Vaillant echo tech plus 418 short cycling on hot water but OK for central heating. Best recommended settings

[Johntheo5]

It probably does modulate, but modulates based solely upon the return flow temperature. Much better if it modulates based upon knowing the actual temperature of the water in the cylinder, or how close it has got to the desired room temperature when in CH mode.

Boilers normally control on the flow temperature, a non modulating gas boiler and oil fired boilers trip the burner at the SP temperature, a modulating boiler trips the burner at normally SP+5C as obviously the control temp and cut out temp cannot be the same. I think some Vaillants can be switched on the d parameters to control on the return temp but I havent come across anyone who does yet.

 

[Harry Bloomfield]

Cylinder is set to 55c at the moment but I have tried 50-60c as well. The flow temperature on the boiler is set to 65c.
The thermostat on the cylinder is quite old style so not sure how can I confirm if water temperature is reached to the desired level in the cylinder. But water in tap is definitely hot.

Rotating the stat anti-clockwise, if it clicks, then the cylinder is still calling for heat input.

 

[Hairymelon]

Does it work ok with heating on. Does it circulate ok around the radiators ?