We've had some new rads and a new boiler installed. We had an extension a few years ago and some new rads were added but were teed off in slightly smaller pipe than the rest of the house. Now these rads worked perfectly well with the old Baxi 70FF but since we've had the new Micron 70FF these rads have been much cooler. The valves are fully open as they're last on the pipework. The rads in the rest of the house have supposedly been balanced