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Aquastat and outdoor wood furnace

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  • Aquastat and outdoor wood furnace

    I have an outdoor wood furnace that circulates to a closed-loop heat exchanger. Boiler water is heated from this exchanger with a Taco circ pump on the boiler. My problem is that my Honeywell 8124 Triple Aquastat doesn't seem to allow setting the hi and lo limit switches far enough to keep the oil burner from turning on. Almost all wood burning furnace manufacturers say to just set the low limit switch to 10 degrees lower than the temp of the water at the heat exchanger, i.e., the thermocouple should always sense that water temp is high enough to keep burner off but circ pump should still come on to push hot water through the zones. In theory this must work but with this aquastat it doesn't. I have to literally pull the wire off the circuit bd that goes to the burner to keep the burner from coming on. This is fine as long as I'm not away long enough for the outdoor furnace to go out, example: vacation. However, I'm looking for a better solution. I could eliminate the need to use the tankless domestic hot water option because the outdoor furnace provides plenty of hot water through another small heat exchanger at the tank input. I'd rather not buy another aquastat if possible. To summarize: regardless of how I set the hi limit, lo limit, and differential settings, the burner comes on. Thanks for any help.

  • #2
    Re: Aquastat and outdoor wood furnace

    Remove the blue wire from the low limit side of the 8124 and cap it. Don't argue with me. Don't ask any more questions. Just do it!
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    • #3
      Re: Aquastat and outdoor wood furnace

      ya that is right i agree with NHMaster3015 remove that the blue wire,












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      • #4
        Re: Aquastat and outdoor wood furnace

        Originally posted by NHMaster3015 View Post
        Remove the blue wire from the low limit side of the 8124 and cap it. Don't argue with me. Don't ask any more questions. Just do it!
        That's the way advice should be given.

        J.C.

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        • #5
          Re: Aquastat and outdoor wood furnace

          Originally posted by NHMaster3015 View Post
          Remove the blue wire from the low limit side of the 8124 and cap it. Don't argue with me. Don't ask any more questions. Just do it!
          This did nothing to solve the problem. It would be helpful if you were to have given some idea why you think this might have solved the problem (your bio says you are an educator, after all). After reading technical literature about the 8124 it seems to imply that the control wants to always keep the water in the boiler at a minimum temp range (between lo limit minus 10 degrees - and lo limit plus differential). It wants to do this regardless of whether or not there is a call for heat. Problem is the outdoor furnace heat exchanger just continues to transfer heat to the piping regardless of whether or not there is a call for heat and it does so upward (as one would think) and back through the return legs. Over time the water in the boiler cools down way below the low limit setting and the control wants to turn the burner on to keep it at the min range. I don't want this to happen. Instead, I want the circulator pump to turn on before the burner to pump water through the boiler (water which has been continuously heated by the exchanger) and then the controller will see that there is no need to turn the burner on because the water will be close to mid-way between the low and hi limits. The circulator would then continue to run until the thermostat says temp has been reached. The controller does not currently act in this way. Any help and understanding would be appreciated.

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          • #6
            Re: Aquastat and outdoor wood furnace

            Have faith in me brother, have faith. JUST DO IT. I'll explain later when the mood strikes. I promiss, I have not steered you wrong.
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            • #7
              Re: Aquastat and outdoor wood furnace

              Trust the Master

              Side discussion: Is the burner control interlocked to the pump via flow switch? (Boiler will only fire after proof of flow?) or does loop temperature drive the bus (boiler only cares about loop water temperature).

              hmmmmm I gotta work through the different control options in my cranium of course if this is a small all in one residental system I'm lost as I have never messed with one...

              Okie

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              • #8
                Re: Aquastat and outdoor wood furnace

                Originally posted by NHMaster3015 View Post
                Have faith in me brother, have faith. JUST DO IT. I'll explain later when the mood strikes. I promiss, I have not steered you wrong.
                I apparently didn't make it very clear in my previous post: "THIS DID NOTHING TO SOLVE THE PROBLEM".

                I left it as you suggest for several days with no difference in results.

                You'll explain later when the mood strikes?? Forgive me but this is, along with your previous posts, just downright arrogant and rude. I'm not sure where you were an "educator" but I doubt this is the way to respond to those who are looking for information.

                If there is anyone else out there who may have any ideas I would really appreciate hearing from them.

                So far I'm thinking I can't get the current aquastat (8124A) to do what I need done. I've either got to go with another control like an 8124M or an 8148, or figure out some independent circulation loop just to keep the hot water circulating between the boiler-side of the heat exchanger for the outside furnace water and the boiler proper. This seems to be the issue at this point. The 8124A wants that boiler to be at a set temp level and therefore keeps coming on to keep it at that level regardless of whether heat is being called for.

                Again, would appreciate anyone else who may have an idea and is willing to share (with an explanation).

