Nest Thermostat Wiring With Aprilaire 600 + Humidistat

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Old 10-30-12, 12:03 PM
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Nest Thermostat Wiring With Aprilaire 600 + Humidistat

I have a Trane XC90 with an Aprilaire 600 humidifier that is connected to an Automatic Humidity Control dial. I have the (2nd gen) Nest hooked up to the furnace and all is well, but I would like to connect the humidifier to the * connector if possible. There is a transformer on the furnace that is connected to the 'R' and 'C' terminals of the humidistat, the humidifier solenoid connects to the 'H' terminals, an outdoor temperature sensor is connected to the 'ODT' terminals, and there are 'I+' and 'I-' terminals with nothing connected. How can I connect the Nest to this humidifier setup?
 
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Old 10-30-12, 07:19 PM
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Do both wires from the humidifier go to the H terminals on the humidistat? You will need a relay, I recommend a 6AZU2 relay. Google it. The transformer.... how is the primary side wired?
 
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Old 10-31-12, 04:01 PM
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I took some photos.. so here is the transformer:
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It is wired directly into the 'R' and 'C' terminals of the humidistat, seen here:
Humidistat
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The humidifier solenoid (here) is wired directly to the two 'H' terminals.
Solenoid
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How would the relay wire into the 'R' and 'C' terminals, exactly?
 
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Old 10-31-12, 04:40 PM
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Old 10-31-12, 06:10 PM
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Last question (I hope). When replacing my existing thermostat, I just wired up the Nest the same way. My thermostat did not have a 'C' connection, only 'R', 'Y', 'W', and 'G'. So I did not connect anything to the 'C' terminal of the Nest and it is working fine.

looking at your diagram, would it be okay to take the 'C' terminal of the humidistat and run it through the relay into the * terminal of the Nest, or do I need to split it off and connect it to the 'C' connector of the Nest as well as the * terminal?
 
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Old 10-31-12, 06:25 PM
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C does not have to be connected in most cases. If you have the wiring available I would wire it up but its not necessary.
 
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Old 11-02-12, 04:21 PM
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I think that this is a more accurate representation of my system, with the humidistat called out separately and attached to the transformer and solenoid directly. So is what I have in blue the correct spot to put the new relay?

Name:  Humidifier.jpg
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Old 11-02-12, 04:29 PM
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no, the nest is going to control your humidifier, you dont use the old humidistat anymore.
 
 

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