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Mr Pex thermal actuator issue

zharakeh Member Posts: 1
Hi all,

I have a strange issue that I hope someone can help with or maybe point me in the right direction. I have a 2 zone system that you can see in the picture. One zone is connected to a hydronic wall heater and another is connected to a radiant floor heating system. I’m having a problem with the zone on the left which is for the wall heater. I had a mr pex thermal actuator installed there that stopped operating so I replaced it with a new one. The new one comes from the factory partially open as you can see from the pic and is supposed to open similar to the one next to it when a call for heat is made. It is then supposed to close when heat is turned off from the thermostat. However, what’s happening is that I’m getting heat now all the time regardless of the thermostat setting. The new actuator remains in the same position all the time. I’m unable to shut down the heat unless I completely shut down the power or remove the actuator. I have tried using another new actuator and got the same issue. I even replaced the on/off valve, flushed the system, and installed a new thermostat with no success. What do you think could be the issue? Is the wiring correct? Thanks for your help.


  • GGross
    GGross Member Posts: 1,072
    most of these ship partially open and you need to apply power to them for about 6 minutes for them to unlock from the locked open position, then unhook power to let them close