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Boderus G115 return temp, Tekmar 360, Eire AT33000

Hi There,

I have a G115 oil installed in 2000. This is on an 8 zone radiant heat system. I have one mix circ that feeds 8 Zone valves. I also have a Domestic Aquastat that feeds a Domestic relay that fires the boiler. I “had” a Wirsbo Promix 101 controller that crapped out 3 weeks ago. My installer (friend) after a week or so, came by with a Tekmar 360 control which he seemed to be very unfamiliar with, which is surprising because he is quite sharp.

Ok, first issue was I had an Eire mod valve AT33000. That was overdriving whereas the tekmar does not have a time out. I changed the actuator to a AT3300T and solved that issue.

The Sensor is on the return of my boiler. Then there is a mix sensor between circ and ZV’s. I also have an outside sensor. The issue is the Tekmar is not opening up the mod valve so the mix temp and the mix target are seldom even close. This is sending cooler water up and of course cooler water back. The cooler water back (about 80-90 degrees F) tells the Texmar to protect the boiler and does not open the Mod valve. During this time, the supply temp is 175-180 degree F.

Tekmar has been helpful but not great. My big question arises form all this research. I seems that a person does not want to send cool water back to the boiler so you can prevent condensation. If that is the case, I am very confused. For the last ten years, my water temp has been anywhere from 85-120 going up to the zones, and of course returning anywhere from 75-110 or so. Is this a concern?? Now my current performance issue is how do I fix my chicken and the egg issue with the temperature. I felt I could move to the supply side however Tekmar manual clearly says if you use many devises to fire the boiler then go on return. Even though I don’t consider 2 devices (Tekmar 360 and DHW) to be “many” the section on the “return” clearly states you can go on the return if you only have 1 device firing the boiler.

Any thoughts you have would be so completely fantastic!!




  • Weezbo
    Weezbo Member Posts: 6,232
    edited December 2013
    i think it sounds like ,

    a step up, mixed by pass going back to the boiler, on the return of that zone would trick the control into behaving properly .



    sensor location then being a key element ...

    because if it is as you say , only that zone ,

    then whatever goes into a T must come out of a T ...

    think of it like this ,

    instead of having the hottest water going into the supply of the zone you will allow the coldest water of the zone to mix Higher on its individual path back to the boiler ,


    here is another approach ...

    depending on circulator location / s , .... sometimes , most times , set point mixed by passes at the boiler into the return can overcome cooler water temps returning to the boiler ....
  • Sparky99
    Sparky99 Member Posts: 2
    figured it out

    Hey Weezbo,

    Thanks for taking the time to respond. I did figure it out the other day. The reality is the Tekmar 360 is a great controller and very informative. The promix 101 was not as much. I discovered that intermittently the boiler circ would not run which allowed only mix temp water back to the boiler on occasion. This put the Tekmar into boiler protect mode and shut down the mod valve. In the end, I found and repaired a bad solder joint for the circ on the bread board of the boiler aquastat. Imagine that! Thanks for the reply

  • Weezbo
    Weezbo Member Posts: 6,232

    thats the ticket !

    you happened to catch it just right and like me you set to thinking ...lol mah poor brain cell..: )))
This discussion has been closed.