Advice on vintage metal lamps - rewiring - earthing

[mackered]

Hi,

I've been using two of these lamps (2&3) for quite some time with a simple two to three pin converter but having purchased the latest (1) I started to question whether they were safe, being two pin vintage lamps from Europe, and mostly metal - as far as I know not earthed!

If they do require earthing then I would like to rewire them with suitable 3 core flex and a three-pin UK plug, guessing a 3amp fuse would be the one to go for.

1. Is a strip lamp design, all metal and I'm certain all metal parts are in constant contact with each other. It currently has the original 2-pin plug and flex with a push button switch (mid cable). The two wires go into the connector
and just below I have noticed a little brass screw - could I run the earth from a 3-core to this with a suitable tab connected?

[img]http://i.**********/SdC0YH9.jpg?1[/img]

[img]http://i.**********/c8lGu8C.jpg?1[/img]

2. This is all metal, metal lamp holder too. 2-pin original flex with an original push button switch which I would like to keep. It looks to me that all metal parts are in constant connection but how would I go about earthing this one? change the lamp holder or earth inside it and or earth to one of the screws inside the metal housing? Will a 3-core flex work fine with the original push button switch?

[img]http://i.**********/DCvPw0r.jpg[/img]

[img]http://i.**********/lZ1SIy5.jpg[/img]


3. This is an all metal floor lamp, completely original with 2-pin plug, the cable runs throughout the whole stem, pops out the top and go through a brass (with some kind of shim between) pivot which the head rotates on, then into the lamp head and into a bakelite or plastic lamp holder. Same applies, do I need to earth and if so how? Or is the plastic lamp holder ok to retain and just stick with an adapter.

[img]http://i.**********/PKPoqat.jpg[/img]

[img]http://i.**********/BJYkSfL.jpg[/img]

[img]http://i.**********/GeiZAqN.jpg[/img]

The first 2 look like I may be able to do them myself, with a little advice, the 3rd probably looks like I need to pass it onto a professional if it does need earthing. Any help appreciated.

[Dave Moll]

I'm sure opinions will differ, but for my own part I like to know that my metal lamps are earthed via three-core flex in case internal flex insulation becomes worn, bringing a live conductor in contact with the casing. Sometimes, the difficulty can be finding three-core flex thin enough to pass through the channels designed for two-core.

I had this latter problem with a vintage toaster that would be considerably less safe unearthed with its live heating elements in close proximity to the metal casing, but I was unable to thread the (braided) flex through the cable retainer. At least with a lamp, PVC flex can safely be used, and is usually available in smaller diameters than braided flex.

[mackered]

That's a good point Dave, I'll check the width of the current wiring. Thanks for the reply.

I was hoping for a simple white 3-core flex for one and black for the other, keeping them close to the original design. The floor lamp may be tricky as it has to thread through the entire design.

[Ed_Dinning]

Hi, make sure the plug has a suitably low rated fuse fitted for additional protection, especially if you need to use low current rated cable to fit in the lamp.
3A fuses are easily available 1A and 2A can also be found.

Ed

[McMurdo]

the first two just need 3 core mains flexes and earthing as you assume, the last one being articulated might be difficult to earth throughout as an articulated joint would not be considered a reliable continuous conductor, so I would thread a double insulated cable through the arms and use a double insulated lamp holder with integral cable clamp. You might need to change the switch unless you can get the earth continuously through the switch body. That original figure-8 cable might be made with 'toughened' insulation which in some countries is considered 'equivalent' to european double insulation, but I wouldnt trust it myself.

[mackered]

I opened the switch on the 2nd all metal lamp, looks to me as if the metal lamp holder is earthed so I should be able to pop a 3 pin low amp on.

http://**********/LUq9poG

[The Philpott]

Yes mackered, then with it unplugged (of course) check continuity between the 'earth' pin of the plug and the metal parts of the appliance and the lamp holder. You are looking for a very low resistance, indicating that should there be a problem in future, current tends to flow through the earth circuit you have made, rather then through yourgoodself. A low budget multimeter (with instruction manual) will do this test very well.

Also this lets you check for infinitely high resistance between the metal 'chassis' and the lampholder pins or sockets that contact the terminals on the bulb/lamp.

This is what we like- people making things safe rather than deeming them obsolete and chucking them in the skip.

Fuses of 1 or 2 amp can be found quite easily, as mentioned.

[Okto1984]

I have sometimes used 1 amp fuses for table lamps. They're more than enough for a 60w bulb - but they always seem to blow when the bulb fails. Occasionally they have also blown when turning on the lamp - usually when they've been in use some time. Since all my lamps have 0.75mm cable, 3 amp fuses are fine, they're well below the cable's rated amps.

In general, I've found 1 amp fuses very prone to failing - despite the appliances having no faults, and being well below their amp rating.

[emeritus]

The 1A fuses probably blow because they blow faster than the plain wire internal fuse that GLS lamps have generally been fitted with in recent times. Previously better-quality GLS lamps were fitted with fast-acting Ballotini fuses consisting of a fine fuse wire in a glass tube surrounded by tiny glass balls (Ballotini) that quenched the arc, but latterly Osram Philips and GE only fitted plain fuse wire. I used to get my bulbs from Woolworths, who were possibly the last supplier of Ballotini-fitted GLS bulbs, and I used to use their lamps with 1A fuses with no problems. When I used other makes, the 1A fuse used to blow when the lamp failed, almost doubling the cost of lamp replacement, so I had to fit 3A or 5A fuses.

