Author: Wattson All-Lights
Understanding enclosed fittings, heat dissipation, and smart-dimming compatibility
LED lamps have transformed the lighting industry with their efficiency, long lifespan, and low running costs. But despite their reputation as “cool-running” and maintenance-free, LEDs are still electronic devices, which means they are sensitive to heat and sensitive to compatibility with different electronic devices.
A surprisingly high proportion of premature lamp failures can be traced back to two issues most people never think about:
A - Using LED lamps inside enclosed fittings, and
B - Pairing dimmable lamps with incompatible dimming systems
If you’ve ever wondered why your expensive LED bulbs aren’t lasting as long as promised, this guide will help you understand what’s really going on behind the scenes.
Heat Is the Silent Enemy of LEDs
Unlike halogen or incandescent bulbs, LEDs don’t radiate heat outward; they move heat backwards into the lamp body, where a heat sink is designed to disperse it safely.
But even a well-designed heat sink can only work if the lamp has somewhere for that heat to go.
What is an enclosed fitting?
An “enclosed fitting” is any light fixture that restricts airflow around the lamp, including:
• Glass or acrylic domes
• Bathroom and hallway oyster lights
• Decorative pendant balls (including marble/glass spheres)
• Outdoor fixtures with sealed covers
• Flush or recessed fittings with limited ventilation
Inside these fittings, warm air becomes trapped. With nowhere to escape, the LED’s internal temperature rises, sometimes significantly.
Why does heat matter so much?
LEDs are sensitive electronics. When they overheat:
• The LED chip degrades faster (reduced brightness over time)
• The internal driver experiences thermal stress
• Components can fail long before the advertised lifespan
Why LED dimming is more complex:
Incandescent dimmers were designed for a simple resistive load. LEDs, however, contain driver electronics, and every brand designs these drivers differently.
Symptoms of incompatibility include:
• Flickering at low levels
• Buzzing from the lamp or dimmer
• Lamps failing earlier than expected
• Limited or jumpy dimming range
• Lights flashing
Smart dimmers introduce even more complexity
Systems like Zigbee, Z-Wave, DALI-through-smart hubs, Shelly, Casambi, and other connected dimmers do not behave the same way as a traditional trailing-edge dimmer.
Some key points confirmed from manufacturer's technical teams:
• The dimming capacity listed on smart dimmers (e.g., “130W LED load”) is
often only tested on their own brand of lamps.
• Other brands may behave differently, even if labelled “dimmable.”
• Smart dimmers sometimes rely on a minimum or “holding current.” If an LED
lamp’s electronics don’t meet that threshold, the lamp may not dim correctly,
or may prematurely fail.
• Mixing different brands of lamps on one dimmer circuit increases the chance
of irregular behaviour.
How to Protect Your Lamps and Ensure Long Life
Here’s a simple checklist that prevents 90% of LED problems:
1. Check if your fitting is enclosed.
2. Only choose lamps labelled “enclosed-fixture rated” for enclosed spaces.
3. Verify dimmer compatibility - especially for smart systems.
4. Keep lamp brands consistent on the same circuit.
5. Avoid mixing smart dimmers with non-smart LEDs unless confirmed compatible.
Final Thoughts: LEDs Are Reliable — When Installed Correctly
LED lamps can absolutely deliver the long life and performance they promise, but only when heat and dimmer compatibility are taken seriously.
Enclosed fittings without ventilation will cook even the best lamp.
Smart dimmers without proper testing can confuse even the most advanced driver.
By understanding how LEDs behave thermally and electrically, homeowners, electricians, and designers can make informed choices that prevent premature failure and save money in the long run.
