if two Senors (DS18B20) are connected to a Addon - there are two temperature actions are possible. Four different temperatures level can then be used to switch the relay. Via the I/O URL-actions, further commands can then be sent.
It is not very flexible, but maybe it is enough to switch a relay on/off according to the two temperature sensors.
Thanks for info,but this can be easy done by shelly programmersI .in arduino is couple line of simple code, two sensors and diff on number for example 10 and when is sensor 1 higher for 10C then sensor 2 make relay 1 on.
Whit add on they are not related unfortunately.
When you connect solar panel for water heating than you must measure panel temperature and boiler temperature and when is panel higher for 10 or whatever number than switch relay on.