Comfort mode is usually set to a temperature significantly higher than eco mode. So, if the radiator has been programmed to switch from comfort to eco, it will likely switch off when eco begins because the room temperature will be higher than it needs to be.
The radiator will switch back on again when the room temperature drops below the eco set temperature. You can reduce the time the radiator spends switched off when stepping down modes by reducing the gap between the eco and comfort temperatures: increase comfort temperature or reduce eco temperature.
The radiator will switch back on again when the room temperature drops below the eco set temperature. You can reduce the time the radiator spends switched off when stepping down modes by reducing the gap between the eco and comfort temperatures: increase comfort temperature or reduce eco temperature.