push button delayed response

[galaxy666]

Hi,

in my condo i have Merten actuators, dimmers for lights and SE MTN6214-4146 (8 buttons) + MTN6212-4060 (6 buttons). there is 3X MTN6214 and 7 x MTN6212

Recently one MTN6212 died completely (blue led is not on). Now, some 2 others become unresponsive and slow. takes them 2-5 seconds to switch on the light.

On other controllers it works fine (instant). also software control via knx gateway works instant.

what could be the issue? is it possible that SE pushbuttons are dying one by one? what is the expected lifespan? these are about 15 years old.

[Erwin-vd-Zwart]

@galaxy666 

Most probably your PSU is declining, can you check the bus voltage? I have seen perfectly working installations of +30 years but weak point is always KNX PSU..

[galaxy666]

Hi, thanks for the input. I measured 30.3VDC on multiple points on the bus just to be sure. Seems stable. anything between 29-31V should be fine?

My PSU is 160mA, should I go for 320mA to be on the safe side?
In case one day I decide to replace my 10 pushbuttons with some more modern touchscreens I assume they will draw more power?

On the bus I have 1 dimmer that dimms 4 lights, 1 light actuator that controls 7 lights, and 2 HVAC controller/actuators that control 2 Fan coil units and 2 water valves (these valves have separate PSU). And 10 wall pushbuttons. I added 1 usb knx interface (out of the original design by whoever did the sizing of the required power).

The faulty pushbutton has the following behavior:
Once I press any button, the blue status led switches off for random amount of time, nothing happens with the lights. Sometimes if i press the button again, the status led goes back on. But sometimes status led is dead. Then if I use another wall pushbutton that controls the same lights, then the faulty one's status led goes back on.
Maybe the faulty pushbutton causes havoc on the bus and makes other pushbuttons unresponsive sometimes?

EDIT: I found another dead wall controller. not responsive to button press, status led goes off when pressed, lights do not switch on/off. but when light is switched on via another pushbutton or via mobile phone, the "dead" controllers show the status of the corresponding light as on. and off when light is off' ed via phone.  anyone seen such behaviour? so they are fine as read-only status panel to see what is off what is on, as long as you dont touch them 🙂

[Thomas_Rohde]

Hello Galaxy666!
To measure the voltage on some points and to have there the right voltage level is already a good start.

But, when you measure and at the same time there is no action on the devices (in case of action they may consume more power) it can give the impression everything is fine.
If I would be in your shoes I would exchange the PS against a new and more performand one. At least to make test if due to this action the installation works as expected again.
Also, before you exchange the PS, you can use it for a test with the "dead" device. Means connect to the new PS the dead Pushbutton. Maybe it will work perfectly?! Which would be another indicator that something is wrong within the general installation itself.