Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Caleffi Z-One valves.

Is there supposed to be a resistor on these somewhere? I have five of these, two had failed end switches and were replaced with the newer reed / magnet. I'm still surprised that the other three microswitches are working. Well, no not really I am being sarcastic. I replaced the Burgess switches with Honeywell switches so instead of a cheap knockoff you get real wiping with real silver so they are ok. But I read somewhere that the reed switch heads should have come with a resistor to limit current through the end switch. My heads did not come with a resistor. Does anyone know if it is needed and what value it should be?


  • hot_rod
    hot_rod Member Posts: 22,479
    If you are using a Caleffi Z-one with the reed switch type end switch, the resistor is built (molded in ) to the switch now. It has been for several years.

    We also eliminated the need for a resistor when using power stealing t-stats.

    Read the directions on other brands of relay boxes, some still require you add a resistor to "shed" away that voltage with power stealing stats wired with two wire.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ChasMan
    ChasMan Member Posts: 462
    Thanks again. I bought these five just before the switchover, I had two go within a month so I bought two new heads with reed switches and I put new microswitches in the other heads. Not one problem in the last 10 years so I will just let sleeping dogs lie for now. I'm not using power stealing stats just a zone control. I Like these valves a lot. Just wish I could get the label upside right but you have been hearing that for years I am sure.