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Hooking up a nest power connector to triple aquastat

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snackman1973
snackman1973 Member Posts: 1
in Thermostats and Controls
Tried many different combinations,  after reading the C wire was common and needed to be grounded,  I attached to the side of the box.  Still doesn't function.  The 2 thermostat wires coming out of the unit are green and white(pretty sure whoever hooked it up originally just used the green instead of the red bc the red isn't connected to anything up at the weird junction box that I've never seen before.  Hopefully someone has seen something similar in their travels

It's an oil burning system with baseboard heat

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  • HVACNUT
    HVACNUT Member Posts: 5,844
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    You're not getting 24 volts out of the aquastat. That part shouldn't get touched anyway. 
    What's the va rating on the external transformer? You might need a 50 va.
    You need 3 wires at the thermostat. R,W,C. 
    snackman1973
  • 109A_5
    109A_5 Member Posts: 1,386
    edited August 2023
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    Hello @snackman1973,
    Bonding the C wire to the equipment ground is kind of irrelevant for proper operation. The external transformer size may have to be increased to handle the extra load of the NEST thermostats.

    Are you using the C wire adapter box thing ? If so do you actually need it ?
    If not I would wire it this way.



    If you wanted to clean up the wire colors a bit.




    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    MikeAmannHomerJSmithCTOilHeatsnackman1973
  • 109A_5
    109A_5 Member Posts: 1,386
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    Hello @snackman1973,

    With NEST Power Connector. Just one NEST or all three zones ?




    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited August 2023
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    I bet @Robert O'Brien knows a way!
    Can’t find his article, but an AC Ready or Kool Kit w/transformer would easily work.
    Use that for your common, run 2 wires to T-T to close the aquastat switch.
    Edit: Found it.
    https://heatinghelp.com/systems-help-center/what-to-do-if-you-dont-have-a-c-wire-for-your-thermostat/

    There was an error rendering this rich post.

  • HomerJSmith
    HomerJSmith Member Posts: 2,448
    edited August 2023
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    If you have three wires (conductors) to the Nest, do it exactly as 109A_5 diagrammed in his first post and forget the adapter. You will need an aux transformer, 40VA-24Vac.
    The connections from the Taco zone valves to the aquastat is the same as before the Nests were installed.
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,016
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    Make it easy for yourself for wiring, easily available "C" connector and diagnostics. Use one of these below. The Taco ZVC405 and 406 and the Caleffi ZVR106 all have 80 VA transformers.





    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    MikeAmann

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