Lamp and Light Fixture Inspections: Is it Safe?

April 29, 2016

With all the Restoration, Repurpose and Reclamation programs on TV, its easy to get inspired to pick up an old fixture and bring it home. However, buying used fixtures/lamps that appear to be working correctly might still have hidden problems. I thought it might be a good idea to devote an article to inspecting a lamp/light fixture.  As with any of my projects, safety is number 1, and with any electrical appliance, lamp or light fixture, insuring it remains compliant with the  electric code and the original UL listing  is very important.

pre purchaseWe recently picked up the swag lamp pictured to the side. The picture is from the location we bought it. As you can see it was working. So why would I want to take it apart? Just to check it out!  So, I disassembled it to clean, inspect, repaint the metal surfaces and total rewire if required. As with most any hanging type fixture with the bulb below the socket, there is a natural tendency for the rising heat to make an impact on the above wiring. As expected, I found brittle and decayed wiring above the socket. After seeing the condition of the wiring  I wondered why the fixture was working at all! Overheated wiring is the sleeping giant of lamp and light problems.  Most wiring is rated at 105C (or 221F), and in most correct applications will be fine, however when a bulb wattage is greater than the lamp rating is used, the wiring will be the first component to suffer.  You may never know it until the wiring is disturbed. Once disturbed, the insulation can disintegrate and potentially cause the wires to touch each other. You know where the story bad wiregoes from here. Always follow the bulb ratings requirements as listed on the fixture.

Without knowing the history on a light fixture, it never hurts to confirm that it is in good working order before you use it. Here is my basic check list: 

  1. Physical Review of the Lamp: Is it relatively clean, does it appear to have been stored inside or outside? Fixtures left outside can rust as well as rodents can get to places unseen to chew on the plastic wire insulation.
  2. Manufactured or Custom: In general, lamps that were manufactured in mass generally were designed and built to a specification. Typically they use standard lamp parts and overall meet the design criteria necessary for long term use. Custom lamps can be made from most anything (bowling balls, table legs, vases, etc.). Good custom manufacturers follow the same criteria. On the other hand, I regularly run across lamps that were hand built, but failed to ensure proper safety for long term usage. Many of them I can fix, but for various reasons a bad design can cause premature failure, in turn, it may not be a good lamp. The two most important items with custom lamps is 1)quality of workmanship and 2) proper heat dissipation.
  3. good bad wire comparoWiring terminations: Most failed wiring is at the terminations. Frayed/broken wires, premature insulation failure, loose connection can all impact the safety and performance of the light. In this picture the bottom wire has decayed insulation and has turned black in color due to excessive heat. The one on top is in good condition.
  4. Polarity: In a simply lighting circuit there is a “line or hot” side and a “neutral”. Those terminations should be consistent from the plug to the socket to ensure the hot termination is in the base of the socket not the shell. This is tested with a VOM meter.
  5. Polarized Plug: Similar to #4. The larger prong on the plug goes in the larger hole in the wall socket, which is the neutral side, maintaining the polarity through the entire circuit. If it is a lamp and has a plug on the cord and it is not polarized, it is a good idea to change it out.
  6. Wiring Size: Not usually a problem with US manufactured lights, but most lamps/lights originally designed to work in a different country could have undersized wiring for use in the US. After determining the wire gauge, this can be addressed in multiple ways including, 1)rewiring the lamp or 2)simply lowering the wattage of the light bulb to be used.
  7. Bulb Sockets: Sockets show wear for various reasons, including the cardboard insulator and the metal contact surfaces. Regardless of the reason; noticeable wear in the socket should be resolved by replacing it.
  8. Grounding circuit: Lamps have polarized plugs, but light fixtures require a grounding circuit. This could be a green wire, or a small bare wire, or even a black wire with green tape that is attached to the body of the light fixture. With a VOM meter, continuity between the conductor and the bare metal surface of the fixture can be confirmed.
  9. Switches: Most switches tell you when they are bad and there is little indication they are going bad; not a lot of  in-between. They can be good today, and bad tomorrow. If you have taken the lamp apart, changing the switch/socket is cheap insurance.
  10. Dimmers: Many times dimmers start to act up before total failure. Inspect for 1)free movement between clicks, 2)ambient temperature to touch, 3) full range of light from the bottom to the top of the dimmer movement. If it is just dead, some large dimmers have internal fuses that can go open.
  11. Physical Integrity: Most all manufactured lamps include metal parts. Many of them are soft metals such as brass or pot metal which can be fairly easy to bend or break. With that said it is not uncommon to have to occasionally tighten up some of the parts to keep everything in alignment. Do not over tighten the parts, the soft metal can break and be difficult to repair. FYI: Pot metal can be difficult to fix, so if you are thinking of buying a  lamp that is physically broken, you might think twice.
  12. Top capVentilation: As you can see in this picture of the top cap of the same swag lamp; there is virtually no ventilation for the heat to escape. Just for safety sake, I added some ventilation holes in the top cover.
  13. Light it up: The final test is to power it up and let if run. Depending on the type of lamp, I may let them run for 30 minutes or so with the highest rated bulb. Mainly looking for heat problems with components and if it smells.

Here is the finished lamp.  You can see the small holes I added to the top section for heat dissipation. Since heat is a major issue in this style fixture,  I used an LED bulb and it drastically cut down the amount of heat. LED bulbs have become a game changer for multiple reasons; look for a later post on LED bulbs.

Finished LampFinished Lamp 2

This article was originally published in my other blog found at DallasLampandLight.com

 

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