Heat & fixture types?

We’re trying to figure out the best downlight fixtures for GU10 lamps (LIFX, Hue, etc.). Does anyone know when LIFX (or Hue, etc.) produce the most heat?

An incandescent dimmer typically produces the most heat @ about 30%. So it’s a bit of a bell curve with near 0 heat @ 0% and 100% with the most heat at 30%. Any idea if LIFX are similar? So all RGB all @ about 30% brightness should produce the most heat?


Hi LD1!

It is not recommended to use LIFX bulbs on dimmers at this current point in time, however regardless of dimmer state (assuming bulb is still online) then the highest power output is likely at 3500K @ 100% brightness.

The incandescent was an example. These will be constant voltage.

Within your lamp you have three or more dimmers. Dimmers (typically an SCR, DIAC, TRIAC or Varsister) produce heat, often a lot, as a byproduct of controlling the voltage to whatever produces light (incandescent filament, LED, etc.). The least amount of heat produced is likely at 0% intensity? 100% intensity is likely very low heat as well. What we need to know is what is the worst use case? What settings will cause your GU10 lamp to produce the most heat and thus be most likely to fail due to a fixture not allowing adequate heat dissipation?

IOW, what fixtures can we know will work reliably and which s/b avoided for someone who will use one of your lamps?

In this case we are looking primarily at two fixtures; Halo H36TAT and Halo H38ICAT. My guess is that the H38ICAT will work better since it has a larger space for heat to dissipate within, much more surface area to act as a heat sink, aluminum surface which should conduct heat better, and no paint.

The H36TAT is smaller, has less surface to dissipate the heat, and is painted which I believe will lessen it’s ability to dissipate heat.

The questions; are we correct in our assumptions about these and is the difference something that will make a realistic operating difference and so worth the extra cost?


LEDs and LED drivers within our bulbs are a completely different kettle of fish compared to traditional dimming methods. Essentially a PWM signal is used to change the brightness of the LED, this dimming method uses very little energy (just the efficacy and loses within the driver).

At 100% brightness is when the maximum power is used (thus max temp) :slight_smile:

It’s worth noting that per lumen, LED technology is far more efficient, and therefore less heat is generated than a standard incandescent or halogen bulb would. Even when you add in the electronics, a smart LED bulb should run cooler than an equivalent halogen.

LIFX did a blog post a few years back on this subject. @redding is there any chance of a retest with your current fleet of bulbs? I know the lumens/watt has improved, so I’d be curious to see if there’s a comparative heat difference between the newer and older bulbs too.

Thanks @redding.

Have you guys done testing of various fixture types (GU10 in this case) and do you have any recommendations on what works and what does not. We’ve asked your tech support group twice and both times were told that you had not done such testing, which really surprised us and raised significant concerns.

@jymbob, yes. But LED is also more sensitive to heat. An incandescent lamp can withstand very considerable heat build up with no negative impact. I believe the LED’s themselves can withstand considerable heat but the electronics for the drivers not so much. BTW, thanks for the blog link.

In your FAQ you state:

LIFX Lights are not designed for use in:

  • Enclosed fixtures that limit the flow of air and/or trap excessive amounts of heat

Almost by definition GU10 will be used in such fixtures. I can’t think of a fixture manufactured with a GU10 socket that is not enclosed. So, what is excessive? What fixtures have you tested with and will work properly with your GU10 lamp?


Fixture Tests

We tested three lamps (Phillips 5w (50w equivalent) Warm Dim, Phillips Hue White & Color Ambiance, LIFX GU10 multi-color Downlight), in two fixtures (Halo H36TAT, Halo H38ICAT) with two trims (Standard, Wet).

This was not a comprehensive test but primarily to determine the approximate heat performance of the two Halo fixtures.

Generally the lamps were allowed to burn for one hour by which time most had reached about their maximum temp.

A few of the results:


The H38ICAT interior and exterior remained considerably cooler than the H36TAT. However, the lamp itself (measured at the hottest spot found) showed less variation and was only about 20° cooler in the H38ICAT.

Wet (sealed) vs Std trim made little difference. This may have been due to using bare fixtures though both trims were fully set against the housing so the results in actual use should be similar.

In determining which color temp to use (assuming higher watts = higher heat) I found the following interesting:


Two questions from this:

  1. Are both fixtures OK to use? Or should we use only the H38ICAT?

  2. Will one of the fixtures do better from a WiFi reliability standpoint? I’d guess that the aluminum H38ICAT would do better than the steel H36TAT? With the H38ICAT there are two layers of aluminum though - the sleeve that the trim+lamp slide in to and the box itself.