Not sure what the TMV is set at right now, it was set so as to give an O/P temp into the 70's (actually I think it's around 70˚) so as to heat the store top-down, but not trip the boiler out at 82˚.
The TMV is to maintaina set tenmp into the return. If the boioer hasa delta-T of say 15C, leave the boiler on full, 80C, and set to 65C. Highest efficiency is when the return temp is lowest it can be. This is just over the dew point to stop condensing. Setting to 60C is just above it. If the boiler condenses, it will rot the insides.
