Should my underfloor heating pump be on all the time?

Hi
More accurately , What I really mean is should the underfloor heating pump run continuously while the zone valve is open?

It seems to me that the pump should be on when the zone valve is open so the boiler can turn off and let the water keep pumping, as the normal water temperature is too high for underfloor and the boiler will turn off pretty quick as the mixer will return hotter water to the boiler.

Have I understood that right?
and
Does the zone valve control the pump directly?

thanks for you advice

The main CH system pump should be set on an overrun by the boiler, to allow excess heat to be diverted away from the boiler. Not necessarily the UFH pump though unless it's controlled by an UFH wiring controller or an output from the boiler that allows an overrun to be applied to it.

If the UFH is simply a 2 port valve and a pump feeding a manifold and the zones aren't controlled by a UFH controller that controls the valve and pump too, then usually the thermostat(s) would control the zone valve (2 port valve), when that opens then a switched live would be sent to the boiler and the pump for both to run. Once the thermostat is satisfied and tells the 2 port to close, it will shut down the UFH pump and the boiler.

The main system pump whether internal to the boiler or external out on the system would normally be set to overrun by the boiler control and a bypass will allow min flow through the boiler till excess heat is removed.

It all depends on how your system is set up.

Thanks for explaining that so clearly . After reading that I set the thermostat to off and sat by the U/F pump and waited to see if it turned off.
It took ten minutes to turn off, I had thought it was staying on all the time