Tim the valve itself is crud free and the pin pushes and releases easily it is the head itself that is the problem.

Chris the room temp was set at 21C, Hive itself seems to do a good job of not letting the temp rise no more than +/- 1C. On its maximum setting the valve should not be closing until the temp rises at least 6-8C above that. The fact that it was still closed at 2C below the room temp setting means it has an inaccuracy of 10C that's some range? Looks like I will need a better valve. Any suggestions?

Richard