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uponor mva zone end switch control problem

(3) Uponor 2-wire t-stat A3030101

(1) Uponor zone control board A3030101

(1) Honeywell Relay R845A1030

I received a call about some Uponor motorized valve actuators (A3020522) not turning the pump on. This job is radiant with 6-loops on a manifold with 6-motorized valve actuators (2-for each of the 3 zones).  The homeowner said the yellow lights would come on (signifying the call for heat and valve opening) and then shortly thereafter the red light would come on (signifying the end switch should be "made")

I asked the homeowner to take the two wires off the ES out (on the right hand side) and twist them together.  The pump came on. I assumed (I know, I know) it was a zone control board (A3030003) gone bad.

Took a board, changed it, same thing...I then humbly dug further.  I jumped R1 and R2 at the board - and it would pull in the pump relay R845A1030 and when I took the jumper off the relay would stay energized.  I jumped it with it wired up.

To further check the end switches I pulled a MVA off and energized the yellow wires and checked the red wires for continuity and the end switch was "made".  Then I noticed when I would jump a switch the red lights would get brighter.  It is almost like the end switches are only allowing partial voltage through or something like that.....

Anyone run into anything like this?  It is hard for me to fathom that end switches would make but not pull in the relay coil.

Please help - thanks in advance.


  • ChasMan
    ChasMan Member Posts: 459
    edited January 2010
    I had...

    The same sort of problem. The LED on my relay panel would light (dimly) however the relay would not fire. The end switch contact was only partialy making. The endswitch was a burgess microswitch and it was defective. The LED will light with only a volt or two and a few milliamps of current available. The relay coil needs full power. My Valve was a caleffi and zone panel is Taco.

    I found this interesting post.

  • BobbyG
    BobbyG Member Posts: 79

    wow - thank you for the info!  I really appreciate that!!!
  • Grote
    Grote Member Posts: 1
    A3030003 ES end switch problem

    The link provided in the previous post is dead.

    I've got the same problem as described in this thread and after three A3030003 ZCM's I can't get the ES to activate the relay.  Dim red LED's just as you describe as well. What was your fix for this issue?
This discussion has been closed.