Random spikes of above 100.000 W trigger switch to OFF

I have a electrically powered warm water heater (ca. 300L). It is switched using a HEIMAN Smart Plug HS2SK-Z (z-wave) using an automation which is triggered by time. The automation runs reliable but so far approx. once a month the switch is triggered to OFF before the programmed 4 hours. This early termination can happen after 3 hours or 45 minutes. Looking at the Energy consumption plot, this early OFF coincides with a measured energy spike of above 100K W (see screenshot example). The logs show no error messages. The message in the switches logbook is simply:

turned off
12:53:48 AM - 20 hours ago

which stands in contrast to the automation based switch off

turned off triggered by automation
triggered by time
4:30:00 AM - Yesterday

I would need help in the form of your communal experience/knowledge in figuring out if this is a real spike (of course not of 100k W) and I can be happy that the smart plug switches OFF or if this is a common glitch, which could be addressed with some filter. If the later is the case I will need help/pointers with writing such a filter.

Searching the forum, I found that the most likely experts are to be found in the Energy section, so I hope it is excused that while my question measures energy, it is only the primer for a problem.

Many thanks already!

Some basics:

  • Core 2024.12.5
  • Frontend 20241127.8
  • run in docker
    Smart plug in question:
  • HEIMAN Smart Plug HS2SK-Z

You should be really happy it switches off. That sounds like the switch’s overload protection kicking in, and you’re risking a fire if you keep it up.

It is not recommended to switch high power appliances directly using smart plugs because the relays in most smart plugs are not designed for heavy loads.

I’m sure someone with more electrical experience will show up and ask you this question: what are the power ratings of your heater and your switch?