We have a house equipped with KNX, but apart from the basic setup, it is not being used. (Due to lack of software, we don’t even have access to the programming.) Installed in four rooms are dimmer actuators, which are now causing problems in the children’s rooms. About 15 years ago, when we moved in, simple lamps with conventional incandescent bulbs were installed on the ceilings. Since then, the small children who used to fall asleep in dim light have grown into teenagers who want LED ceiling lights instead of hanging fixtures.
Several LED ceiling lights we have tried so far do not work properly with the dimmer actuator and the dimmable light switch. In other words, the LED, if it turns on at all, switches on with a delay and then starts to flicker, regardless of whether the LED is dimmable or not.
At a lighting store we were told that these LEDs are not compatible with the dimmer actuator. Non-dimmable LEDs do not work either.
Can anyone clarify if this is really the case, and what solutions we could pursue? Thank you.
Several LED ceiling lights we have tried so far do not work properly with the dimmer actuator and the dimmable light switch. In other words, the LED, if it turns on at all, switches on with a delay and then starts to flicker, regardless of whether the LED is dimmable or not.
At a lighting store we were told that these LEDs are not compatible with the dimmer actuator. Non-dimmable LEDs do not work either.
Can anyone clarify if this is really the case, and what solutions we could pursue? Thank you.
M
Molybdean19 Nov 2025 21:51What kind of actuators are installed?
Hi,
the behavior of the LED lights in your KNX setup sounds very typical for older dimmer actuators of this generation. Those devices were mostly designed for resistive loads and only had limited compatibility with electronic transformers or modern LED drivers. Lamps that start delayed or flicker almost always indicate that the actuator does not reach the minimum load or is not compatible with the type of LED driver. Just because it says dimmable doesn’t mean these devices will work properly with any leading-edge or trailing-edge dimmer.
You mentioned that even non-dimmable LEDs are acting up. This is entirely plausible since the old actuator modulates the voltage anyway. In such a case, the cleanest solution would be to remove dimming from the respective channel and replace it with a switching actuator or to reprogram the dimmer output to operate like a relay, if your model supports this at all. Have you checked in the ETS project whether you can see which dimming mode is set, that is, whether the actuator can properly switch between leading-edge and trailing-edge? Without checking this, you’re basically in the dark.
If you hardly use the system anyway, it’s really worth considering whether replacing the four dimming channels might save you more headaches in the long run than trying to find compatible LED lights that work with a 15-year-old dimmer.
Good luck!
the behavior of the LED lights in your KNX setup sounds very typical for older dimmer actuators of this generation. Those devices were mostly designed for resistive loads and only had limited compatibility with electronic transformers or modern LED drivers. Lamps that start delayed or flicker almost always indicate that the actuator does not reach the minimum load or is not compatible with the type of LED driver. Just because it says dimmable doesn’t mean these devices will work properly with any leading-edge or trailing-edge dimmer.
You mentioned that even non-dimmable LEDs are acting up. This is entirely plausible since the old actuator modulates the voltage anyway. In such a case, the cleanest solution would be to remove dimming from the respective channel and replace it with a switching actuator or to reprogram the dimmer output to operate like a relay, if your model supports this at all. Have you checked in the ETS project whether you can see which dimming mode is set, that is, whether the actuator can properly switch between leading-edge and trailing-edge? Without checking this, you’re basically in the dark.
If you hardly use the system anyway, it’s really worth considering whether replacing the four dimming channels might save you more headaches in the long run than trying to find compatible LED lights that work with a 15-year-old dimmer.
Good luck!
B
borderpuschl20 Nov 2025 08:30As mentioned above, this is exactly where the problem lies.
I hope you have the project file. Then it would be easy to check what your dimmer actuator can do (switching between phase-cut leading edge and trailing edge, functioning as a pure switching actuator, etc.), and also replacing the actuator with a dimmer or just a switching actuator would be very straightforward.
If not, someone will have to set everything up again, which, from what it sounds like in your case, shouldn’t be too much work.
Where are you located?
I hope you have the project file. Then it would be easy to check what your dimmer actuator can do (switching between phase-cut leading edge and trailing edge, functioning as a pure switching actuator, etc.), and also replacing the actuator with a dimmer or just a switching actuator would be very straightforward.
If not, someone will have to set everything up again, which, from what it sounds like in your case, shouldn’t be too much work.
Where are you located?