Return temperature difference

[bos-mary]

Hello!

I want to make an automation that keeps constant temperature difference between Ariston_CH_return_temp and Ariston_CH_setpoint_temp, up to a maximum temperature for setpoint.

e.g. If Ariston_CH_return_temp is 25 set the Ariston_CH_setpoint_temp to 28. If Return_temp increases to 26 then Setpoint_temp changes to 29 etc up to a defined maximum for Ariston_CH_setpoint_temp.

How can I do that?
(a more elegant solution than manually create IF THENs for each value)

Thx