Table lamp electrical advice please

[Peter907]

I've made a small wooden table lamp, and would like some advice on wiring it to a 3 pin 240v plug in accordance with UK regulations.
My problem is, that with "normal table lamp" 0.75mm squared 2 core cable, the cable tends to be rather stiff when used with my very lightweight 10" tall table lamp. This lack of flexibility will easily cause the lamp to fall over. The lamp has an E14 bulb holder with just a 2 watt LED bulb. Obviously for such low wattage, 0.75 mm squared cable is substantial overkill, but my googling so far seems to be suggesting that I need to use this size cable as a minimum.
Legally, can I use thinner more flexible cable for this lamp, or do regulations require I use a minimum of 0.75mm squared? If so, I will need to fit some sort of lead weight into the base to help balance it.
Thanks in advance.

 

[Dibs-h]

I've made a small wooden table lamp, and would like some advice on wiring it to a 3 pin 240v plug in accordance with UK regulations.
My problem is, that with "normal table lamp" 0.75mm squared 2 core cable, the cable tends to be rather stiff when used with my very lightweight 10" tall table lamp. This lack of flexibility will easily cause the lamp to fall over. The lamp has an E14 bulb holder with just a 2 watt LED bulb. Obviously for such low wattage, 0.75 mm squared cable is substantial overkill, but my googling so far seems to be suggesting that I need to use this size cable as a minimum.
Legally, can I use thinner more flexible cable for this lamp, or do regulations require I use a minimum of 0.75mm squared? If so, I will need to fit some sort of lead weight into the base to help balance it.
Thanks in advance.

Can you have the cable running from the bulb holder to the base (attached firmly\loosely somehow) and then from the base to the socket? Even have the switch in\on the base?

 

[Peter907]

The cable exits the table lamp in the centre of the underside of the base, which is 105mm square and 20mm thick.

Yes, I could fit a small switch on the base, however, any movement the 0.75mm squared cable will still move the lightweight lamp around and possibly knock it over.

I would be interested to know the regulations on minimum cable size for a 2 watt bulb in this situation, but will if necessary, modify the base with weights to stabilise it. Would prefer to wire it with thinner flexible cable so such modifications are not needed.

 

[Spectric]

Legally, can I use thinner more flexible cable for this lamp, or do regulations require I use a minimum of 0.75mm squared?

There are no laws regarding what you do, the regulations are also not legally binding and only offer " best advice / guidance" but would be used against you if you were to cause injury through your work in any court proceedings, they are a two edged sword.

You can use any size cable you like providing it is protected by the correct fuse rating in the plug, can carry the current required by the load and complies with the maximum allowed voltage drop of 3% for lighting. I would suggest 0.5mm cable and a three amp fuse in the plug.

A bigger question regards the protection, is there any metal conductive components such as the bulb holder, if so then you need three core to provide a CPC to earth the lamp, if it is a plastic bulb holder and no metal components then two core providing the circuit it is pluged into has RCD protection.

 

[Peter907]

Thanks @Spectric

I think 0.5mm cable would be much more flexible and better for this small lamp.

Is an RCD really necessary? Here's a pic of the bulb holder and bulb, the only metal is in the two screw connectors and the bulb thread in the E14 plastic holder. All the other parts are wood. See pics....

 

[Sideways]

I would try to add weight into the base whatever you do. Lightweight lamps that fall over annoy me.

 

[Spectric]

Is an RCD really necessary?

I think you have not understood this bit, what I said was " providing the circuit it is pluged into has RCD protection." in other words the socket has RCD protection which will be in your consumer unit, it should have at least one RCD or more likely a split board with two. All domestic properties should have the extra protection of an RCD but always worth mentioning because you find odd cases of circuits wired without. I would say that you can use two core and no CPC is needed because there is no metal parts.

 

[Peter907]

Thanks for clarifying @Spectric

I understand now. The lamp will be used in a newish property with an up to date consumer unit. I had in mind the old RCD plug-through units that could be bought at garden centres for use with electric lawn mowers and other outdoor power tools.

Thanks @Sideways

Might as well do it right, from the start. I will use 0.5 mm squared cable and weight the base.

 

[graduate_owner]

I seem to remember in the 1966 (ish) IEEE wiring regulations it became necessary to use twin and earth cable to all light fittings, wheras previously an eart connection was not needed. The reason is householders might fit lampshades with exposed metal, which then needs earthing. Things have changed somewhat and the introduction of RCDs might mean this is no longer necessary, but worth checking up on - since you want to do it right.

K

 

[Spectric]

All changed since 1966, residual current devices have made things a lot safer providing they are periodically tested by the home owner. In theory if you stick a finger in a light bulb fitting then the RCD will disconnect, PLEASE DO NOT DO THIS AT HOME to verify. Back in the sixties we had electric irons with a two pin light fitting bayonet.

 

[ajs]

You'll be fine with 0.5mm² cable for any reasonable length of flex, indeed it is often sold as "3A cable".

As for protective earth the question for me would be simply is there anything to earth? An Edison screw fitting you have the screw and the tip both carrying current, the holder is plastic sheathed and that's your lot. No metal frame to attach to... where would you fit an earth? Bayonet fittings can be slightly different since the metal shell is isolated and the clip can profitably be earthed, but not the case here. Connect the screw to neutral, tip to live - it's marginally safer that way but appliances should (by law) be minimally safe even if live and neutral are reversed.

You'll generally find round cable is better behaved than oval, and although it is stiffer, three core is often preferable to two even if the third is unused. Two core naturally defines an axis around which the cable will naturally prefer to bend. Round three core cable doesn't so will do as it is told.

 

[Valhalla]

no CPC is needed because there is no metal parts.

What about the lamp holder?

 

[ajs]

What about the lamp holder?

See above, for Edison screw you have the screw and the end contact. Both carry current so are inappropriate to earth. It's also why you never see exposed metal shells on the holders as you do sometimes for bayonet fittings - as I pointed out above the screw is ideally neutral but the safety implications of it being live must be considered.

 

[flying haggis]

could you fit a taller shroud round the lampholder to shield the exposed metal of the bulb, even a bit of 32mm drain pipe might suffice

 

[Spectric]

Any exposed part of the bulb is not relevant providing that it is neutral and not live, the centre terminal of the holder should be live. As I previously said,

In theory if you stick a finger in a light bulb fitting then the RCD will disconnect

but how many people check there RCD's periodically using the "test" button and then how many actually have had them tested with the relevant tester to ensure the tripping times are within spec.

I have had RCD's that have failed full test but tripped using the test button and others just failed so just having RCD's does not guarantee electrical safety, they are just another layer of protection when functioning correctly.