Differential temperature thermostat for Solar water geyser/boiler

ESPHome
1

Hi Everyone,
I hope someone could possibly point me in the right direction.

I would like to create a differential thermostat with 2 Temp sensors(T1 & T2) and a relay to turn on external solar tubes pump for boiler/geyser.
Where if T1 >= T2 + 7C the Relay will activate. And when T1 <= T2 the relay will turn off

Would one use a Climate thermostat or use lambda?
From what i can tell on the climate components is that its more a 2 set point for low and high using temperature to activate heating & Cooling.
Would you be able to set the set point as a (T2 sensor reading + 7C) instead of set integer?

Thanks

2

Personally I’d probably just create a template binary sensor for each of your two criteria and then drive the relay state from that (on_press, on_release).

From memory thermostats aren’t very “templateable”.

3

Thanks, Thats what i ended up dong.
I used the template sensor for the temperature difference and passed that to the bang bang controller.
Its at least working for now.
Some small issues like i have to use the cool action instead of heat action to use positive range. If i use heat action id have to put it into a negative range, but nothing important

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