Light Fitting Rating

I can't work out from your post whether it's the new fittings or the old fittings that are limited to 60 or 75 watts. However, the new LED bulbs will use less, so that's okay then.

Quite a lot of new LED fittings come with bulbs already fitted. These usually can't be replaced.

Maybe the simpler answer was just "yes"?

The limit is because of the heat generated, which is the actual wattage, not the "equivalent". No household LED bulb will approach the limit.

-- Richard

Indeed, the rating is to do with the amount of heat you can emit before melting / setting fire to the fitting.

Although LED bulbs in some fittings have been known to gradually cook themselves which shortens their life, well below the amount of heat needed to damage the fitting. It's worth thinking about ventilation of the fitting

- eg an upturned bowl will collect the heat, whereas a cylindrical lampshade open at the top and bottom will allow fresh air to circulate to cool the bulb.

Theo

I don't have any figures, but I'm doubtful about how significant this is. I suspect that the internal temperature of the bulb depends more on the design of the bulb itself than on the surrounding air flow. Cheap bulbs are likely to lack enough metal to conduct the heat away to the air.

-- Richard

Theo is right. I have some small ceiling lamps designed for G9 halogens. They point down, but can be angled slightly as well, are made of glass, and have no ventilation at the socket end. when I changed to G9 leds I was surprised at how quickly those bulbs died. I assumed they overheated, and tried a different make, but that also failed fairly quickly.

I eventually found that some Wilko 3.6W (33W halogen equivalent) lasted well without dying. In fact, I have a couple of spares which I haven't needed for 5+ years. Those bulbs are somewhat longer than the other G9s and perhaps aren't so susceptible to the heat.

With incandescent and halogens, they produce 90-95% of their rated power as infrared rather than visible light, which can escape somewhat.

LEDs tend to generate heat within the LED itself, so even if they are lower actual power to begin with, 40-60% of that power ends up as heat, with limited airflow for cooling, can tend to cook ...

essentially yes

You are correct

Also a tungsten filament is by nature hot up to about 3000K. Semiconductor junctions are good to about 125C, but higher temperature causes faster ageing, well below the tungsten temperature.

Persistently elevated temperatures can also damage other components like capacitors that are included as part of the lamp - if your capacitor dropper loses capacitance then it's not dropping so much voltage, you start to overvolt/overcurrent the LEDs, they run hotter, and conditions continue to deteriorate until something finally goes.

Theo