Wiring problem

Hello, I'm trying to change some light switches for PIW switches so they come on when my disabled brother walks into the room.
My problem is that the PIW switches require a live in, a live out and a neutral and light switches in the UK only have a live in and a neutral.
Can I connect the live out to the neutral as well as the neutral to the neutral as shown inn my diagram here:
http://www.flickr.com/photos/49057290@N05/8267477718/in/photostream
The crossed out line is what don't have and want to replace with the dashed line. Being as the switch controller is drawing such a low current will this make any difference to the outcome? Will they now be in series rather than parallel and would this matter?
Thank you
David
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Obviously one drawback would be that the bulb would be live at all times, but would that matter? Would it only have 0.2W passing through the filament when the switch was off?
D
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On 12/12/2012 11:12 AM, David B wrote:

The unit should work if wired they way it was before you crossed out stuff. The 'live out' is the output from the device.
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Yes, that's how it should be wired. The problem is I can't wire it like this without a lot of rewiring between the light and the switch. Will it still work the way I've drawn it (even though there will be a constant low current going through the bulb?
D
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On 12/12/2012 11:31 AM, David B wrote:

You are not supplying neutral to the device the way you drew it.
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I am, through the filament of the bulb, so it would be like having a 0.25A fuse in line which should make no difference to the device.
D
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On 12/12/2012 11:43 AM, David B wrote:

The bulb filament would act like a resistor and the device may not function properly. AND, do you wish to violate all your electrical codes?
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What you've drawn will not work. Once the contact for the live in/out wires close, you will be cutting out power to the PIW device. This will cause the contacts to again open. This cycle will repeat and in turn giving you a blinking bulb effect.
With the style of wiring in your house, what you need is a PIW up at the light fixture. Once installed you would just keep the wall switch on all the time, except possibly when he's asleep.
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You can get a few light fittings with a PIR built in, although they're not particularly pretty looking (tend to be a plain circular dome), e.g. http://cpc.farnell.com/eterna/cf28pir/ceiling-light-with-pir-28w/dp/SR08250?Ntt=SR08250
Another option, if you can easily get to the wiring above the ceiling, and if the switch drop cable is in conduit or behind capping and can be used to draw a new cable through, is to replace the cable with triple-and-earth, so you can get a neutral supply to the switch point.
(And before anyone suggests it, no you can't use the earth as a neutral return in the twin-and-earth cable.)
--
Andrew Gabriel
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It happens that David B formulated :

Have you thought of the problem of the light going off again after he sits still for a short while?
--
John G



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On 12/13/2012 6:01 PM, John G wrote:

I hate when that happens in a public bathroom.
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Even worse if you're at home, it's dark, and you're standing up!
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On 14/12/2012 8:26 AM, JW wrote:

Memory! it's what we old people have to do when the hose and the aiming control are obscured by the belly-depend on aural feedback. If the hearing aid batteries have gone dead-sonar is also dead. Sit down to be sure.
--
Don Kelly
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On 12/12/2012 11:12 AM, David B wrote:

Hello, and this isn't rocket science. The motion detector (MD) electrical circuit should be connected to the AC power source which in your case would be live in (hot) and neutral so that the MD internal circuits are continuously energized. The live out goes to the controlled device (lamp). I can certainly understand why you might have a light switch in a box without a neutral but I would avoid trying to kluge something together. It would probably be in violation of your UK electrical codes. Sincerely,
--
J. B. Wood e-mail: arl snipped-for-privacy@hotmail.com

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