Actuator failure?

[melias]

While changing a thermostatic valve on our underfloor heating system, it became clear that of the 4 actuators on the manifold (there are 4 heating circuits), only one actually works.

The actuators are from Watts Industries. Is it likely that three of the 4 have failed, or is there more likely to be a problem in the electronic unit controlling the actuators? The system was installed about 6 years ago.

 

[melias]

One more question..The underfloor heating driven by a pump that turns on and off with the thermostat. Do I actually need the actuators? Couldn't I just leave the valves open and assume that hot water won't flow when the pump is off?

 

[Norcon]

If you not concerned about zoning then you can leave the circuits open.
However if a radiator circuit is fitted also or HW circuit then unwanted flow can occur through the opened loops

If flowmeters are fitted and indicating flow then the actuaters are working.