Dimmer switch wiring fire risk - "Controlled Test"

[John Webb]

Found at:
http://www.bbc.co.uk/news/science-environment-13312076

I am lost for words.........

[ahmedh]

Mental note "avoid powered and exposed dimmer switches left in a bin full of cotton wool."
I shall store that in by brain next to the mental note "switch my mobile phone off when filling my car with petrol" 

[Wiz]

I think it is right that such serious fire risks are highlighted by the media. Let's face it, every day all over the country, there are hundreds of over-driven dimmer switches laying about in waste paper bins with cotton wool soaked in fire accelerant

That such incidents makes 'good TV' for those with very little understanding of fire risks, is neither here nor there.

[nearlythere]

Not as big an everyday risk as a wicker basket full of solvent saturated cotton wool as it would be if someone started to throw lit matches into it only to be exacerbated if there was also a leaking gas cylinder in the bottom of the basket and .....................................
Look, it could happen. Right!

[Midland Retty]

Now now dont be too quick to mock lads!

Before bed Mrs Midlandfire perches herself at her dressing table applying make up remover with cotton wool, which inturn gets disgarded into a small bin. By the end of the week it is simply overflowing with cotton wool doused in make up remover.

The waste is probably very very flammable, and I will be removing all electrics from the bedroom as a precaution.

This does one of two things - it reduces the risk of fire occurring, and secondly the lack of lighting means I won't have to see her without any make-up on ! *shudder*

[wee brian]

If he had just set fire to the shed I would have enjoyed it just as much - the pretence of some kind of engineering just spoiled it.

[SamFIRT]

Personally I think you are all missing the point.  It shows the principle that heat is generated in supply circuits by the use of switched circuitry dimmer switches.
You are taking it all too literally. Perhaps because it is a TV personality and is light-hearted in it production?

Let’s remove the acetone soaked cotton wool and replace it with combustibles in a loft space with the supply circuits covered in loft insulation to prevent heat dissipation? Add in a poor connection allowing a high resistance fault to establish and a thereby creating little bit of carbon build up leading to a carbon tracking fault. Or perhaps the heated wiring being run through timber with insufficient air space left and therefore creating repeated charring effects thereby setting up a smoulder condition exacerbated by albedo heat absorption effect in the roof sub structure.

Not seen any of those conditions?

Judge not lest you be judged. 

[Wiz]

Personally I think you are all missing the point.  It shows the principle that heat is generated in supply circuits by the use of switched circuitry dimmer switches.
You are taking it all too literally. Perhaps because it is a TV personality and is light-hearted in it production?

Let’s remove the acetone soaked cotton wool and replace it with combustibles in a loft space with the supply circuits covered in loft insulation to prevent heat dissipation? Add in a poor connection allowing a high resistance fault to establish and a thereby creating little bit of carbon build up leading to a carbon tracking fault. Or perhaps the heated wiring being run through timber with insufficient air space left and therefore creating repeated charring effects thereby setting up a smoulder condition exacerbated by albedo heat absorption effect in the roof sub structure.

Not seen any of those conditions?

Judge not lest you be judged. 

Yes, a TV programme showing more likely scenarios would have more of an impact on we cynics who are tired of shock-horror dramatics.

[John Webb]

Personally I think you are all missing the point.  It shows the principle that heat is generated in supply circuits by the use of switched circuitry dimmer switches.
You are taking it all too literally. Perhaps because it is a TV personality and is light-hearted in it production?

Let’s remove the acetone soaked cotton wool and replace it with combustibles in a loft space with the supply circuits covered in loft insulation to prevent heat dissipation? Add in a poor connection allowing a high resistance fault to establish and a thereby creating little bit of carbon build up leading to a carbon tracking fault. Or perhaps the heated wiring being run through timber with insufficient air space left and therefore creating repeated charring effects thereby setting up a smoulder condition exacerbated by albedo heat absorption effect in the roof sub structure.

Not seen any of those conditions?

Judge not lest you be judged. 

I don't disagree with you, but as someone who spent 28 years carrying out 'controlled fire tests' where we strove for realism and reproduction of what did actually occur in real fires, I found the content of the BBC programme featured in the link I posted to be laughable. As Wiz says, a more likely scenario would not only have had more of an impact on us who have some knowledge of the subject but might have more impact on the less knowledgeable viewer. It was a lost opportunity, in my opinion.

[SamFIRT]

a more likely scenario would not only have had more of an impact on us who have some knowledge of the subject but might have more impact on the less knowledgeable viewer. It was a lost opportunity, in my opinion.

Possibly

But it is meant to be entertainment with a little bit of subliminal education.

But I take your point, if it had been a documentary. 

[David Rooney]

All it proved was that when things get hot in the wrong circumstances it can start fires.

Hardly rocket science. I'm sure people at home will be very wary next time they throw their very hot dimmer switch in the recycle bin.

If they wanted to educate they should have shown the effect of loft insulation on extra low voltage lighting and associated circuits.......

[John Webb]

In fact the effect of the extra heating from dimmer harmonics on SELV wiring in insulation (particularly if the wire was damaged by kinking in installation) would have been a far more realistic scenario - not so dramatic but much more likely to happen in practice.

[SamFIRT]

(particularly if the wire was damaged by kinking in installation)

Why ? *interested*

[firstforensic]

Reminds me of that Fire Safety advert on the tele. The one where the man drops his lit cigarette on top of the duvet as he drops off to sleep and it immediately bursts in to flame! I suppose the moral is . . . in there somewhere.(well it is friday afternoon)

[John Webb]

(particularly if the wire was damaged by kinking in installation)

Why ? *interested*

I was on the fringe of work done at Fire Research where in the early 1980s there was a query about the damage that occured when wiring was being installed. It was found that if a Twin and Earth sheathed cable was kinked this could cause sufficient damage that the damaged part would overheat. When immersed in roof insulation the cable insulation could be sufficiently heated to be badly damaged, and if the roof insulation was a shredded paper fill in particular, this could be ignited. Hence my suggestion above.