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  • Tekmar 256 installation

    Im in the process of trying to hook up the tekmar to my system but im running into a little trouble. I have a bunch of schematics in front of me but i cant seem to find what im looking for. Im trying to figure out the boiler demand and the boiler contact wires.

    here is what i have.

    Gas fired boiler, Slant fin S-120-DP
    Honeywell L8148E Relay
    Taco circulator pump
    3 zones

    Thanks Jeff
    Slant fin S-120-DP boiler
    L8148E aquastat
    3 V8043E zone valves
    Tekmar 256 Boiler control

  • #2
    Re: Tekmar 256 installation

    Boiler Demand on the Tekmar 256 is connected through T7 and C9 terminals

    Boiler Output is an isolated switch TT at terminals 5 & 6

    The L8148E that comes on that Slantfin is only rated for 2 zone valves (1.2A) Assuming of course your boiler room gets above 77 degrees, most do.

    Easiest way to wire is through a zone valve relay panel like the Taco ZVC403

    Comment


    • #3
      Re: Tekmar 256 installation

      Ok here is what i did. The zone valves are honeywell V8043's Both the red wires for the switch inside the valves run down to the L8148E and attach to the T and TV terminals. I disconnected the wires from there and ran them to the 7 and 9 on the 256. Than from the 5 and 6 on the 256 back to the T and TV terminals on teh L8148.

      Thats after 2 calls to Tekmar. Everything seems to be working fine at this point. I do notice the boiler doesnt cycle as much as it used to every time the Thermostat callled for heat. Now i guess i just have to do some fine tuning to it.

      Plumberscrack you say the L8148 is only rated for 2 valves. Why do you think they have 3 in the system? What are teh problems that can occur if any by doing 3? And what do you suggest i do to correct this?
      Is it just a matter of the relay for the valve motors drawing to much Amps form the transformer on the L8148 or is there something else?

      I should mention that there is an external transformer mounted on teh L8148 box. This runs the power to the zone valves. Its rated at 40VA
      Slant fin S-120-DP boiler
      L8148E aquastat
      3 V8043E zone valves
      Tekmar 256 Boiler control

      Comment


      • #4
        Re: Tekmar 256 installation

        Ok good, someone installed an external transformer to operate the zone valves instead of using the transformer inside the L8148E. If not, this would have lead to an early death of the limit.

        I'm not sure I would have wired as directed by Tekmar but if they say it's ok then fine.

        I'm guessing that when the boiler output is closed that the pump begins running before the zone valve actually opens. Not a big deal I guess with the Honeywell zone valve. It's a pretty quick opening unlike a Taco zone valve which takes about 90 seconds.

        Once all the tweaking is done you will notice a big difference in your gas bills

        Comment


        • #5
          Re: Tekmar 256 installation

          Yeah guess they figured the same as you did. That the load with all 3 zone valves would be to much.

          I think i agree with what your saying about how they told me to wire it. They werent really familiar with the L8148E when i called them. I had to tell them the sequence of events when the T/stat calls for heat. Now that i look at it it doesnt seem right. When it calls for heat the zone valves open. The circulator never runs untill the 256 tells the boiler to start. I guess what i should do is put teh wires back on the T and TV like they were and now i just have to find out what teminals actually go the the boiler to tell it to fire. That way when the T/stat calls for heat the The circ's run but the boiler doesnt turn on untill the 256 sees the need for it. The only problem was that Tekmar said that there cant be any voltage on the number & terminal. It has to be just a switch to connect 7 and 9.

          Any thoughts on that? should i wire the 256 to the B1 or B2 terminals? Im just not sure. Any input you might have would be great. If you like i can try to post the schematics so you can look at them.

          Maybe if i take the B1 off the L8148 and run that wire to terminal 5 on the 256 than run terminal 6 back to the B1 ?
          Last edited by lorunner1213; 12-14-2008, 04:55 PM.
          Slant fin S-120-DP boiler
          L8148E aquastat
          3 V8043E zone valves
          Tekmar 256 Boiler control

          Comment


          • #6
            Re: Tekmar 256 installation

            Jeff it's not working the way it should. Pump should come on and circulate water long before the boiler fires. This is where you gain the energy savings.

            After reviewing the wiring diagram you need to install a separate pump relay. You won't be able to use the relay inside the L8148E.

            It would be foolish of me to tell you how to wire it properly over the internet so please review this wiring diagram:

            http://www.tekmarcontrols.com/litera...robat/a256.pdf

            besides, I'm baking Tollhouse cookies and having a hard time keeping them from burning

            Pay close attention to page 2 how the zone valves and relay are wired.

