The LED vs Heat

Heat is a real enemy to the LED whether it is a replacement GU10 or a full luminaire so it is a constant battle to achieve a good design to reduce heat whilst achieving a high lumen output.

How often do you see GU10s looking very sorry for themselves?  Looking blue? Looking a bit jaded?  And this can happen after just a few hundreds of hours.

There are a couple of reasons; first, the design/quality of the lamp is simply very poor and it has failed after a short period or second, the lamp has overheated causing premature failure.

It is less likely these days for the lamp to be of poor design as manufacturing techniques have improved and component prices have come down.  You will notice most GU10 lamps have some sort of heatsink – or fins – around the LED and the miniature power supply is built into the end.  In free air this is almost certainly adequate – ensure good circulation and the heat is taken away from the components.  However, the majority of these lamps get used in the popular downlighter which is very effective at preventing good air flow past the fins.  Not surprising, really, as they were designed for halogen lamps with temperatures up to 700deg C with no need for cooling.

These are usually installed in ceilings with next to no airflow, trapped between the ceiling and the floor above and hidden under layers of insulation.  These areas get hotter and hotter, particularly in summer, and can quickly exceed the safe ambient temperature required around the lamp, typically 35degC. Be aware that whilst the ambient air temperature you can measure may be 30deg C, (apparently “safe”) the important ambient around the lamp itself could easily be 30 or 40 degrees higher, well in excess of safe operating limits for the components.  It will be far worse when used in the fire hood often required to meet fire regs.

The solution? Don’t install replacement lamps in luminaires designed for traditional light sources as they can’t keep ventilate but if you do, make sure there is adequate air flow to keep them cool.

Ideally use a complete luminaire designed specifically for LEDs.  These will be designed with LED technology in mind and will achieve much higher efficacies than replacement lamps (>100lm/W compared with 50 or 60lm/W)