Hello,
I am looking for a developer from the Nuki team who could investigate what appears to be a long-standing bug in the Nuki Opener. After extensive testing, I believe I have finally identified the root cause.
My building uses a Fermax VDS system, and my apartment is equipped with a Fermax 3390 (3-wire) intercom.
Whenever I connect the Nuki Opener, several neighbours lose the ability to use their intercom correctly. Disconnecting the Opener immediately restores normal operation.
Unfortunately, this issue has become very serious. The condominium management is now threatening to permanently disconnect my intercom because they consider my Nuki Opener to be disrupting the building’s intercom network. I would therefore greatly appreciate the help of your engineering team in identifying and resolving this issue.
According to the official Fermax VDS documentation, the communication bus must operate at a minimum of 16 V to ensure reliable communication over long cable distances. This is why the voltage level on the data bus is critical.
After taking voltage measurements, I found the following:
Without the Opener connected:
- +/ - = 18,1 V+/ L = 1,7 V**-/ L = 16,5 V**
With the Opener connected:
- +/ - = 18,1 V+/ L = 2,5 V**-/ L = 15,5 V**
The data bus normally operates at approximately 16.5 V, but as soon as the Opener is connected, the bus voltage drops below the 16 V minimum specified by Fermax, while the voltage between + and L increases. This coincides with the communication problems experienced by several apartments in the building.
My wiring exactly follows the official installation guide:
- Red + Yellow connected to the incoming L line.
- Black connected to -.
- Green + Orange connected to the L terminal of the apartment intercom.
My current hypothesis is that the Opener is drawing approximately 1 V of the energy from the data bus or altering its electrical balance, which disrupts communication on the Fermax VDS network while injecting this voltage into the opposite polarity.
If this hypothesis is correct, it may simply require correcting the direction of this voltage injection so that it is applied to the proper polarity instead of the opposite one.
Of course, this is only a hypothesis based on my measurements, and I would greatly appreciate it if a developer could confirm or disprove this analysis.
If this is not the actual cause, could someone from the engineering team please investigate why the Opener causes the building’s intercom network to malfunction?
I would also like to point out that the official Nuki documentation states:
“Four AAA batteries power the Opener. By using batteries, we ensure that the Opener does not draw power from the intercom system. This prevents power theft.”
However, based on my measurements, this does not appear to be the case with the Fermax VDS 3-wire system.
I would be very grateful if someone from the development team could investigate this issue. I can provide additional voltage measurements, photos of the wiring, or perform any further tests that may help identify the problem.
Thank you very much.
