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.

Where to wire a boiler controller

Options
I'm preparing to install a Tekmar 260 on my old Buderus G115/4. Should the controller be wired in series after the boiler service switch and low water cutoff, or in parallel with the low water cutoff after the service switch?

I assume the former, but I wanted to verify since I can't seem to find any pertinent wiring diagrams.

Thanks!

Comments

  • Zman
    Zman Member Posts: 7,607
    Options
    What is telling the boiler to turn on and off now?
    Wiring this may be a little trickier than you think. Your existing boiler enable switch gets tied to 11 and 12 on the tekmar. You do NOT want to start cutting into other circuits on the boiler.
    Where it gets tricky is re-establishing the connections from the t-stats, the tekmar needs 24VAC power to do this. Can you post pictures of your existing controls?
    https://s3.amazonaws.com/s3.supplyhouse.com/manuals/1302535675203/53188_PROD_FILE.pdf
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    CheckedAndRechecked
  • CheckedAndRechecked
    Options
    Thanks Zman! The current control is just a Honeywell L8148 Aquastat triggered by the 24V AC Honeywell zone valves with their end switches wired in parallel. From there, the aquastat controls the circulator pump and the Reillo propane burner.

    My thought was to remove the 24V trigger from the aqustat and move it to the Tekmar. Then Move the circulator pump to the Tekmar and connect the 260's output back to the Aquastat so that it could be used and an emergency high limit shutdown. This way the Aquastat still triggers the boiler, but the Tekmar controls the Aquastat and burner.

    Does this make sense?
  • Zman
    Zman Member Posts: 7,607
    Options
    That makes sense. You want to be sure the tekmar is in series with the high limit and any aquastat left in the mix. The tekmar wants to be in control with anything else just functioning as a safety if things get too hot.
    When you attempt move the zone valve end switches to terminals 1&2 on the tekmar, you will notice it won't work without power. You will need to energize the end switches.
    "R" on the transformer goes to one side of the end switch. The other side of the end switch goes to terminal . Terminal 2 wires back to "C" on the same transformer.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    CheckedAndRechecked
  • CheckedAndRechecked
    Options
    Great! Thank you. I would have certainly run into that issue head on.

    So the end switches on the Honeywell valves are dry contacts, but the Tekmar expects a voltage. This makes sense, because the aquastat powers the 24V end switch circuit currently. When I connect that aquastat to the dry contact on the Tekmar 11/12 terminals, this will trigger the aquastat like we're currently doing with the valves. Correct me if I missed something, but this all seems to line up.

    Looping back around to my first question on how to power the controller, it looks like terminals 5 and 6 need 120V line input to power the pumps. Would I take this power in series from the LWC or should I go from the service switch directly to the controller? Since the pump is higher than the LWC, I doubt this matters much in any case, since the protection wouldn't help me if the water level dropped under the circulator before triggering the LWC.
  • Zman
    Zman Member Posts: 7,607
    edited October 2021
    Options
    I never thought of tying it to the LWC, not a bad idea..
    I think it is personal preference, any power supply to 5,6 will work
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    CheckedAndRechecked