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Topic Title: Safe method of transferring 230V power to a hinged attic trap door?
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Created On: 13 March 2019 12:41 am
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 13 March 2019 12:41 am
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urmia

Posts: 27
Joined: 07 August 2017

Hi guys.

Wondering if there's any safe and permitted way to get 230V power to a down light mounted in an attic trap door?

There's various solutions about, but they all seem to be relevant only to 24v and bringing power on to a door to operate say an electric lock.....

It'd be possible to use a loop of SY Mulitflex armoured flex cable, and even to put it inside a length of plastic trunking - but it'd need to fail safely. Also to be good practice in terms of the regs.

A trap like this isn't going to open very often, but better not to take any chances...

Thanks
 13 March 2019 01:10 am
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mapj1

Posts: 12039
Joined: 22 July 2004

we had a thread asking this very thing about 6 months ago
seemed to conclude that a bit of flex in a position where it would not get snagged was enough.

edit, that thread was from you in fact.

-------------------------
regards Mike
 13 March 2019 01:09 pm
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AJJewsbury

Posts: 17795
Joined: 13 August 2003

SY probably doesn't provide much of an advantage over ordinary flex - the steel braid makes it less flexible and as the braid isn't rated for use as a c.p.c. it can't be relied on to initiate ADS if the flex becomes damaged.

In your other thread you mentioned "the door is insulated, so the light will be more or less buried in it" - that could be an issue. Burying lights in insulation is a bad idea as all lights produce heat and that heat needs to dissipate. LEDs might not produce enough heat to start a fire, but being semiconductors they're very sensitive to temperature and can fail after a very short time if allowed to overheat. Just cutting away the insulation around the light can lead to problems with cold spots and condensation. Under normal loft insulation the usual procedure is to create a relatively large void around the light with the loft insulation running above/around that, but that's probably not practical on a moving hatch.

- Andy.
 13 March 2019 01:16 pm
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daveparry1

Posts: 8020
Joined: 04 July 2007

I'd have thought ordinary sheathed flex would be ok for that, leave a small loop at the hinged edge of course.
 13 March 2019 02:51 pm
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dustydazzler

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 14 March 2019 04:10 pm
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urmia

Posts: 27
Joined: 07 August 2017

Sorry mapj1, guys - the curly flex was the most solid option that seemed to come up then, but I couldn't seem to source it then from our wholesalers or on the web.

Still a tiny bit wary of the idea too. Those found on offer just now quote an electrical flex standard, but make no mention of any standard to do with how much bending they will tolerate.

That said I ran another search just now, and found some suppliers on Amazon UK offering 0.5m before extension lengths in 3 x 1.25mm2 rated for 230V - so I've ordered it.

It's a flex (multicore) cable in spiral form - so I guess it ought to last well/fail safely. I'll try to find a position for it that minimises the bending, and isn't likely to contact somebody should it somehow fail...
 17 March 2019 09:18 am
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Dave69

Posts: 789
Joined: 16 July 2011

Originally posted by: urmia

Hi guys.



Wondering if there's any safe and permitted way to get 230V power to a down light mounted in an attic trap door?


- but it'd need to fail safely. Also to be good practice in terms of the regs.





Thanks


Hmmm the fact you say it will need to fail safely seems to suggest you have no confidence which in turn suggests the solution is not suitable.

If the trap door is hinged its not really an issue but if the trap door is free the problem will be it will simply be pushed up and thrown out of the way leaving only the cable to stop it flying across the loft, not good for the cable or the light fitting.

Trap doors are not that big and surely it is basically a very poor design if you need to fit a down light in the trap door in the first place.
 17 March 2019 09:56 am
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potential

Posts: 1774
Joined: 01 February 2007

Place a 13a socket near the trapdoor and use this flex.
240V 13A COILED CABLE MAINS FLEX
Use a suitable fuse in the plug.
 17 March 2019 10:50 am
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ebee

Posts: 6735
Joined: 02 December 2004

Begs the question, is there no way arouind putting a light on the trapdoor?

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 17 March 2019 02:26 pm
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urmia

Posts: 27
Joined: 07 August 2017

Thanks guys. The cable is ordered, but to fill in some more details.

The trap door is hinged, part of the otherwise identical manual version of the powered attic stair system here: https://www.skylarkstairs.com/ It's a standard hinge, so the door is fully located. It opens to about 45 deg.

It'd be much less hassle to place the downlight (Collingwood Halers H2 550 LED - very low power) elsewhere, but the retro fitted trap (which for practical/visual reasons had to be where it is) eliminated a fixed downlight and takes up pretty much all of the ceiling area in a short and not so well lit corridor exiting the kitchen.

ie it would be possible to install a wall mounted light over the door or somewhere, but it'd look badly out of place.

The insulation won't be a problem, it's rigid PIR board, and is deep enough to accommodate the light in a hole sawed opening which will let it breathe freely. It'll be placed tight up under a step so that it's well away from anybody's foot, with a protective perforated steel cover over it - there's a zinc plated roofing bracket available which fits the bill nicely.

My caution about using the spiral cable followed from the fact that the standards I saw quoted by sellers apply to normal flex - there's no mention as before of how much bending it can tolerate. That said the stuff is sold for trailing leads to hot plates and the like, so it's probably fine. The one I've ordered is as in your link P.

I guess it's a scenario not covered in the IEE guide...

The fused plug and socket is a good idea too, thanks...
 17 March 2019 07:10 pm
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Jaymack

Posts: 5571
Joined: 07 April 2004

I'd be looking at a wall mounted light.

Regards

Edited: 17 March 2019 at 07:16 pm by Jaymack
 17 March 2019 10:58 pm
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urmia

Posts: 27
Joined: 07 August 2017

Hi J. It's definitely the safe option.

The big question I guess is what happens in 20 years or whenever - when the insulation has hardened etc. When somebody who no awareness that it's a live cable climbs the stairs...
 18 March 2019 09:43 am
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ectophile

Posts: 857
Joined: 17 September 2001

Originally posted by: urmia

Hi J. It's definitely the safe option.



The big question I guess is what happens in 20 years or whenever - when the insulation has hardened etc. When somebody who no awareness that it's a live cable climbs the stairs...


I have an old vacuum cleaner in the loft that I was using up to a couple of years ago. It still has the old red/black/green cores in the flex, so it was probably last replaced in the 1960's. That flex has been rolled up and unrolled countless times, dragged around the floor, and been run over by the vacuum cleaner many times.

Yet it is still completely intact.

I wouldn't be worried by a bit of flex on a loft hatch. The environment is harmless by comparison.

-------------------------
S P Barker BSc PhD IEng MIET
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