My understanding is the UFH pumps only circulate the blended water in the circuits, there is a clear path through from flow to return and the UFH only takes primary flow water to make up the lost heat in the circuit. The flow and return to manifold will need balancing to 20 degree differential once the whole system can be run.
as it is they are probably not balanced and the return temp is being prematurely raised which will cause the boiler to cycle.
The hw is not working due to a very low resistance circuit (much lower than cylinder circuit) maybe as described above, or if what carrera is saying is true, reverse circulation through the cylinder.
the magna is the main pump and when you consider what it's doing, should be man enough. The Pipework should be up to the job if I understand the design.
My advise would be to tee in the hot water return independently to ensure it's not reverse circulating, double check everything in that circuit and the Pipework for blockage.
the boiler connections are 28mm and the internals are probably 22mm, it's the overall resistance not one small section of pipe that will probably be negligible.
as it is they are probably not balanced and the return temp is being prematurely raised which will cause the boiler to cycle.
The hw is not working due to a very low resistance circuit (much lower than cylinder circuit) maybe as described above, or if what carrera is saying is true, reverse circulation through the cylinder.
the magna is the main pump and when you consider what it's doing, should be man enough. The Pipework should be up to the job if I understand the design.
My advise would be to tee in the hot water return independently to ensure it's not reverse circulating, double check everything in that circuit and the Pipework for blockage.
the boiler connections are 28mm and the internals are probably 22mm, it's the overall resistance not one small section of pipe that will probably be negligible.
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