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Lamp Wiring
| About Underwriters Laboratory |
UL is concerned with safety. They do not want fires. They do not want a single person to suffer an electrical shock. They surely do not want anyone to be hurt, let alone die from electrical equipment. They are not really interested in quality. So choose your parts for quality, and never, never, knowingly purchase any part that is not listed by UL.
UL has an inspection program to list assemblers of lamps (manufacturers). It is not free. In fact it is very expensive for small outfits such as you and me. Thus, using listed lamp parts is not enuf. The parts must be used properly, and the lamps inspected regularly.
My personal policy is to assemble my lamps as close to UL standards as I am able. I feel I am just as interested in protecting my customers from danger as they are.
One thing UL is adamant about is maintaining polarity. About thirty years ago, they began requiring plugs with one blade wider than the other. From a practical standpoint this means that the wide blade must always be connected to the ground side in every attachment. To help you, the ground wire always has lines embossed in the plastic insulation. Every socket has silvery (nickel, aluminum or tin) colored ground connections, and brass colored hot connections. If you have more than one bulb in a lamp, make a special effort to maintain polarity between the bulbs. Another help: The button in the center of the socket is always the hot; the shell with threads for the light bulb is always the ground.
Another thing UL enforces is protecting the cord from exiting the lamp. For if the cord is pulled right out of the lamp, it can spark and start a fire. It does not happen very often, but I had one customer who could have been hurt, had he not been able to call the fire department right away. He hired me to inspect every lamp in his house, and repair the dangerous ones.
 Tying knots keeps cords from exiting lamps. One popular way is to construct your lamp body with a hole in its side. Then you merely knot the cord just inside the lamp. Sometimes you cannot do that, so an alternative technique is available. Tie an Underwriters' knot within the light bulb socket. The knot is illustrated in figure one. At your request, I will send you a real cord with the special knot tied properly. You don't even have to buy a lampshade. Recently, socket manufacturers have been making the sockets a little bigger, to more easily accommodate the knots.
Based on my experiences, plus input from knowledgeable persons, I've developed a policy for choosing cords and sockets. Cords are the easy classification. They are all good, and all appear to be equal. Brown is my favorite color because most backgrounds are brownish. Also, it rarely shows dirt and grime. Gold, it seems to me, is too gaudy for a handmade lamp. In addition, both gold and silver corrode over time. Sockets are the tough classification. There are no good ones, only bad and badder. Even tho they are rated for safety at 300 watts, all of them fail in a year or so when used with 200 or 250 watt bulbs. Years ago, they operated well under those loads. I think, but cannot prove, that they've reduced the amount of copper in the internal wiring. As a policy, I only use the type with screw down studs. The type with little knife blades might fail to make good contact. And I routinely advise customers to use 150 watt maximum bulbs. Those who require brighter bulbs because of vision problems must expect to replace sockets often.
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