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Aquastat question

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by McKraut, Nov 22, 2013.

  1. Clarkbug

    Clarkbug Minister of Fire

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    Just to be clear, your oil boiler is OK to operate in cold start, correct?

    Also, you are changing the low limit at the Aquasmart, not the Tekmar? They appear to have several features that overlap.

    What I am wondering is if the Tekmar is sending a "Stage 2" burner signal. When you flipped the switch to run the oil boiler for us manually, was there a "2" on the Tekmar display? I wonder if there is a time delay between stages 1 and 2.

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  2. R Mannino

    R Mannino Member

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    Take a jumper wire and jump T - T on the Aquasmart, if the boiler fires, that proves there is no signal for heat. If this is the case the issue is the wire either from the Tekmar to the three way valve, or the valve to the Aquasmart OR the way it's wired through that three way valve.
    ewdudley and Clarkbug like this.
  3. McKraut

    McKraut Member

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    The system designer told me the Buderus was the boiler to use. I assume he knew what he was talking about. I hope he knew what he was talking about. How can I find out? I have a Buderus G215. I will re-read the manual and see if it specifically states anything about it.

    When the TEKMAR has the "1" on the display, there is no activity on the oil burner. The only thing the Aquasmart displays in the water temperature. When the "2" icon pops up, the 3 way valve closes and then the boiler does/does not fire.

    Yes, I am changing the low limit on the Aquasmart. All the settings in the TEKMAR are the settings provided on the schematic.

    Thanks again,

    Bob
  4. ewdudley

    ewdudley Minister of Fire

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    I think you've proved the Tekmar and three-way valve are working correctly, but it would be great to make certain. Definitely want to try RManni's suggestion and jumper T-T to the Aquasmart and see what happens with and without low limit set to OFF.
  5. McKraut

    McKraut Member

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    Just finished testing it and this is what I saw. When I jumped T-T on the Aquasmart with the with the low "off", the burner did kick on. So as RMannino suggested above, did I wire the zone valve wrong?
    Since you understand the interaction between the TEKMAR and the boilers, I have another question for you. The TEKMAR will call for heat from boiler number 2 even when boiler 1 is still hot. I checked a few minues ago when I was testing the aquastat. The zone called for heat and the circulator turned on. After 5 minutes, the TEKMAR said it was calling for heat from boiler 1. In about 2 minutes TEKMAR called for heat from boiler 2 and this kicked on the oil burner. I ran outside and checked the temp on the EKO and it was idling at 188*. Is there a setting in the TEKMAR that can be changed to correct this?

    Thanks again,

    Bob
  6. R Mannino

    R Mannino Member

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    Give me some time to read the Tekmar manual. More than likely that's where your "issue" is.
    FYI Buderus is a great boiler.
  7. Clarkbug

    Clarkbug Minister of Fire

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    Hmm, thanks for the results McKraut. I see something else that is troubling. Stage 2 demand on the TEKMAR closes your three way zone valve, and that should then close the TT terminals, firing the oil boiler. But that has also closed your wood heat loop. This would be great in an either/or situation (either wood or oil), but the TEKMAR sees the two stages as working together. This obviously isnt the case with the way the system is wired up. If it calls for oil, it will close off the feed from the BioMass, and that will sit there and idle.

    I quickly skimmed the TEKMAR manual, but couldnt immediately find the setting to adjust for the time delay between Stage 1 and Stage 2. Looks like it might auto-adjust depending on the outdoor air temp, and the difference between the supply temp and target supply temp.

    But that still doesnt explain whats up with the aquastat (your original question). It fired when you jumped the TT terminals, but it sounds like you also may want to check how the ZV is wired up. Should be an endswitch on there that makes when the valve opens, and the wire connected to TT should be connected to those terminals. The idea being that we can work backwards from the terminals to figure out the issue. Jumper means boiler will fire when it has a call for heat without the low limit in place. So, we trace it back to the ZV, since thats the next junction. If thats OK, then we move up the line to the TEKMAR.

    Agree with Mannino, the Buderus is a great boiler.

    Your designer put together a great system for you, but great gravy is there a lot going on there! As you can see, its a real treat to try and toubleshoot :)
  8. R Mannino

    R Mannino Member

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  9. McKraut

    McKraut Member

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    Y
    Yes it is "2STG". Just to be sure when I was testing your recommendation about jumping T-T this morning, I went into the installer mode and verified that I had entered all the settings the designer recommended. Thank you again for taking the time to look at this for me. I really do appreciate it.

    Bob
  10. McKraut

    McKraut Member

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    Tomorrow I will be off all day and I will work with the wiring on the zone valve and see if I may have made a mistake. From what I read in the manual for the TEKMAR, there was not a lot of user defined settings to adjust. I have contacted TEKMAR and have not gotten any response from them. I am going to contact them again tomorrow. Thank you for all you help.

    Bob

    I wish the fella that designed it was still around to help. It would have made this a lot easier!!
  11. Clarkbug

    Clarkbug Minister of Fire

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    You have a very robust system, its just hard to troubleshoot from afar!

    Just focus on solving one issue at a time, and its easier to help troubleshoot it. For the TEKMAR, make sure you go into installer mode to play with your settings.
  12. ewdudley

    ewdudley Minister of Fire

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    A couple things have me wondering.

