2017-11-27

Replacing my light fixture's GX32D tube with a regular light bulb

I have a 1980's vintage light fixture on the outside of my house.  It uses a two-pin GX32D-2 fluorescent bulb, which is unlike the modern CFL bulbs you see today.  These GX32D-2 bulbs are super-challenging to find, and expensive too. 

Even worse than that, the GX32D-2 is a 22 watt bulb - that is a lot of electricity for a modern outdoor house light fixture.  And all that power is used for from dusk to dawn - about 12 hours a day.

My goal is to replace this decidedly old-school GX32D-2 bulb system with a traditional lightbulb socket and a commonly available LED bulb.

What is inside a GX32D-2 light fixture

My GX32D-2 light fixture has three major electrical parts: a ballast transformer, the 2-pin bulb socket, and the bulb itself.  If the lamp stops working, it can be due to a bad bulb or a bad ballast.   Usually I try a new bulb first, and if that doesn't work, I replace the ballast.

Nothing is inexpensive when it comes to maintaining these lights. Replacement bulbs, ordered online or from a specialty shop, can cost $15. A replacement ballast can be $12.  Bulb replacement is easy, but replacing a burnt-out ballast means removing the fixture and rewiring. Yuk.  I want to stop all that.

Original fixture setup, with ballast (top) and GX32D-2 socket (bottom)

My Retrofit Goals

My goal is to make a simple, clean and reliable conversion from the existing electrical components, with a minimum of spending.
  • Lower operational power expense by at least 80%
  • Ease maintenance by using a traditional bulb socket
  • Lower bulb replacement costs

Light Needs Analysis: Lumens versus Lux

I want to make sure that my new light set-up will provide as much light as the existing set-up.  The GX32D-2 bulb is rated at 1200 Lumens, but I don't need to replace it with another 1200 Lumen device to get the same brightness.

Lumens is the measure of all of the light leaving a bulb, but lux is the amount of light falling on a particular spot. One thing about my outdoor light fixture is that the light is supposed to shine light mostly downwards in order to illuminate the ground. But given the GX32D's vertical orientation in my fixture, most of the light is directed sideways, bounces around the fixture and gets converted into heat.  A lamp that directs more light downward will be greatly more efficient, as it will be brighter where it counts. 

I have a this handy light meter, so I can measure the actual light output to test different options.

Therefore, in order to get a baseline of the existing set-up, I measured the light output under the lamp at a distance of 1 yard.  The meter reports 160 lux. Any new bulb should shine 160 lux under the lamp.

Some options to fix the problem

So at this point I know what I want, but now the question is how to do it.  There are lots of solutions.  Here are the three that I looked into:

Replace the socket.  This is the solution I chose.  It means taking down the light fixture and removing the old ballast and socket, but this simple $5 lamp holder socket is the only new part that is required.


Replace the fixture. Another solution is to completely replace the fixture.  But I actually like my old fixture's style quite a lot.  It's made out of heavy cast aluminum, and so it is quite robust.  New fixtures are generally poorly made, or it they're not poorly made, they're very expensive. It's a shame to go throw this one away when the only thing wrong with it is the bulb it requires.

Install a bulb socket adapter.  There are socket adapters that can convert a 2-pin socket into a traditional socket.  But you still have to remove the ballast from the circuit, and the adapters are hard to find and expensive too.  This seems like the worst solution.

The socket conversion process

Here is the process I used to replace GX32D socket with a traditional socket.
  1. Removed the fixture from the house.
  2. Removed the baseplate that holds the ballast and socket
  3. Removed the socket and ballast from the baseplate
    • Repainted the baseplate a gloss white
    • Repainted the fixture a satin black
  4. Bought this Leviton lamp holder socket and screwed it into place.
  5. Wired up the new socket with a short (2 foot) length of lamp cord.
  6. Fed the cord through the baseplate and through the lamp.
  7. Reassembled and re-installed.
And there we have it! Now my light fixture uses a standard bulb and is at least as good as new!

The removed bulb, socket, and ballast


Same fixture, but now with a Leviton E26 socket retrofit.

Bulb Selection

Now that I had a fixture with a standard bulb socket, it was time to find the best bulb.

I started with the lowest wattage LED bulb I have laying around - a 3 watt LED bulb that I bought on Amazon.  I measured the light under my new fixture with my light meter, and it was at 169 lux... brighter than the original 22 watt bulb!  Although the LED is, over all, rated at 20% of the lumens of the original GX32D bulb, the new socket orients the new bulb in a very efficient way (downward) as opposed to the GX32D socket which oriented the bulb in the least inefficient way.  So my new 3 watt LED retrofit with a nearly optimal lamp orientation provides more light on the ground than the original 22 watt bulb that was in there!

Since this was the lowest wattage bulb I had, and since it threw plenty of light, I went with it.

Just for fun, I measured the actual power usage of the old and new bulbs on my kill-o-watt power meter.  The GX32D bulb plus its ballast uses 23 watts, while the new LED bulb only uses 2.5 watts - that's a huge 20.5 watts in power savings. Doing the math, this retrofit will start paying dividends in less than three months.

Conclusion

Replacing the GX32D-2 socket in my outdoor lamp with a traditional bulb socket and a 3 watt LED had many advantages and no known disadvantages.
  • saves about $40 a year in electricity costs
  • provides more usable light under the fixture
  • easier and cheaper to maintain, as the new set-up uses commonly available bulbs
  • parts cost was about $8 (for the socket and wire) and took about 15 minutes
The one thing I didn't do was install a photoelectric sensor.  If I ever have a reason to open up this fixture again, I might do that.  Or, imagining the colorful possibilities at the holidays, maybe I'll install a so-called smart bulb.

Update - Two months later

My updated fixture has been running for over a few months and is working perfectly.  It's winter as I write this, and now I see another huge advantage of the LED over the GX32D - light output in cold weather.  The old GX32D-2 bulb would get noticeably dim in freezing temperatures, but the LED is as bright and effective as ever.

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