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Thread: How do you add a common wire for Nest

  1. #1
    Junior Member

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    How do you add a common wire for Nest

    I have a Honeywell 8148J aquastat and I want to add a common wire for my Nest. Does anyone know what terminal to connect the common wire to on the aquastat?


  2. #2
    HVAC Thermostat Specialist

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    What terminals are the existing thermostat connected to? Can you provide a picture of the aquastat terminals? It does not appear that the 8148J has a common terminal. You could just connect the common wire from the Nest to the cassie ground of the 8148J.

  3. #3
    Member

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    If what I saw online is correct one of the 24v burner terminals should be common, B2 would be my guess.

  4. #4
    Junior Member

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    I hooked the c wire up to the z first and than the T terminals on the aquastat. In both cases the Nest validated the hookup, but failed to work properly. Each time you demanded heat the Nest displayed a 3 minute countdown. At the end of the countdown the unit turned orange (for heat) for a second and then reverted back to the 3 minute countdown. When working normally there is no countdown.
    Click image for larger version. 

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  5. #5
    Junior Member

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    In the previous post I meant the Tv terminal, not the T terminal.

  6. #6
    Junior Member

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    Figured the issue out.

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