The actuators on the UFH don’t immediately respond to signals from the UFH controller, there is a 2-3 minute delay between getting the signal and being fully open

Yup - mine do that. The UFH actuators aren't motors but little heating elements that warm up a wax capsule which in turn pushes the valve mechanism - rather like an ordinary TRV but extra heat opens the valve rather than closes it. I suppose they could be fitted with a microswitch to sense when the valve is fully open - but I've never seen one.


Normally (say with a gas boiler) it shouldn't be a problem as the boiler circuit will take that long (via the bypass) to get the water up to temerature anyway.


If it's an electric boiler that's only for the UFH, then the it would seem sensible to me to dispense with the blending value and just have a single circuit with one pump - a lot less to go wrong then. With a blending valve it might work with just one pump - I've sort of got that setup with mine, but it's fed from a thermal store rather than a boiler - but the pump is on the UFH side of the blending valve - when valve calls for heat there's enough "suction" to draw hot water into the UFH circuit from the thermal store.


  - Andy.

The actuators on the UFH don’t immediately respond to signals from the UFH controller, there is a 2-3 minute delay between getting the signal and being fully open

Yup - mine do that. The UFH actuators aren't motors but little heating elements that warm up a wax capsule which in turn pushes the valve mechanism - rather like an ordinary TRV but extra heat opens the valve rather than closes it. I suppose they could be fitted with a microswitch to sense when the valve is fully open - but I've never seen one.


Normally (say with a gas boiler) it shouldn't be a problem as the boiler circuit will take that long (via the bypass) to get the water up to temerature anyway.


If it's an electric boiler that's only for the UFH, then the it would seem sensible to me to dispense with the blending value and just have a single circuit with one pump - a lot less to go wrong then. With a blending valve it might work with just one pump - I've sort of got that setup with mine, but it's fed from a thermal store rather than a boiler - but the pump is on the UFH side of the blending valve - when valve calls for heat there's enough "suction" to draw hot water into the UFH circuit from the thermal store.


  - Andy.