I have a luminary with 12 light points for standard E14 bulbs and a LED dimmer in the wall.

Using Calex bulbs, I only need 6 bulbs, which I run most of the time at 80% light output (measured with the smartphone light meter).

I also tried Toshiba dimmable LED bulbs and I noticed that they produce a different dimming curve. Also, when adding a single Toshiba to 6 Calex bulbs there is incompatibility and all of them flicker alternatively (all the Calex on, Toshiba off, and then the opposite).

As result of the high price of dimmable LED bulbs in general, of the different dimming curves, of the potential incompatibility with mismatched brands and of the not always reliable lifespan estimates (especially with LED "filament" bulbs), I need to ensure that I won't need to replace all of them as soon as one fails.

I see two options: buy some spare bulbs or install more bulbs and run them dimmed further:

  • if I install 3 more bulbs I will need to run them at 60% instead of 80% light output, thus reducing the heat load on each one significantly
  • if I keep them as spare, I know that I will have compatible bulbs ready.

I am not sure about the advantages and disadvantages beyond the two obvious ones I mentioned. How to choose?

  • \$\begingroup\$ I would recommend you take a breath, relax, wait for a bulb to burn out, and then go buy a replacement bulb. In the 20 years while you wait for that bulb to burn out don't worry, every thing is going to be okay. About 10 years ago, I replaced every incandescent bulb with LED. None have burned out. My biggest concern about LED bulbs was the realization that I will likely die before the bulbs do. Rest easy, be well. \$\endgroup\$ – Misunderstood Sep 19 '18 at 21:35
  • \$\begingroup\$ @Misunderstood I wouldn't worry if it wasn't for the two E14 bulbs that died after less than 18 month with less than 3 hours per day on average... The failure resulted in a decreasing number of LED chips emitting light per "filament". The bulbs still work, just with maybe 10-15 chips out of 50-60 LED chips. The bulbs were no brand, not dimmable, mounted vertically (screw fitting on the bottom) in a floor lamp (like ikea.com/gb/en/products/lighting/floor-lamps/… sealed on the bottom) connected to a halogen dimmer glued on the max setting. \$\endgroup\$ – FarO Sep 20 '18 at 12:09
  • 1
    \$\begingroup\$ There are very few vendors I buy LEDs from. Chinese (no brand) are off the table. The Chinese are known to have serious issues with reliability. No reputable supplier will use them. Actually I am not a fan of LED light bulbs. I think people need to open their minds and see that light bulbs are a poor format for LEDs cramming too many LEDs in to a small area. \$\endgroup\$ – Misunderstood Sep 20 '18 at 17:46
  • \$\begingroup\$ @Misunderstood In my experience Philips, Cree and Osram bulbs burn out just as often as six or seven Chinese brands that I've tried. I am usually buying in packs of 20 and at least one of them fails within 3-4 years. Well, of course it is not the LED that fails, but electronics, which I suspect is made on the same Chinese factories for all of them. So, the question is very actual, in fact. My answer would be to buy 2-3 extra bulbs. By the time they fail there will be better product on the market. Most likely cheaper too. Remaining lights can be used in the garage, basement etc. \$\endgroup\$ – Maple Sep 29 '18 at 22:00
  • \$\begingroup\$ Having said that, this question, however interesting, is obviously off topic here \$\endgroup\$ – Maple Sep 29 '18 at 22:01

I don't have a good solution for you, I'm afraid, for the lamps you've got. The majority of LED lamps are a lot more complex than the simple incandescent lamps of yesteryear.

enter image description here

Figure 1. Phase-angle dimming control. Source: Dimmers for LEDs.

Depending on the internal circuitry of the lamps they behave differently to the short pulses of current around the switching point. Any lamps with built-in smoothing capacitors, for example will store the peak voltage and may not show much difference in adjustment between max and 50% settings. Variations in component tolerances - and there will be many as lamp manufacture is a very price sensitive business - will cause variations in response to the applied voltage. The LEDs themselves will have variation in VF, their forward voltage, from batch to batch.

enter image description here

Figure 2. The capacitor, C2, messes up the response of the lamp on a phase-angle type dimmer.

enter image description here

Figure 3. A possible solution. LED filament lamps

LED filament lamps, if available for your lighting fixture, may offer a good solution. These are WYSIWYG (what-you-see-is-what-you-get) in that there is generally no tricky electronics to deal with and the lamps behave reasonably well with dimmers. I only have one at home and its on a dimmer. For some reason, which I must investigate, it gives a brief pulse of light on switch-on of the dimmer but works normally thereafter. These lamps are aesthetically pleasing too. Check the colour temperature of the lamp you choose as many are deliberately warm to mimic the incandescent and, as is often the case, the warmth may be overdone to make sure the consumer feels s/he is getting good value!

I have written a little more on the topic in the articles linked above.

  • \$\begingroup\$ I used visosystems.com/products/flicker-tester to test the flickering and it's very limited, therefore I would exclude a simple (as in fig. 1) dimming. Nevertheless, the question is about the choice spare vs more (effective! not phase angle...) dimming. \$\endgroup\$ – FarO Sep 19 '18 at 11:30
  • \$\begingroup\$ OK. I did explain in my first sentence that I hadn't got a solution for your problem. You didn't link a datasheet for the dimmer so I had to assume a simple triac phase-control dimmer. The lack of flicker could be due to the internal capacitance and the purpose of my answer is to explain the why you might see the effects and offer a solution. Whether or not to keep spares is a maintenance issue rather than a design issue and is verging off-topic for this site. In any case, when your three spares are used you are back to the original problem. \$\endgroup\$ – Transistor Sep 19 '18 at 11:38

Not the answer you're looking for? Browse other questions tagged or ask your own question.