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0-10v 3 wire mix with 2 wire control, erggg!

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Agreene
Agreene Member Posts: 5
in Thermostats and Controls
so i have installed a johnson 3 way mix with 0-10vdc actuator to control my panel rad temp, problem is my honeywell AQ254 "add a temp" panel is 2 wire 0-10v and the actuator is 3 wire 0-10v. i have tried all kinds on different scenarios with the common leg but keep getting 13 volts to the actuator when using the common leg.



the panel has a 0-10 - and + terminals but the actuator has 24vac +, common, 0-10vdc, terminals.



Has anyone else tried using the AQ 0-10v output with a mix valve that requires 24vac to power up?



Thanks

Alex

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  • SWEI
    SWEI Member Posts: 7,356
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    24VAC

    power is needed to move the valve.  Either wire it to a new Class 2 transformer or tap the one feeding the controls, if there is capacity available.  Ground needs to be the same as the control reference, so tie the new one to the existing common if you do that.
  • Agreene
    Agreene Member Posts: 5
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    Powered up

    I have the 24v+ tied in to R on the aq and com tied to C and the 0-10 + tied to the 0-10, but I have nothing to connect the 0-10 - terminal on the aq to.

    I have tied jumping the 0-10 - and the C together but just makes the actuator buzz.

    Thanks Alex
  • SWEI
    SWEI Member Posts: 7,356
    edited October 2013
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    0-10V minus

    is your control reference.  If the controller does not have a separate one, it sounds like you may have ground noise.



    Looking at https://customer.honeywell.com/resources/Techlit/TechLitDocuments/63-0000s/63-9963.pdf beginning on p.153, I don't see any ties between the 24VAC ground and the 0-10V reference.  This is somewhat unusual nowadays, so try measuring AC voltage between terminals 2 and 6, then also between 2 and your120 VAC neutral at the transformer input.  Disconnect the transformer and measure the resistance between the 24VAC C terminal and the 120V N terminal. 
  • Agreene
    Agreene Member Posts: 5
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    Findings

    Ok, term 6 to term 2 is 14v AC, term 2 to neutral is 26v, c term of transformer to neutral is open line.



    Thank you SWEI
  • Agreene
    Agreene Member Posts: 5
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    ?

    So I spoke to Honeywell and JOhnson this morning, honeywell was not familiar with a 3 wire 0-10 actuator they wanted a schematic of the actuator, not something Johnson was willing to give to Honeywell (go figure). spoke to Johnson they suggested adding a isolation transformer to power up the actuator and share the common back to the - of the 0-10vdc.

    Is there a simple fix I'm missing here?



    thanks
  • SWEI
    SWEI Member Posts: 7,356
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    3-wire mixing valves

    Share a common between power and control lines.  Belimo is wired the same way.  Sounds like Honeywell wants a 4-wire valve.  Can you confirm that with them?  I believe that is probably the simplest fix.



    The 14V to ground might indicate a grounded center tap, but I don't think I've seen that in the controls world.
  • Agreene
    Agreene Member Posts: 5
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    fix or replace

    Honeywell only has knowledge of 4 wire on 0-10v. I also told them that Belimo works with 3 wire 0-10. i don't think the tech, was very knowledgeable in this type on controls work.



    Does grounding the common  side of the transformer do any good?



    the actuator can also be controlled by 4-20ma signal would adding the 500 ohm resistor change the function of the circuit?



    I'd like to find a simple fix, its in my own house and don't mind a work around but this is getting crazy, I can't believe Honeywell puts out a product that is incompatible with a couple of major actuator manufacturers.





    Thanks
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