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                • #9
                  Re: Aquastat and outdoor wood furnace

                  I don't know what you did, but if you removed and capped the blue wire from the low limit side of the 8124 then you disabled the low limit protection and that Will allow the circulator to run whenever it is called. if you don't have a control of some sort to call it, that is a different problem altogether and perhaps you should have been a bit more descriptive in your original post. I deal with kids all day long whining "why" at me. You asked a question and I gave you the answer. Short and simple. If you failed to provide all the information necessary that is your fault, not mine. Furthermore, I must assume that you installed the system yourself and perhaps should have taken the time to read the installation manual that came with the boiler or contacted the manufacturer for their recommendation. That said I have a sneaking suspicion that there is no control to circulate between the oil and wood boiler, or did you simply series pipe them? If so, you will always have problems with over and under heating.
                  Attached Files
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                  • #10
                    Re: Aquastat and outdoor wood furnace

                    Originally posted by NHMaster3015 View Post
                    I don't know what you did, but if you removed and capped the blue wire from the low limit side of the 8124 then you disabled the low limit protection and that Will allow the circulator to run whenever it is called. if you don't have a control of some sort to call it, that is a different problem altogether and perhaps you should have been a bit more descriptive in your original post. I deal with kids all day long whining "why" at me. You asked a question and I gave you the answer. Short and simple. If you failed to provide all the information necessary that is your fault, not mine. Furthermore, I must assume that you installed the system yourself and perhaps should have taken the time to read the installation manual that came with the boiler or contacted the manufacturer for their recommendation. That said I have a sneaking suspicion that there is no control to circulate between the oil and wood boiler, or did you simply series pipe them? If so, you will always have problems with over and under heating.
                    I get it now. You get off on insulting people and this brings out your arrogant attitude. The implication is that I'm "whining" like your students because I ask for an explanation. I wonder what your students' parents would think of your comment.

                    You like to think that you're so knowledgeable about this controller. I talked to a Honeywell engineer who is responsible for this line of controllers and he says your "fix" won't work. Alas, my statement is correct, your "fix" did nothing to solve the problem. The Honeywell engineers words were "most plumbers don't really know how these controllers work". His words, not mine.

                    You assume I installed this system myself and I didn't read the installation manual. Wrong again. It was installed by a licensed HVAC contractor. Problem is he retired and moved south and so I couldn't call on his wisdom. No one is left at his shop who understands how these controllers really work. Just like you.

                    I gave you every bit of information needed to solve this. I gave the Honeywell engineer the same information and he had a solution. You didn't.

                    You make alot of assumptions and make a lot of excuses. I wonder why others on this forum would give you a "Thank you" for poor, inadequate advice? Beats me.

                    From what I've heard and experienced on this forum from you it makes me wonder just how experienced you really are. Posting on forums doesn't make you an expert. Perhaps you should remember that and learn from it.

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                    • #11
                      Re: Aquastat and outdoor wood furnace

                      Originally posted by fwaid View Post
                      I get it now. You get off on insulting people and this brings out your arrogant attitude. The implication is that I'm "whining" like your students because I ask for an explanation. I wonder what your students' parents would think of your comment.

                      You like to think that you're so knowledgeable about this controller. I talked to a Honeywell engineer who is responsible for this line of controllers and he says your "fix" won't work. Alas, my statement is correct, your "fix" did nothing to solve the problem. The Honeywell engineers words were "most plumbers don't really know how these controllers work". His words, not mine.

                      You assume I installed this system myself and I didn't read the installation manual. Wrong again. It was installed by a licensed HVAC contractor. Problem is he retired and moved south and so I couldn't call on his wisdom. No one is left at his shop who understands how these controllers really work. Just like you.

                      I gave you every bit of information needed to solve this. I gave the Honeywell engineer the same information and he had a solution. You didn't.

                      You make alot of assumptions and make a lot of excuses. I wonder why others on this forum would give you a "Thank you" for poor, inadequate advice? Beats me.

                      From what I've heard and experienced on this forum from you it makes me wonder just how experienced you really are. Posting on forums doesn't make you an expert. Perhaps you should remember that and learn from it.
                      Sooooooo what was the solution to your problem or was that a naa naaa na n aaa naaa post?

                      I'm gonna have to agree with NHmaster on the fact that we are missing an accurate description of the current control system though it is understandable as you are not an HVAC professional.

                      Okie

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                      • #12
                        Re: Aquastat and outdoor wood furnace

                        Ok, So what did the honeywell engineer tell you?

                        Here's what I will tell you. If your installer piped the wood boiler in series with the oil boiler then the L8124 has no way of telling what the temperature in the wood boiler is. Unless a separate aquastat is installed in the wood boiler to call the L8124 the L8124 will operate exactally as is did before the wood boiler was installed. I am not an engineer, but I will bet you a whole lot of money that disabling the low limit on the L8124 will allow the circulator to run at any temperature. What your problem really is , is that the guy that installed the system had no idea what he was doing. As for my arrogance, perhaps you have a point, however, given the information that you supplied I gave you the answer. Anyway, what did the Honeywell guy say to do?
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                        • #13
                          Re: Aquastat and outdoor wood furnace

                          I don't think that your problem is your aquastat. I just finished installing an outdoor boiler for myself and so far it's working great. I installed a three speed pump from the outdoor boiler to the heat exchanger and a pump from the other side of the exchanger to the indoor boiler. Both these pumps run 24-7 and keep the boiler temp. at the same range as the outdoor boiler. I set the aquastat 10 degrees lower and so far so good. I am sure I will be tweeking it out as time goes on but right now I am very pleased.

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