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Topic Title: Dodgy Class II Table Lamp?
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Created On: 28 December 2009 07:06 PM
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 28 December 2009 07:06 PM
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tenbob

Posts: 2
Joined: 25 July 2008

Hi All.

I recently bought a new table lamp from a large DIY chain. It looks nice, but I'm not at all happy with its safety. I wonder if more experienced members could comment.

It's a modern variant of the Anglepoise with a mains voltage halogen bulb in the head. It's labelled as Class II and has a 2 core mains flex. The lamp is made of stainless steel tube, with three knuckle joints along its length and a swivel joint where it attaches to the base. The mains wiring goes up inside the tubes and through the various joints to reach the bulb.

The wiring inside the metal tubes is not well protected against mechanical damage. There are two separate wires having what looks like standard thickness PVC insulation. At the points where it passes through the knuckle joints, the two wires are over-sleeved with some woven sleeving.

What is worse is the swivel joint at the base. At this point there is no oversleeving and the basic insulation is in direct contact with a metal bush. As you swivel the lamp the insulation of the wires rubs against this metal bush.

The underside of the lamp's base is covered by a flimsy sheet of self adhesive plastic reinforced with corrugated cardboard. It is easy to peel this off by hand to reveal the wiring. This is sleeved in heat-shrink tubing, so no live parts are directly exposed.

At the moment the insulation is sound, but I am very concerned about the long term performance. The insulation may become brittle and fail with continued rubbing or flexing at the joints. This is after all an adjustable lamp and is intended to be moved around repeatedly. Because the lamp is made entirely of metal you are bound to be in contact with it, if the insulation should fail.

What do others think? Personally, I'm not going to use it. But is it OK for this to be on the market at all? It does have a CE label.

Regards, Bob
 28 December 2009 11:34 PM
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betnwah

Posts: 236
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CE labels are self-certification. If the maker thinks his product complies with the applicable standards he can slap a CE label on it - no independent testing whatsoever is done.

If you feel that this product is unsafe please take it to Trading Standards.
 29 December 2009 02:57 AM
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andy01

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Joined: 27 December 2009

I think perhaps you might be confusing practical reality and certification.

I would suggest that you are evaluating this lamp on the basis of practical reality. I would do the same myself. I'm not suggesting that the certification is irrelevant, but "Luminaires" have different regulations to that of all other electrical equipment. I'm not exactly sure of the detail, but what I can remember stems from my work calibrating electrical safety testers, a while ago.

Strangely enough, the testers themselves didn't seem to come under any significant scrutiny or certification beyond a NAMAS reference. Given that they were implicitly Class I equipments, it was my duty to subject them to the extended practical test. In my opinion that is a more rigorous test than many certified equipments are ever likely to see.

My experience was that standard electrical safety testers would be calibrated accurately, and testers for Luminaires would be brought as close to accuracy as they could achieve, by design.

The full on test, from what I remember, is isolation L+N to E below 10mA leakage @1500V AC, a similar DC insulation test with lower leakage, and also earth bond test less than 0.1ohms @ 25A AC.

Now, the thing is, that many Luminaires would never meet that anyway. On top, is the idea lighting stuff is rarely earthed. The problem is that lamps are designed by interior designers, and rarely engineers. It's pretty tough to police the design of a lamp, especially when it was designed to look nice. That's why you bought it, and why also it might be unsafe.

To me the issue is that the metal lamp is marked class II. Although it's not very good, the actual safety of the lamp is no better than you could expect. As far as I'm concerned it's only class II if the box and controls are made wholly of insulating materials i.e. wood or plastic, and then that insulated wiring is used.

Anglepoise style lamps (with the flexible tube) have been like this forever. They have a limited safe lifespan. You can take the manufacturer to task for their seemingly erroneous label if you wish, but I doubt you'll get them to change the design, which is the actual important bit.

If you can, use one of those plastic in-line switches on the cable to the lamp. If you never touch the lamp, it'll not bite you. (That's if it doesn't catch fire from the heat!)

Edited: 29 December 2009 at 03:23 AM by andy01
 29 December 2009 10:56 AM
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deleted_1_Grizzly01

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Originally posted by: andy01
As far as I'm concerned it's only class II if the box and controls are made wholly of insulating materials i.e. wood or plastic, and then that insulated wiring is used.


BS 2754:1976 would beg to differ
 29 December 2009 03:17 PM
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intrinsic4225B

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Yes - Form F and Form G construction as defined in BS 2754:1976 is the subject of much confusion when met in practice by those who have been educated that Class II equipment must be of 'all insulated' construction.