            The L8148E is the most popular aquastat control manufactured. I can't believe Tekmar was not familiar with it.

            Comment


            • #7
              Re: Tekmar 256 installation

              I was actually thinking a relay. Looking at the schematics the one i think is the best solution is page 3. I would just have to rewire the zone valve switch and add the relay. that way i can leave the 256 terminals 5 and 6 wired to the thermostat terminals on the L8148. What do you think?

              To me schematic on page one will always have the circulation pump running even though there no call for heat, right?

              where can i pick up one of these relays if thats the route we need to take? Make and or model.
              Slant fin S-120-DP boiler
              L8148E aquastat
              3 V8043E zone valves
              Tekmar 256 Boiler control

              Comment


              • #8
                Re: Tekmar 256 installation

                Honeywell R845A

                Comment


                • #9
                  Re: Tekmar 256 installation

                  Ok so this relay will allow the 24 volt system to energize the coil and provice a path for the 120 volts to run the circ. pump?
                  Slant fin S-120-DP boiler
                  L8148E aquastat
                  3 V8043E zone valves
                  Tekmar 256 Boiler control

                  Comment


                  • #10
                    Re: Tekmar 256 installation

                    Yep

                    Comment


                    • #11
                      Re: Tekmar 256 installation

                      Awsome! You rule! Ok i think i got it from here. I think the wife will be happy. Wondering why the heat was taking forever to come on today.
                      Slant fin S-120-DP boiler
                      L8148E aquastat
                      3 V8043E zone valves
                      Tekmar 256 Boiler control

                      Comment


                      • #12
                        Re: Tekmar 256 installation

                        Plumberscrack before i go nutz trying to wire this relay is this right.

                        The T and T terminals on the relay are the low voltage (24V) conections. They switch the relay So run a white up to each of the T/stats. than the T/states come back and goes back to one side of the zone valve. The other side of the zone valves all get twisted together and connects to the red that goes back down to the other T terminal on the R845.

                        L2 and L1 are power from the fuse panel. L2 gets white and L1 gets black from that. than i can jump L1 to 4 and 3 goes to the black going to the circ pump. and the white going to the pump gets connected with the white on L2. Anything wrong with my logic here?

                        Thanks again, Jeff
                        Last edited by lorunner1213; 12-15-2008, 06:20 PM.
                        Slant fin S-120-DP boiler
                        L8148E aquastat
                        3 V8043E zone valves
                        Tekmar 256 Boiler control

                        Comment


                        • #13
                          Re: Tekmar 256 installation

                          Ok scratch that last post. Once i wired it up i now had a nasty hum from the R845A. I figured it out and rewired some things.

                          I left the original transformer and have that powering the zone valve motors with the thermostat as the switch. Than the End switch i have energizing the relay on teh R845A. Than i have the circ pump running off teh 3/4 terminals. and the 7 and 9 terminals of the tekmar 256 go to the 5/6 terminals on the R845A.

                          So as the t/stat calls for heat the switch inside the T/stat closes. It opens the zone valve. when the zone valve reaches its end and contacts the switch the switch tells teh R845A to energize the coil. Once the contacts on the relay are closed it turns the circ pump on and also activates teh relay inside the 256 boiler control to allow it to turn the boiler on if the temperature warrents it.

                          Hows that sound???
                          Slant fin S-120-DP boiler
                          L8148E aquastat
                          3 V8043E zone valves
                          Tekmar 256 Boiler control

                          Comment


                          • #14
                            Re: Tekmar 256 installation

                            Yea, that sounds right but does it actually work?

                            Those relays always hum a bit

                            The Taco ZVC503 would have minimized the wiring headaches

                            Comment


                            • #15
                              Re: Tekmar 256 installation

                              Originally posted by plumberscrack View Post
                              The Taco ZVC503 would have minimized the wiring headaches
                              To late now. I actaully hooked it up and i had a hasty hum. Than i realized that the T and T werent putting out 24 volts like i thougt. I first had teh T and T going to power the zone valves and thats why the relay was humming so bad. After about an hour of running diagrams and how it works in my head i figured it out. How it doesnt hum at all.

                              Yeah it seems to be working right. The call for heat opens the zone valve. once the zone valve is fully open than the R845 contacts colse and turn the pump on as well as tell teh 256 that there is a call for heat. Than based on the boiler temp the 256 can do what it needs to.

                              Basically thats what we wanted right?
                              Slant fin S-120-DP boiler
                              L8148E aquastat
                              3 V8043E zone valves
                              Tekmar 256 Boiler control

                              Comment

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