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Should the circulator for the main loop always be on?

336mlk Member Posts: 17
Hello again. Buderus Boiler with Buderus DHW heater all controlled with older Logmatic 2109. I have four zone pumps the circ pump and the pump for the DHW. If all is supposed to be working, should the circ pump for the main loop be always on any time one of the zone pump comes on? For example this morning all the zone pumps were running but this but the circ pump was not so the pipe was not hot. To fix this issue I usually have to restart the boiler switch. (I also have disabled DHW Priority)

What I'm trying to understand is if the Logmatic is doing some kind of "process" to make it behave this way or if I most likely have something wrong with my sensors or the Logmatic itself. It doesn't make sense to me that the there is a call for heat which turns on the zone pumps but yet the circ pump is not on so the water the zone pumps are getting is cold. Since I am new to this stuff I wasn't sure if there was any other reason why the zone pumps would run but the circ pump would not run.

The boiler water temps are in the 150 range as expected.



  • GW
    GW Member Posts: 4,702
    I only have experience with the 2107, and on that control yes, the heat pump output is energized when you're below warm weather shutdown. So you may have the classic collision of European and USA strategies. Apparently whoever wired your system doesn't understand the control strategies. You would normally want your most occupied zone, or warmest zone operating off of the Logomatic control. Gary
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA