Heating partial load/ range rating

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Hi Folks,

Hope you can advise.

Keen to reduce usage/cut bills.

How do I find the range rating on Vaillant Eco Tec pro 28? Looking to see if it's auto or should be lowered? (To what?)

I'm in a top foor/2nd floor 3 bed flat all on one floor, built around 2000 and I've 10 radiators. Gas does rads and hot water and electric shower.

I know everyone is different but just for info.
Also been tweeking flow temp, down to 46 heating on all the time, radiators 18 overnight 20 daytime (Tado) using about 40 kWh. Based on a heat geek "heating on all the time or not " on YouTube. Tried this last winter was only slightly more expensive than heating some rooms some time.

Thank you