The thin I don't understand is how will the programmer control the two underfloor heating zones if there is only one zone valve for the underfloor heating manifold? Does the electronics int the ufh box do this?
Then you shouldn't have a problem however I stand by what I say, you have missed out a couple of relays at the boiler connection to prevent both pumps firing up at the same time. There is the potential for the manifold pump to fire up when the HW/CH pump fires up depending on what control system is in place and the manifold almost certainly won't have a bypass valve.
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