    The 'Boiler Supply Temperature' sensor (no, not the one on the wood boiler, the one on the 'Supply Header', so ignore the label and think of it as a "Supply Header Temperature' sensor) is used by the 401 to modulate the supply header temperature by cycling the wood boiler and engaging stage two according to its whim. That's fine except with four load circs it looks like stage two could kick in too easily. Of course the Tekmar sheet gives no detail whatsoever on what the criteria are for engaging stage two, so there's more than a little guesswork in play.

    So stage two kicks in, which presumably energizes (unlabeled) 'Zone Valve 24VAC'. Now the NO port of the ZV is from the oil boiler, so when ZV energizes the port from the oil boiler is closed, the port from the wood boiler is opened, and the end switch from the ZV sends a call for heat to the oil boiler by closing oil boiler T-T. So now we do get heat from the wood boiler for as long as the supply header stays cool enough, but once the supply header gets hot the ZV de-energizes, turns off the oil boiler, and begins to draw from the oil boiler. Lather, rinse, repeat. Am I reading the drawing right?
    Last edited: Nov 27, 2013
  13. ewdudley

    ewdudley Minister of Fire

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    Take a look at the 401 test modes that are available. You can cycle through the functions and pause wherever to investigate behavior.
  14. McKraut

    McKraut Member

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    This is the way I have it wired from the TEKMAR to the zone valve to the oil burner aquastat:

    Tekmar: Zone Valve: Aquastat:

    Red -------------------------------------------- Blue------------------------------------------Red
    Black-------------------------------------------Brown
    Black-----------------------------------------Black

    I reversed the wires on the zone valve and tried:

    Tekmar: Zone Valve: Aquastat:

    Red -------------------------------------------- Blue------------------------------------------Red
    Brown-----------------------------------------Black
    Black-------------------------------------------Black

    This gives the exact same results.

    I attached the actuator product information.

    Thanks again,

    Bob

    Attached Files:

  15. McKraut

    McKraut Member

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    I totally forgot that part of the schematic I posted is wrong. I just realized it when I was reading your description. After I had talked with the guy that designed it, I noticed that on the diagram the direction of water flow was wrong and the NO/NC was reversed. He said he would correct it on the schematic, but he never did. I know it was wrong, but there was no way you could have known. I am very sorry about the confusion.

    The zone valve is set up so that NO is for the wood boiler and the oil boiler is normally closed.

    Bob
  16. ewdudley

    ewdudley Minister of Fire

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    I'm confused. Wiring diagram shows two wires from 401 and two wires to aquastat.
  17. McKraut

    McKraut Member

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    This didn't post correctly. The spacing is off from how I typed it. I will redo this in Word and attach it.

    Bob
  18. R Mannino

    R Mannino Member

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    The only question I have left is: can the 401 through stage 2 activate the zone valve it's connected to?

    I also think EW is onto something with the boiler sensor location, it may be factoring into this issue.
  19. McKraut

    McKraut Member

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    I attached the spacing the way I had posted it, not the way it showed up

    Bob

    Couldn't post it as a Word or Excel file. It's here as a txt file

    Attached Files:

    • zone.txt
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  20. Clarkbug

    Clarkbug Minister of Fire

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    Bob,

    Move the wires coming from the TEKMAR to the ZV back to where they were. Thats a separate leg of wiring to track down. If previously it was moving the valve correctly, no sense messing with that connection.

    Looking at the PDF you posted of the ZV, do you have white, orange, and grey wires or connections that you can use? Or only blue brown and black?
  21. ewdudley

    ewdudley Minister of Fire

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    Code:
                Tekmar:                          Zone Valve:          Aquastat:
    
    INPUT_POWER_C--------------------------------- Blue
    INPUT_POWER_R-----STAGE_2_TERMINAL_LOWER-------Brown----------------Red (TR or TW)
                      STAGE_2_TERMINAL_UPPER-------Black----------------Black (vice versa)
    
    It's a plain old three wire zone valve, needs three wires to supply power plus activation contact.

    STAGE_2_TERMINAL_UPPER and STAGE_2_TERMINAL_LOWER terminals are interchangeable as long as the wire that comes from INPUT_POWER_R continues on to ZV Brown.


    Red and Black wires going to aquastat are also interchangeable.
    Last edited: Nov 28, 2013
  22. Clarkbug

    Clarkbug Minister of Fire

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    Thanks EW. I couldnt figure out if the end switch was a separate set of terminals (or was supposed to be) or not.

    I think whats throwing me off is that only two wires are shown on Bob's schematic, and in the text file.
  23. ewdudley

    ewdudley Minister of Fire

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    Same here. The VC type shown in the sheet McK posted does not jibe with NRT drawing. Plus, for me at least, three-wire zone valves with separate 24VAC sources involved coming from both the aquastat side and the 'thermostat' side has always been confusing.

    Speaking of NRT, here's an interesting quote from their webpage:

    Last edited: Nov 28, 2013
  24. McKraut

    McKraut Member

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    Do you know of any actuator that is only 2 wires and will work in this situation?

    Bob
  25. McKraut

    McKraut Member

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    I contacted 3 different people at TEKMAR trying to get some help from them. I got no response from anybody. Any idea on who to contact to get this figured out? I am running out of options.

    Bob

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