See #36 of this thread:

http://www.vintage-radio.net/forum/s...=133621&page=2

for photos.

Some of the presently-available allegedly "rough service" tungsten GLS lamps seem to be fitted with this sort of relatively slow acting fuse that can cause modern circuit breakers to trip when they fail, although they can give satisfactory service with older fuse wire-fitted consumer units.

[The Philpott]

I do use one or two rough service bulbs, but the lumens per watt rating is quite poor and the spectrum is a little further towards the red end than 'conventional' filament bulbs. You do need to buy a reputable make if going down this route. There was some scaremongering over their use in domestic premises 'invalidating household insurance policies' which is only really worth looking up if you need a good laugh.

[broadgage]

Returning to earthing, or not of vintage lamps, IMHO it is increasingly worthwhile to leave vintage lighting equipment "as is", presuming that it works of course.
Fit a modern 12 volt lamp and use a plug in transformer or PSU.

No need for any earth with only 12 or 24 volts. The choice of lamps is very good these days and includes incandescent "bus bulbs", compact fluorescents and LEDs.

I recently restored to safe working order a vintage wrought iron room divider or decorative screen about 6 feet high and 8 feet wide. This consisted of about a dozen SBC lamp holders mounted on and between decorative wrought iron scroll work, together with holders for small pot plants, the better that water may drip into the bulb holders!

I replaced all the wiring and bulb holders but would still not be happy about mains operation, So I fitted a 25 volt transformer and used vehicle lamps.
As an added refinement I used twin filament 5/21 watt bulbs and fitted a switch to select either 5 watts per lamp/about 60 watts total, or 21 watts per lamp/about 250 watts total.

[The Philpott]

That's a cunning way of approaching it, although if using automotive filaments i would under-volt them by at least 5% to offset the short life expectancy.

[matthewhouse]

Aren't auto bulbs designed for 14/28V already? I would expect the life to be good at 12/24V.

[The Philpott]

They do have a wide voltage tolerance to account for the alternator voltage, yes, but the expected life is, in some cases at least, one tenth of what we hope to get from an average GLS 240v filament.

[broadgage]

I can not agree that vehicle lamps have a short life.
They are optimised for about 13.5 volts for "12 volt" lamps and about 27.5 volts for "24 volt" lamps. 14 volts or 28 volts at the battery and about half a volt drop in the internal wiring.

They often last years of regular use and have been known to outlast the vehicle.

When under run at an actual 12 volts the life is still greater, and the absence of prolonged or severe vibration also increases life.

Vehicle lamps tend to be reasonably efficient, often better than low wattage mains voltage lamps. The shorter and thicker filament tends to give either a greater efficiency or a longer life than the long and fine filament of a low wattage mains lamp.

They are also very cheap, I have seen packs of ten for £3 on line.

[Herald1360]

Given that modifying anything opens a right can of worms liability wise, I'd be inclined just to replace the original flex with sheathed two core and fit an RCD plug.

Of course the low voltage option would be fine as long as the transformer / PSU itself is suitably safety certified, but it may be rather more hassle!

Of course the low voltage option would be fine as long as the transformer / PSU itself is suitably safety certified, but it may be rather more hassle!

Plenty available off the shelf.

[AC/HL]

One off topic post removed.

[The Philpott]

I largely based the premise for automotive bulbs having a shorter life-span on the average life of the 'stop' filament of a 'stop and tail' which is, believe it or no, 100hrs. (Wordenweber, Wallaschek, Boyce & Hoffman, 2007) Dropping the voltage will help, but it isn't a cure.

Contrast this with even a bog standard 240v GLS at 1,000hrs...... The only reason your brake light filaments may last years is that you don't drive with your foot on the brake all the time- not unless you're wearing clown shoes, at least.

A single filament 21w indicator/reverse/rear fog won't be much better, probably related to the high wattage in a small envelope. The same applies to the miniature 5w units with an envelope about the size and shape of a index finger tip; they simply don't have the hours.

I wasn't referring to halogens as the recombinant phenomenon of the filament tends to extend life, provided the minimum voltage for recombination to occur is reached.

The earlier idea someone mentioned of using 12 or 24v- 21/5w twin filament bulbs as a dim or bright facility for an old luminaire of limited safety standards is sound, but only if you can live with the 100hr life of the 21w. The 5w one will actually be pretty good at an average of 1500hrs, again, understandable as a low wattage in a largeish envelope.

All these bulbs will by design have a wide voltage tolerance while staying within their design life, as has been hinted at before.

[emeritus]

Interesting comment on the design life of automotive bulbs. I remembered I had an old, very comprehensive, catalogue from a small lamps distributor, and on digging it out, I found that the only types of lamp for which no life is stated, are automotive lamps! As an aside, when replacing a blown turn indicator lamp in my Vauxhall Astra, I noticed that, in each rear lamp cluster, instead of the expected two 12V 5W sidelight lamps, I found two 12V 21W lamps connected in series. Each gives out about the same light as a 5W lamp, and I suppose being operated at half voltage, they should last pretty much indefinitely.