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?

On Sat, 7 Jan 2017 13:27:27 +0000, Fredxxx wrote:

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?

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.




--

Graham.

%Profound_observation%

In article ,
Fredxxx writes:
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?

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argue there's any reason to continuing using such an outdated class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.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 07/01/17 13:27, Fredxxx wrote:
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?

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.

On 07/01/17 13:52, Graham. wrote:
On Sat, 7 Jan 2017 13:27:27 +0000, Fredxxx wrote:

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?

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.





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

On 07/01/2017 13:27, Fredxxx wrote:
I've been asked to look at some old Christmas tree lights.


Do it properly - this is after all uk.d-i-y.

Have a look at them in 352 days:-)


--
Adam

On Sat, 07 Jan 2017 13:52:41 +0000, Graham.
wrote:

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.

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.

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

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Fredxxx" wrote in message
news
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?

"Graham." wrote in message
...
On Sat, 7 Jan 2017 13:27:27 +0000, Fredxxx wrote:

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?

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.

Presumably the idea is that a crack wont propagate
thru the whole thing with a double layer of insulation.

On Sat, 7 Jan 2017 18:10:48 -0000, "Brian Gaff"
wrote:

In theory they are of course unsafe if a child unscrews a bulb,

snip

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

On Sat, 07 Jan 2017 19:34:42 +0000, T i m wrote:

On Sat, 7 Jan 2017 18:10:48 -0000, "Brian Gaff"
wrote:

In theory they are of course unsafe if a child unscrews a bulb,

snip

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

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.




--

Graham.

%Profound_observation%

On 07/01/17 18:10, Brian Gaff wrote:
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.

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.

--
Adrian C

On 07/01/2017 21:18, Graham. wrote:
On Sat, 07 Jan 2017 19:34:42 +0000, T i m wrote:

On Sat, 7 Jan 2017 18:10:48 -0000, "Brian Gaff"
wrote:

In theory they are of course unsafe if a child unscrews a bulb,

snip

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

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.




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...

On Wed, 11 Jan 2017 15:16:01 +0000, Chris Bartram wrote:

On 07/01/2017 21:18, Graham. wrote:
On Sat, 07 Jan 2017 19:34:42 +0000, T i m wrote:

On Sat, 7 Jan 2017 18:10:48 -0000, "Brian Gaff"
wrote:

In theory they are of course unsafe if a child unscrews a bulb,

snip

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

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.




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...

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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