Vaillant EcoTec 831 - Help with setup

Spoke to vaillant tech support, they got technical engineer to call me back, 45 mins on phone, he went through various settings on the boiler to ensure got 15 difference between d40 and D41 before modulation, had to read some figures in various settings, he worked out deltaT and flow rate and altered d0 to match flow rate of bungalow.. have to say since that always getting 15 difference on startup, also went through various settings on the vrc700, mainly double checking what was set. Altered lowest temp and max temp for flow to 15 and 65. Said heat curve normally in Uk ranges 2.1 to 2.8 but can be as low as 1.7 and mine is on 1.7 having automatically modulated down from 2.0

Figures crossed it will now improve usage and be more efficient. Currently today’s usage 84kwh