Aprilaire 865 + Nest 3.0

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Old 01-19-20, 09:09 PM
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Aprilaire 865 + Nest 3.0

Hello,

I recently installed the Aprilaire 865 (800 with fan pack). After several weeks of good operation, I decided to complete step two of my project, which involved replacing the Model 65 Humidity Control and fully integrating the humidifier with my nest 3.

I followed the setup described in the below thread using the 6AZU2 relay...
https://www.doityourself.com/forum/humidifiers-dehumidifiers/602330-aprilaire-800-nest-6azu2-help.html

One key difference / issue I have is that my boiler has an absolute rat's nest of wires and I'm struggling to find the C wire to connect back to the relay. Instead, I've tried to use the C wire from the wire harness provided with the fan pack (and was used when the humidifier was correctly working with the Model 65). I've connected it to the relay and the nest exactly as the above thread describes, just that it's coming from the humidifier / wire harness instead of my furnace.

So far, I'm having no luck as the nest keeps throwing an error code...I'm guessing there is a reason no one has recommended using the C wire from the humidifier previously, but hoping someone can give me some pointers as to why that doesn't work. Below is the diagram from the Fan Pack installation guidelines that talks a bit more about the wire harness / C wire.

Any help / thoughts is greatly appreciated!

https://www.doityourself.com/forum/a...1&d=1579492921
 
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Old 01-19-20, 09:17 PM
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Welcome to the forums.

There is no C connection "from" the humidifier.
You said boiler..... is that a mistake ? Should be a furnace and hot air.

Your 800 has two wires that go to the humidistat. They are labeled H and H. A direct short on those two wires makes your humidifier operate. In order to have the nest run it...... you will need a 24vAC relay. The two HH wires go to the switch part of the relay. The coil of the relay connects to * and C at the furnace.

Your furnace should have a control board where the thermostat wiring connects. That is where the C needs to come from. This board may be down in the blower section of the furnace.


 
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Old 01-19-20, 09:39 PM
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Thanks for the quick reply PJ.

I have a steam boiler. The 800 has a retro fit kit, called the 865, that involves installing insulated copper pipe to an installable vent called a fan pack for those of us that don't have central air.

As part of that kit, they provide a wire harness (see earlier diagram) that creates a splice point for the C and R wires used on the model 65 humidity control. I guess I'm confused why / how the model 65 is powered if isn't truly a C wire?
 
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Old 01-19-20, 09:55 PM
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Ahhhh.....ok. I see how you're using the 800.

The C on the humidifier is just for local control. The relay is needed to integrate the humidifier with the nest.

So you have a steam boiler with only one thermostat..... correct ?
Does the nest also control any A/C system ?
When you mix an A/C system and a boiler.... the C comes from the A/C system.
 
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Old 01-20-20, 09:06 AM
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PJ--I only have one nest 3 thermostat that I'm trying to use to control both the boiler and aprilaire 865. We do not have an AC system.

See attached diagram for how I have it wired up right now--it may not be easy to follow so let me know if you have any questions. My assumption that the white is a C Wire is based on the labeling in the model 65 control (which was hooked up and working previously to my attempts to integrate with the nest). I've also attached an image so you can see the inside of the model 65 from when it was previously hooked up.
 
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Last edited by TimTaylor122; 01-20-20 at 10:55 AM.
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Old 01-20-20, 06:55 PM
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Ok..... I need to see what/where the thermostat is connected to at the boiler.
The C wire must be referenced to R and W...... that means C must be obtained at the boiler.

 
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Old 01-20-20, 07:51 PM
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Due to the rat's nest of wires I am having trouble following everything, but wanted to provide the attached diagrams from the owner's manual that the installer left behind. I have verified that the low water cutoff referenced in the attached diagrams is the same that is on my boiler--so the actual wiring should hopefully match these diagrams.
 
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Old 01-20-20, 08:50 PM
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Ok..... labeled your print.

You must connect the thermostat wires as listed below. When there are only two wires..... R and W have no polarity. Now with the addition of C..... polarity is critical. I don't know what color wires you are using but make sure the nest letter matches the boiler color.


R of nest connects to blue splice in boiler.
W of nest connects to brown wire in boiler.
C is the yellow splice.

If you have a spare wire..... connect C to the nest also.

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Old 01-25-20, 09:33 AM
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Hi PJ--had a crazy week at work so just getting back to this....

I followed your diagram but am getting a no power to C wire error on the nest. I ran a new wire from the 5 yellow wire splice point (actual wiring appears to follow install diagram). I put a voltage tester on it and am getting nothing. Also tested all 5 yellow wires and nothing on those as well, even with the boiler running.

Note that I also disconnected everything humidifier related to the Nest when trying to just get the C wire from boiler functioning. So all I have plugged into the nest is W, Rh, and C.
 
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