Also the misuse of the term 'double insulated' for Class II equipment, when double insulation is but only one of the methods by which Class II construction can be achieved.
 30 December 2009 01:17 AM
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andy01

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Originally posted by: Grizzly01

Originally posted by: andy01

As far as I'm concerned it's only class II if the box and controls are made wholly of insulating materials i.e. wood or plastic, and then that insulated wiring is used.




BS 2754:1976 would beg to differ


Yep!

That's exactly what I mean. You don't need much of an idea to see dangers that a little label can easily hide.

My point is simply that things can be "a bit dodgy" even if the label says they're all-right.

Wouldn't it be a fine thing if you could do something about dodgy equipment design, rather than dodgyness bound up in the acceptablity of legislation, rules and regulation?

FWIW, I was taught that class II equipments should be double insulated. I think that might be why I used the phrase "as far as I'm concerned". In real terms I don't mind how it's made, I just want to know it's safe.

Failing all of the above, there's always the siren call of; (dons Scottish accent) "It's a potential deathtrap!"

To the uninitiated, that's BBC Watchdog.


Edited: 30 December 2009 at 01:30 AM by andy01
 30 December 2009 10:38 AM
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betnwah

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Originally posted by: andy01Anglepoise style lamps (with the flexible tube) have been like this forever. They have a limited safe lifespan. You can take the manufacturer to task for their seemingly erroneous label if you wish, but I doubt you'll get them to change the design, which is the actual important bit.

I don't see why they couldn't look exactly the same but be Class I which would make them safer should the internal cable get damaged, especially as these days there's a good chance that they'll be plugged into an RCD socket.
 30 December 2009 08:09 PM
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andy01

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I think it could be myself, but that is only my opinion.

From the perspective of the manufacturer, why rock the boat? For them it's always been all-right, they probably know that the ground is a bit soft, and after all there are plenty of other manufacturers of similar goods out there. Rock the boat, and you risk losing your lucrative distribution contract.

From the perspective of actual implementation, there are some things to think about. The big one is that 25A less than 0.1ohms earth bond. That's got to apply everywhere on the metal exterior. I'm not sure you can rely on that just through the mechanical joints of the mobile arm. Also the design may use insulating plastic bushes between the metal components.

Much better is a screwed down wire connection between those components that are geometrically mobile. Also elimination of any plastic bushes that separate components.

There is also the problem that the earth potential in many domestic settings is actually quite high. Having made the lamp class I is it now likely to give someone a shock in that circumstance? Equally will it give someone a shock if another device fails to earth somewhere else in the house?

I think my own view on this is that there is no reason why the lamp could not be made almost wholly from plastic. The shade is probably an exception from the perspective of heat, but this could easily be electrically insulated with a phenolic nut fixture.

To make the "mobile part" in plastic is not straightforward from the perspective of strength, but often clever structural design can appear quite elegant.

Another way would be to make the lamp low voltage. Use a 12V dichroic, and have an isolating/stepdown transformer in the base.

There are lots of ways, I'm sure, but in the end it comes down to cost, and what people are willing to pay.

Perhaps, better still would be an array of high efficiency LED's. This, to a large degree would take away the heat problem too.

Edited: 30 December 2009 at 08:18 PM by andy01
 05 January 2010 05:18 PM
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tenbob

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Thanks for your helpful comments to my original post. I'd like to focus on whether the lamp meets the current regulations rather than how it might be redesigned in an ideal world. I'm afraid I'm not familiar with the detail of BS 2754:1976 and other relevant documents. I understand that to achieve Class II status the device must have some sort of "reinforced" insulation.

In this case, it looks like the manufacturers have taken a length of standard mains flex, removed the outer sheath then poked it through the steel tube exposing it to kinking and sharp bends. This doesn't sound very reinforced to me. But what do I know? Can anyone say how this might be considered "reinforced"?

Since my original post I have examined a number of other adjustable table lamps which all seem superior to this one. My original 1960s Anglepoise is a properly earthed Class I design. Admittedly, the earth is connected only to the lower part of the flexible arm. This means the upper arm and shade may may not be adequately earthed. But I'm not complaining.

A number of lamps I checked were Class II. These all had, like the Anglepoise, a significant design difference. At each flexible joint the flex was looped around the outside, rather than passing through the middle, of the joint. This reduces the danger of damaging the insulation and means that any damage is readily visible.

