29-12-2011, 10:00 PM
No Mike you are spot on, that is exactly the effect I am getting. Once full gravity circulation is underway the HW tank is well on the way to reaching it's set stat temp. and the metal interface to the pipe on the cheapo stat is well up near the cheapo stats setting (85 C) and thus that stat will then cut in if 85 C is reached as it's body has already been preheated as it were, this then dumps excsesive boiler temperature water into the CH system and by that very nature the flow return is cooler than the boilers exit temperature thus lowering the temp. of the water in the boiler to below 85 C. All the water contained in the boiler is common to both the primary HW flow and the central heating flow, the cross flow arrangement is designed to effect a more even temperature gradient thoughout the boiler thus reducing possible large temperature stresses within the boilers metal plate construction.....I think!!
Lawrence.
Lawrence.
