Hi,
When my HW and CH is on at the same time, the radiators take ages to heat up. When I switch HW off, the rads get hot very quick and reach the required room stat. This has happened ever since the boiler was installed, around 2 years ago, but it has never been resolved.
If the room temp was 17 and I wanted it to be 20, this would take around 3 hours which is not good. With the HW off, it would get to this temp within 30mins.
Hopefully someone might have an idea.
Thank you