I have a ZBMINI (not -L) and use it to toggle my heating (2kW). In between I put a contactor because I trust it to be more safe. The problem is that sometimes it toggles a few times extra. Depending on the amount, the heating is on whilst the switch is off?

Is this caused by inductive kickback as described here? If so, how do I calculate the snubber size/value?

contactor type: A9c20732 - datasheet

heater type: convector 2kW

The heater does have an optional fan built in. Should I see if this has impact?

Is there a type of contactor that I can use that does not give inductive kickback?

  • \$\begingroup\$ Please provide a data sheet link to the contactor. \$\endgroup\$
    – Andy aka
    Jan 17, 2023 at 12:39
  • \$\begingroup\$ What is the 2kW heater? Please use the edit link to put this detail in the question. \$\endgroup\$
    – rdtsc
    Jan 17, 2023 at 13:11
  • \$\begingroup\$ And how are controlling the contactor? \$\endgroup\$
    – DKNguyen
    Jan 17, 2023 at 15:13
  • \$\begingroup\$ The ZBMINI controls the contactor via Home Assistant. \$\endgroup\$
    – geiregjo
    Jan 17, 2023 at 15:41

1 Answer 1


I bought an RC absorption circuit and put it parallel over my contactor coil. I believe the issue is resolved now. But time will tell.


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