An adjustable table lamp is, in my view, a very demanding application, since it is intended to be moved about repeatedly by hand. It is quite different from a ceiling or wall light that stays put and is rarely touched at all. In this case the outside is made entirely of polished metal giving a very low resistance to the body. It's quite easy to imagine a scenario where I might reach out to adjust the lamp with my left hand whilst touching something earthed like the case of my PC with the right. If the insulation had failed this would have very serious consequences.

I'd still appreciate a reply from someone who can say categorically whether the lamp conforms to current regulations.
 05 January 2010 08:10 PM
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intrinsic4225B

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Some knowledge of the content of BS 2754:1976 is useful when assessing the safety or otherwise of electrical equipment.

I don't have my copy to hand at the moment, but the following definitions of 'Class II equipment', 'double insulation' and 'reinforced insulation' are taken from the IEE Code of Practice for In-Service Inspection and Testing of Electrical Equipment, 3rd Edition

"Class II equipment. Equipment in which protection against electric shock does not rely on basic insulation only but in which additional safety precautions such as supplementary insulation are provided, there being no provision for the connection of exposed metalwork of the equipment to a protective conductor and no reliance upon precautions to be taken in the fixed wiring of the installation. Refer also to BS 2754."

"Double insulation. Insulation comprising both basic insulation and supplementary insulation."

"Reinforced insulation. Single insulation applied to live parts that provides a degree of protection against electric shock equivalent to double insulation under the conditions specified in the relevant standard. The term 'single insulation' does not imply the insulation has to be in one homogeneous piece. It may comprise several layers that cannot be tested singly as supplementary or basic insulation."

The IEE Code of Practice for In-Service Inspection and Testing of Electrical Equipment, 3rd Edition is a useful document which you may find instructive to study, in terms of understanding the construction classes.

You should be able to view a copy of BS 2754:1976 at your local public library - its not a very long standard, and is reasonably easy to digest!

If you also have a look through the back issues of Wiring Matters, issues relating to the testing of electrical equipment have been covered at various times in the past.

If you are concerned about the safety of the equipment which you have been sold, you could perhaps bring your concerns to the attention of your local Trading Standards office for their investigation and if necessary, action?
 16 February 2013 12:32 PM
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MartinR

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Hi, I have recently taken up making table lamps and cannibalise CE marked lamps for the parts.

I was a chartered Electrical Engineer an one time, though this has lapsed and have a foundation degree in Electrical And Electronic Engineering, 30 years experience in the Design, Testing and Approval of mail sorting machines and 8 years experience of Domestic Wiring, PAT testing and Periodic Inspections.

With regard to the comments about dodgy table lamps, please see below:

Many of the lamps that I cannibalise are Class 2, often with metal stems, but plastic lamp holders. Initially, I was suprised at this.

All of the lamps are fitted with twin core double insulated cable.

Where the cable is stripped back to single insulation, each core is usually, but not always, covered in a secondary layer of insulation. I mimic this when I rewire each lamp with heatshrink (not shrunken).

I profide strain relief at two or three places, by using super glue on the tails to grip the flex to the lampholder, where the cable enters the stem and where it exits the lamp body, all with superglue, CA.

I class most of my lamps as Class 2 and place a PAT passed sticker, dated and with the lamp serial number and 'Not to be used in Bathrooms/Shower rooms', the Class 2 symbol and my contact details.

I carry out a fucntional test (to make sure the switch is on) and then measure the IR at 500 V between Phase (live and Neutral) bonded together and to any exposed metalwork. No earth bonding test is carried out for obvious reasons.

I also complete tilt test at 10 Degrees (I read somewhere that the guideline is 6 Degrees, but can't find any reference to this).

All details are recorded on a spreadsheet.

I believe that this more than fulfils the requirements of BS 2754, especially in the insulation tests.

I too was initially concerned about none earthed metal on Class 2 items, but have done enought testing now to realise that it is quite common, usually in Pedestal Fans and Standard Lamps.

So, the dodgy class 2 lamp mentioned at the start of this thread is quite common and as long as the cable is double insulated both when it is not stripped and where it is stripped back and the lampholder and switch are plastic, I cannot see anything wrong with it.

One things I think that does break the BS are the Chritmas tree lights, the wire framed Reindeer/Santa etc., where a single insulated 240V bearing cable is used.

I did contact TS about these, but they didn't seem very interested!
 18 February 2013 07:46 AM
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Patnik

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I must say I'm rather glad not to have to safety test these lamps of yours MartinR as they sound like trouble. Heatshrink does not stand up to multiple flexing very well at all and tends to split after a while if bent back and forth at the same place, it is no way a good substitute for the pvc outer sheaf ('secondary insulation' if you like) mains flex usually has. If there is one certainty of super glue it is that it will fail, using as strain relief sounds like a bad idea.

