rk05

Hi All Thanks for all the replies. I will adjust the timing to avoid overlap The manifold pumps are set to max speed. Should these be turned down, how is the speed determined? Thanks again

Hi, Yes there are overlaps. The DHW is on a timer. For UFH there is a thermostat for each zone (Heatmiser), which is set to different temperatures at different times of day. This issue occurs when all 3 manifolds are calling for heat and the DHW turns on from the timer. Thanks

Hi, S plan I think. There are 4 2 port valves one for each manifold and one for cylinder.

Hi there I have a 3 UFH manifolds, each has its own pump connected to a system boiler Vaillant 630, 30 Kw and a Joule 250L unvented cylinder. The thermostat on the cylinder has a digital temperature display. In the recent cold spell I found that when all 3 manifolds were on and water is being heated, the cylinder temperature never went above 45-47 degrees even when heating the water for 4 hours. Touching the flow pipe into the cylinder it’s not as hot as the manifold pipes. The pipes that go to the manifold and cylinder all come off the boiler flow pipe. When one of the manifolds is off then the water heats up much quicker and gets into the 50s. When a third manifold is then turned on the the cylinder starts dropping temperature with no hot water being used. I would appreciate any ideas on the cause of this and how it can be resolved. thanks in advance