Old Christmas Tree lights

I've been asked to look at some old Christmas tree lights.
I am confident this will be the of the direct mains type with single insulated twisted pair and probably conforming to BS 4647:1970.
I am aware new mains lights of this type would have additional insulation as per BS EN 60335.
Obviously I can only do a visual inspection on them, but what is the current thinking of single insulated mains cable in terms of PAT or equivalent testing?
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When this has been discussed before, it has been stated that a double layer of insulation is required, ie a sheath within a sheath. How this is better than a single sheath of twice the thickness escapes me, especially if they are both the same grade of PVC.
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Graham.

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On 07/01/17 13:52, Graham. wrote:

If the outer sheath is damaged, the crack does not penetrate to the inner insulation. That's the job of the sheath - mechanical protection (of a lightweight nature) for the inner insulation.
It is NOT insulation in it's own right, though it usually is made of the same material and has similar properties to the actual insulation.
Case in point: Old T+E had lead sheathed cables. This of course was not an insulator :)
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wrote:

If you take a piece of PVC insulated cable and, with a knife, make a small cut in the insulation (not all the way through) and then bend the wire the cut will propagate around the cable leaving the conductor exposed. If you do the same with double sheathed cable the cut will spread around the outer insulation but not the inner. Double sheathing minimises the risk of surface damage to the cable exposing the conductor.
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wrote:

Presumably the idea is that a crack wont propagate thru the whole thing with a double layer of insulation.
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They are probably a Class 0 appliance. They are illegal to sell (even second-hand or in a car boot sale). If they have a similar age BS1363 13A plug, it will not have sleeved L&N pins, and that also makes it illegal to sell (even second-hand).
There's no hard and fast rule for the PAT testing - it will depend why they are being tested (e.g. would be a fail if being done prior to selling). Most commercial organisations and rental property PAT tests would also fail them. However, there's no law requiring they are failed - it's a matter of risk assessment. Given you can buy a new set at the moment for probably less than a quid, it's hard to argue there's any reason to continuing using such an outdated class 0 appliance. Also, LED lights are probably much safer on tress, and there are about 2 house fires a year caused by Christmas trees igniting.
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Andrew Gabriel
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On 07/01/17 13:27, Fredxxx wrote:

They would be noted as "Class 0".
The safest course of action would be to fail them as it's not really a big problem to replace with a modern set.
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On 07/01/2017 13:27, Fredxxx wrote:

Do it properly - this is after all uk.d-i-y.
Have a look at them in 352 days:-)
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In theory they are of course unsafe if a child unscrews a bulb, but in practice, I have had no problems with them as long as you always fit a fuse bulb and that the place where they go into the holders are well sealed.
Brian
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On Sat, 7 Jan 2017 18:10:48 -0000, "Brian Gaff"
Or worse, a child used to dabbling with wires and stripping them with their teeth, puts both ends of the broken light loop in their mouth.
And of course they were still plugged in and turned on ... ;-(
It threw me back across the room but I did live to learn a valuable lesson. ;-)
Cheers, T i m
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I had a similar experience with a neighbours door bell transformer at the age of 11 or 12. I assumed the bell wire I was attempting to strip with my teeth was connected to the secondary side. It wasn't.
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Graham.

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On 07/01/2017 21:18, Graham. wrote:

I had a similar exerience with a flashgun charger, at about the same age, and the "low voltage" was (IIRC, it was a long time ago) achieved with nothing more than a dropper resistor. A lesson learned...
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On Wed, 11 Jan 2017 15:16:01 +0000, Chris Bartram wrote:

And me with an old 18 set, one of these:
http://www.wftw.nl/wireless18.html
I was trying to see if I could isolate a failed audio stage in the transmitter by tapping a wet finger on each grid cap in turn to get a 'click' transmitted.
It went OK until I reached the PA valve, which had an anode cap ...
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On 07/01/17 18:10, Brian Gaff wrote:

I suppose an RCD or even a small 1:1 isolation transformer could be added to improve safety, if these absolutely have to remain in use.
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On 07/01/2017 13:27, Fredxxx wrote:

Many thanks for the posts. I did find a quote from the IET forum:
************************************************** The Code of Practice for the In-Service Inspection and Testing of Electrical Equipment (3rd Edition) has the following interesting note on Page 61:
"An example of Class 0 equipment is certain older styles mains powered series-connected Christmas tree lights where the lights are interconnected by a bell type flex type cable (insulated but not sheathed)"
If the equipment has been manufactured to BS 4647:1970, it could now be approaching 20 years old, assuming they were manufactured in 1989 as a credible best case.
In view of they type of equipment under consideration and the relatively small amount of capital it represents, the best course of action would appear to remove the equipment from service. **************************************************
The lady in question would likely err on the side of caution. If they are the type I suspect I will suggest she disposes of them. I don't believe they are too sentimental to hang on to.
Many thanks again for all the replies.
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replying to Fredxxx, Mark wrote: I just bought 4 packs of 80s tree lights from eBay a guy has tons of brand new box's he found in a warehouse totally new, I got them because they are the same design as most people here in the UK had back then had no idea about the situation that they are illegal to sell they are 4647 ones too. I am going to just use them for my little fake tree at Christmas, so I could still use them? As noone will be going near them to split the wires and the tree is on a table
I presume the safety issue would be if the wire were split.
BUT I was wondering I have seen rubber long flexible tubing that would easily go around the lights cables and it's alot thicker so would this also be a solution for someone who wanted to use the lights to stop any damage?
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On Thursday, 10 August 2017 16:14:07 UTC+1, Mark wrote:

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The downside is that the mains voltage flex is single insulated not double, so more easily damaged than modern mains ones (which could expose a live w ire). If you're concerned about mitigating this slight risk factor you coul d plug it into an RCD. Or if your house is one of the 50% or so with RCDed socket circuits the lights will be fine, even if not to the latest standard .
NT
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but don't do what a friend of mine did, put the RCD after a time switch.
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from KT24 in Surrey, England

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OOer. Many questions. Therese are filament bulbs then in series with a fuse bulb? The snag, ignoring the double insulation etc, is that they tend to blow short and eventually blow the fuse bulb. Nothing to stop you putting in a normal bulb and then if you are really careless, leave them on you could start a fire if the wrong fuse was in use. What I actually did was to put two pairs in series. Dimmer yes, but hardly ever likely to blow a bulb. also you still had the challenge of finding the loose bulb every year by laying them on the floor and twisting each one. Great task for a wet weekend. :-)
Mind you I'd imagine you time might be better spent accessing Usenet properly rather than through this home shower club nonsense. Brian
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Never had this problem in years of using such lights. They have *always* blown open circuit - in fact that his how my little light tester works.

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bert

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