Nik
 18 February 2013 07:55 AM
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ebee

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The question you gotta ask is "do you trust the manufacturer?".

"Do you feel lucky punk?"

My answer is often "NO"

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Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 18 February 2013 09:21 AM
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MartinR

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Hi Nik thanks for the reply.

The heatshrink is not subject to any flexing as it is only used just below the lamp holder where the outer sheath has been stripped back to maintain the double insulation, so there shouldn't be any problems there.

As for CA glue failing: I'd like to put that comment to one of my friends who in the 70s made his first 3 million quid importing it in big drums, bottling at 1000s of percent mark up and now hand builds aircraft from scratch using CA and other bonding glues!

The cords are all subected to a pull force of around 5 kg, this representing the most likely weight of a lamp suspended on the cord.

Thoughts?

Cheers

Martin
 18 February 2013 10:11 AM
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Patnik

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Originally posted by: MartinR

Hi Nik thanks for the reply.

The heatshrink is not subject to any flexing as it is only used just below the lamp holder where the outer sheath has been stripped back to maintain the double insulation, so there shouldn't be any problems there.

As for CA glue failing: I'd like to put that comment to one of my friends who in the 70s made his first 3 million quid importing it in big drums, bottling at 1000s of percent mark up and now hand builds aircraft from scratch using CA and other bonding glues!

The cords are all subected to a pull force of around 5 kg, this representing the most likely weight of a lamp suspended on the cord.

Thoughts?

Cheers

Martin

The thing to ask yourself is can you be sure these improvisations will stand up to regular use over a period of many years. I've seen quite enough split/slipped heatshrink on mains flex and broken superglue repairs to know they are a bad idea. I've got to say I'm amazed that you think superglue is suitable for strain relief, it's not about suspended weight, you need to be wiggling it back and forth a few hundred times to replicate long term strain on a portable appliance. Cyanoacrylate has a low shear strength making it particularly unsuitable for this sort of thing.

Why not just use lamp holders etc designed for the purpose with strain relief built-in that will clamp to the outer sheaf of 2-core mains flex?
 18 February 2013 10:24 AM
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MartinR

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I wouldn't call it an improvisation!

The flex cannot move as it is in a hole not much larger than the cable (oval or round or braided) and is surrounded by CA glue.

I'm sure if I wiggled the flex around a few hundred times, the conductors in the flex would fail before the CA!

Cyanoacrylate Glue-CA has great tensile (pull) strength, not shear (peeling) strength as you say.

99% of the Class 2 SES lampholders that I has seen don't have strain relief per se, it is achieved in the tube below the lamp holder or where the cable/flex/cord passes through the lamp body to the outside World.

I provide both!

I don't believe that BS 2754:1976 is descriptive, it is prescriptive in the provision of strain reflief.

The point about the heatshrink is that it can't slip or split as its not exposed, its in the lampholder.

Martin
 18 February 2013 03:32 PM
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Patnik

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You've lost me now Martin. Don't see why you feel the need to superglue the flex to the lamp holder if the flex is just passing through the lamp body, strain relief is only needed where the flex exits the appliance. Similarly why heatshrink over single insulation within the lampholder? I was picturing something like an angle-poise with flex exiting direct to the outside world from the lampholder, they usually have a plastic screw clamp to secure. Maybe I just don't understand what you're describing and am imagining something worse than the reality.

Nik
 19 February 2013 02:34 PM
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M.Joshi

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In many lamps and other electrical devices, you often see a loose knot in the cable or hot-melt glue to hold the cable in place. Does the CA glue not react with the cable sheath or give off fumes?

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M.I.E.T - Forfeited this due to The I.E.T's ridiculous membership rules!
 19 February 2013 04:54 PM
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daveparry1

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The loose knot just inside the appliance sounds a much better idea to me, after all strain relief is only needed where the cable exits the appliance. The CA glue won't be giving off fumes once it has cured MJ,

Dave.
 19 February 2013 05:33 PM
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MartinR

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Originally posted by: M.Joshi

In many lamps and other electrical devices, you often see a loose knot in the cable or hot-melt glue to hold the cable in place. Does the CA glue not react with the cable sheath or give off fumes?


Hot melt glue has the breaking strain of a Crunchie bar!

I haven't noticed and reaction with the sheath. Perhaps I ought to try sniffing it and end up with a lamp glued to my nose!

Now there's a test of cable restraint?
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