Old condensing boiler temperature control - optimum setting?

[Kotc]

I have an older Baxi Solo 18 HE condensing boiler which is working fine. It’s very basic with a boiler temperature control.

The boiler temperature control knob is very basic setting displaying low to high, turn clockwise to increase, anti clockwise to decrease temperature.

What is the optimum to set the temperature control knob for best temperature and efficiency?

The instructions doesn’t actually have any information on optimum setting.

 

[vulcancontinental]

Start from around the middle then on the coldest day you experience, if you find you are not comfortable enough, increase the setpoint incrementally until the radiators, if they are you heat emitters, supply enough heat. Waste of time giving temperatures as you have no reference on the boiler.