When controlling inductive loads like contactors (relays), water valves or fans excessive voltage spikes are generated by load. Voltage spikes can be also generated by adjacent relays belonging to some other control system located in the same electrical cabin. This can cause Themo to get stuck not responding to commands any more. Themo will start working again after physical reset by power-cycle.
Solution 1
Voltage spikes need to be suppressed using external RC snubber. These components need to be placed in parallel to inductive load as close to the load as possible to maximize their efficiency. In case of several relays or valves RC snubber need to be placed to all of them.
Schematic 1. RC snubber placement to suppress noise from contactor controlling radiated floor heating.
Schematic 2. RC snubbers placement to suppress noise from water valves
Schematic 3. RC snubber placement to suppress noise from adjacent contactor controlling 3rd party circuitry on same power line
Solution 2
In case of excessive electrical noise in electrical cabinet from adjacent installations like LED power supplies, routers, controllers etc it is also needed to suppress high-frequency noise (EMI and RFI) for Themo to work reliably. For suppression snap-on ferrite beads/cores can be used. They generate a clearer signal in the intended circuit.
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Snap-on ferrite beads | Installation - more turns improves efficiency |
Schematic 4. Ferrite bead placement to suppress high-frequency noise
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