SHEDNOTES 4 – The secrets of Earth

Once upon a time, life was simpler, but more dangerous.
It looked like a simple job for The Shed to fix up a couple of old table or bedside lamps which an uncle made for my parents as a Christmas present nearly 60 years ago, from spindles of oak turned into a barley twist pattern. I think they came out of the banisters of a house we lived in, with grandparents and some lodgers, which was eventually condemned.
The lampholders worked loose and the flexes became brittle and brown many years ago but I kept the remains, intending to do my bit for the family heritage.
When I eventually got round to it, I discovered there were only two wires in the flex – no Earth, in other words. The uncle who put the lamps together was pretty handy and nobody died when they were in daily use, so I was tempted to simply follow his example. But one of the old lampholders – the bit the bulb slots into – was made of brass and the plastic insulation on the other one was a bit chipped, so I thought it was probably my job to introduce a new Health & Safety precaution, in the form of a wire to take the current safely away to Earth if something goes wrong.
There appeared to be no ready-made connection for an Earth on either of the bulbholders. I chucked away the tatty plastic-coated one, which probably dated back to a repair my dad did, and looked closely at the plain brass one, which probably dated back to the original handy uncle.
It had a couple of flat brass pillars which held the on-off switch in place and there were screws from them into the switch. I supposed I could catch an earth wire under one of those screws, or solder it to one of the pillars. But would that mean the Earth only worked if the switch was pushed to that same side? I wasn’t sure.
I tried to dream the circuitry of the switch and how it would fit in with the lampholder going accidentally live but had to give up. I passed an old-fashioned hardware shop and splashed out on a new brass lampholder and, reluctantly, some new three-core flex. Normally it is a rule of The Shed that broken things are patched up from other broken things, but one of the casualties of the move from Cellar to Shed was the loss of my important collection of cables and plugs for all occasions.
I did keep some nice old-style silk-wrapped flex but it was only two-core and twisting another strand into it made it too fat for the lamps. We were going to have to make do with plastic again.
Still, at least the new cable included an obvious Earth wire and the new lampholder had an obvious place to screw it in.
Now, if I expected all the wire ends to stay in place for another 50 years, I decided, it was time to have another go with solder, to give the screws something substantial to grip on. Soldering is one of those arts I have spent decades failing to master. My only comfort is that most people are the same. I remember talking to a professor of electronics who told me the first thing he did with his students was to set them to work producing three-dimensional cubes with wire and solder. Only when they could do that were they ready to move on to theory.
I stripped back insulation, leaving just enough bare wire to work with, and cut the earth wire a little short at the lampholder end and a little long at the plug end, so it would reach its terminals without being folded too much. Then, for good luck, I doubled over the ends of bare wire and soldered the folded wire together into a good lump. Ready to roll. I headed back to The Shed with a cigar unwrapped and ready to light. I guessed I could finish off the first lamp in the time it took to smoke it.
But I had made several mistakes. First, the soldered ends of wire were too thick for the holes they had to go into, and when I tried to trim them by snipping and filing, I ended up with the loose strands of wire I was trying to avoid in the first place. Second, I had prepared for the final connections by threading the cable through the base of the lamp and then up through the spindle to the hollow bolt which the lampholder would screw onto. I tried a temporary assembly and discovered that it was impossible to screw the lampholder down tight because the flex needed to turn with it. I took it all apart, to start again, and it was a good job I did. Another mistake had been to remove the outer insulation of the cable using a pen-knife to score around it until I could break it loose. When I looked closely, there were little cuts in the insulation of the core wires, where I had cut too deep. Next time round, I peeled back the outer insulation before using a wire stripper to bare the ends of the core wires. And this time, instead of trying to make good connections by twisting the wire, I fanned the strands slightly and then lightly tinned them with the solder, to make a sort of spade end. Finally, I left the flex hanging loose until the lampholder was wired up and screwed down tight.
There was no indication on the lampholder that it mattered which way round the brown and blue wires were connected. I assumed the modern health and safety industry would have insisted on giving me a clue if it made much difference.
The assembly all came together quite neatly. Just in time, I remembered to take the lampholder off again and make sure the wires were not only screwed in, but tucked around the little plastic pegs designed to hold them in place if the flex got tugged.
It all seemed fine. But what was the safe way to check?
I plugged the lamp into the mains and tried switching it on without touching it. Nothing happened. I switched off at the mains, pushed the switch on the lampholder across and switched on at the plug again, without touching the lamp. Bingo. But sooner or later, I had to try moving the switch on the lamp while the plug was live. First, with the bulb lit, I touched a light-up circuit tester to the outer brass of the lampholder, with my thumb on the top of the handle. Nothing lit up, which was good. Finally, wearing flip-flops, I switched the light on and off using the switch incorporated in the lampholder.
All seems fine. But I am wondering if there is any more I can do before I give the thing to anybody else to use. No shop would take any small electrical appliance, nowadays, without a certificate to say it has been declared safe by a qualified person. To pay for a test would be both a disproportionate expense and an offence against the rules of The Shed. But the least I can do for my family, it seems to me, is to at least attempt to duplicate the kind of inspection the law requires. What would an electrician do? I Google for DIY electrical safety tests without finding the answer.
The lamp goes back into The Shed while I call for help.
I joined for occasional help with crosswords but the site can sometimes summon impressive firepower on technical questions.
I started off with
1) If there is no place for the earth connection on a brass lampholder, could I solder the earth wire to any place on the body of it?
2) The lampholder includes two brass pillars which hold the switch in place. Could I attach the earth to one of those or might that mean it was ineffective if the switch was off?
Best answer was from The Builder, who said:
“Any metal-bodied fitting must be earthed, and have a 3-core cable (2-cores are for ‘double insulated’ fittings which don’t need an earth.
I wouldn’t earth with the switch pillars for the very reason you mentioned. Solder to the lampholder by all means. A mechanical connection by drilling and self-tapping screw would also be fine.”

My next question was:
3) If there is no indication on the lampholder where to connect live and neutral wires, does it matter which way round they go, taking the switch into account?
The Builder said: “Not important with conventional bayonet fittings. Only matters with Edison Screw bulbs where, the live should connect to the pointy bit of the bulb, and the neutral to the screw bit.”
But another correspondent, Heathfield, said: “While the lamp will still work whichever way round the wires are connected, the preference would be for the brown (live) wire to be connected to the cable’s plug side of the switch. That way, with the switch in the ‘off’ position, you wouldn’t get a shock if you stuck your fingers into the lampholder.”
I wasn’t sure what he meant but mention it here for further research later.
Finally, I asked
4) Once the job is done, is there any DIY version of the legally required safety tests for small electrical appliances?
Heathfield said: “Not really. Electricians have to pay a lot for PAT testers, which aren’t aimed at the DIY market.”
And nobody else was keen to encourage me to try. So the next step, I think, is to find a shop to do a Portable Appliance Test, just to see how much it costs and what it tells me. More on this later.

Meanwhile, for the Filofacts collection:
Jeff Howell in Teleg 2010 on SEALANTS …
“Silicone is tougher, harder, shinier and ideal for around baths, showers and basins. Acrylic sealant stays softer after cutting, shrinks more upon drying, but can be painted over. Acrylic is therefore better as a frame sealant around external doors and windows.”

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