Measure: Raise the maximum phase current as far as the supply permits, see Section 9.2.3, “Basic settings” – or bring the heating circuit of this channel down to a smaller connected value. Put high-current zones on different phases; which channel is on which phase is described in Section 5.2, “Channels, phases and connected load”. How the Thermonom distributes the budget, and why this channel comes away empty, is explained in Section 6.8, “Power limits and power reduction”. If the connected load is permanently insufficient, please ask customer service.