage that it's easy to convert any single-way installation to two-way simply by running a length of three-core+earth from the first switch to an additional switch.

Your suggested wiring diagram at , while it would work, would mean running a length of twin+earth from the ceiling rose to each switch, PLUS another length of twin+earth between the switches.

[Shaun Robertson]

ARWadsworth wrote

LOL I hadn't noticed that it was marked "5 terminal junction box" but actually had 6!!

Thanks for your help Adam.

[Andy Wade]

That's historical: in the days when houses were wired with singles in conduit the 'original method', if I can call it that, was used. The alternative method was then only used when converting from one-way switching to two-way.

The original method is still used for conduit wiring where, with correct layout, large current loops can be avoided.

[Dave Plowman]

I'd add that the way you've called it a ceiling rose or junction box would confuse a newbie as you've laid out the terminals in a way they wouldn't come across. A ceiling rose often confuses the first time, so I'd have shown the terminal layout as it actually exists. And a junction box with the more usual 4 square layout.

You've got to decide what you're aiming for - either a theoretical wiring diagram as Andy supplied, or a practical layout.

[PoP]

Just a guess but you could probably do this with a clamp meter on the live feed to the lighting circuit. Switch all the lights on to see what the load is then multiply by 240 to get the wattage.

I bought a clamp meter on ebay for about 15 quid several days ago. It might not be particularly high quality but it's purpose for me was to give general indications rather than accurate readings.

Alternatively, if you aren't into techy solutions, wander round and add up the wattages for each of the light bulbs. That has the advantages that (a) you don't need a clamp meter and (b) you save electricity by not having to turn the lights on.

PoP

[usenet]

... but the overheating and so on is almost certainly caused by using

100 watt bulbs in sockets designed for a maximum of 60 watts and not to do with the circuit being overloaded. Overloading of the circuit as a whole would likely only affect the fitting nearest to the CU and/or the wiring between it and the CU.

[Dave Plowman]

Every bulb I've ever seen has the wattage marked on it. Add them all together and divide by 4 to give the amps - near enough.

[stefek.zaba]

Dave's keyboard caused the above to slip out into the ethersphere; but what was in Dave's head was to *multiply* by 4 and divide by a thousand. Thus, 1200W pulls 4800/1000 = 4.8A ...

Stefek

[Dave Plowman]

I've written out a thousand times 'mustn't post before the coffee kicks in'..