The flow is not really the issue the temperature is. As the manifold will have a thermostatic mixing valve set way below usual radiator temperatures.
If you can tee off the flow and return that feed the maniflold that would be better.
hi thanks to take the time to reply, it was actuallly a question following on from a pervious thread. i am starting from scratch in a small 3 bed house, ground floor ufh the rest rads. my original question was can the return from the rads circulate usefully after thru the ufh? a suggestion was using rads sized to 50 degree, operated as another zone. i am not sure if you cna run rads ufh and dwh on seperate circuits powered by a condensing boiler?
You cannot use the return from the rads as the ufh is a seperate circuit totally with its own pump.
The return from the rads have to return to the boiler they could not acts as a flow to the ufh as this would conflict the manifolds flow and return.
Hope that makes sense, however I see what you are trying to achieve with ufh using a lower temp could you utilise the return from the rads.
yes 'flufster', that is exactly what i was trying do, i was wondering how economic you make the system and it seemed a waste of 'warm' water on the return from the rads. i have read a lot of the heave hoing over which boiler is best, but am considering the veissmann 200 w2bc, it the bunf it says it can run 2 mixed circuits one un mixed (ie 2 ufh zones and rads) and i assume the dhw, i was wondering if you were well informed about this particular boiler, if this then negates the need for all the same manifolds and motorised valves you would normally expect to see in a ufh system, as it is all controlled by the boiler? i was also considering laying ufh heating pipes on the out door terrace under slate tiles as a solar heater, as it is france doesn't get too cold in the winter and the garden is full south in a walled garden, to preheat water, but was wondering the value of any solar system on a combi boiler?