how connect aprilaire model 700 humidifier

[rgaila]

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Original Poster: Pat&Kitty Shirk 

need to know how to wire and control aprilaire model 700 with nest gen 3 thermostat

[BatraD]

I have the same issue. Have the * wire going to one leg of the April air and second going to C wire in the board. Nest Gen 3 keeps giving an error message and won’t operate. 
please help

[Jake]

Hey BatraD,

Sorry for the late reply. I wanted to follow up and ensure you are good to go. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further. 

Best regards,
Jake

[mth2000]

Jake, I have the same issue with an AprileAire 700 humidifier with the Nest Gen 3 thermostat.  All the documentation I have read indicates that the * and c will provide 24VAC to the humidifier to start it right up.  However, it doesn't work.  I measure 19VAC between * and c when the thermostat is calling for humidity.  I measure 14VAC when it's not.  I tried to install a relay but that doesn't work either.  It appears the * has almost no current to drive any load.  When I connect 24VAC from a transformer to the Aprilaire, it starts up without any issues.  I have also tried a different nest from somewhere else in the house in its place and get the exact same issue.  I am thinking this is a nest design problem?  I am at my wits end and looking for any help.