Nest Thermostat - Whole Home Humidifier - No Humidifier Power Supply

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Old 10-30-12, 01:27 PM
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Nest Thermostat - Whole Home Humidifier - No Humidifier Power Supply

I found this post, which is very helpful if you have a separate power supply for the Humidifier. My furnace, a Bryant High Efficiency, has been set up with the power for the Humidifier being provided by the furnace.

I am only getting 16v from the Nest * wire when I set it up as a humidifier. There is NOT enough voltage coming from the Nest to trip the solenoid to turn on the water.

[ATTACH=CONFIG]4889[/ATTACH]

Can anyone tell me if I am doing things right or will I always need a relay with a separate 24v power supply??

Thanks,
Robert
 
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Last edited by rduchene; 10-30-12 at 01:53 PM.
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Old 10-30-12, 05:57 PM
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This is how it should be wired and you should use a relay the part number is in the picture. Just google it.
 
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Old 10-31-12, 01:44 PM
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Need advice on Nest and Whole Home Humidifier

This thread is very helpful but I have a question about hooking up your Nest without having a Relay.

When I hook up a wire to the * in the Nest and program it for Humidifier I get a couple of things.

1) The nest always says that no current was detected - not sure what that is supposed to mean. Gives an n29 error or something like that. Should I just ignore that error?

2) The wire ALWAYS has a 16v charge on it. I turn the humidifier control off - 16v - I turn the humidifier control on - 16v. I would think that the voltage would be nothing when the humidifier is turned off. Is there some setup I'm missing? The 16v is there if the furnace is heating or not, weather the fan is on or not.

Also I was wondering if you could bypass the relay and have Nest send enough voltage to trip the solenoid - attachment here.

Below are diagrams of what I currently have (on left) and what I would like to have - however the voltage coming from the Nest is not sufficient to trip the solenoid for the water.

[ATTACH=CONFIG]4919[/ATTACH]

Thanks,
Robert
 
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Old 10-31-12, 03:35 PM
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Hi, I moved your post from another thread back to YOUR thread. Please only reply here about your problem This is YOUR thread and so that no one gets confused please ONLY REPLY HERE.

I have answered your question with a diagram showing that you SHOULD use a relay and how to wire it. If you don't want to do it that way then it may not work as you already know because you are having problems.

In your picture on the right.... where is the gray line from the hum solenoid going to in the furnace? It should go to C on the control board and may be why you are not getting proper voltage. However, I really recommend using the relay and wiring as I have suggested.
 
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Old 10-31-12, 03:57 PM
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The grey wire going back is going to C - I just didn't show it correctly on the diagram.

The only other issue I'm having is that the * from my nest is constantly giving 16 volts - continuously - no matter what I set the thermostat for.

Not sure if there is some other setting i'm missing.

I'll look into the relay and try it that way. I discovered today that the folks that installed the new furnace left a 24 volt transformer that use to be used for the humidifier and then ran the humidifier through the furnace voltage. So I do have power just for the humidifier that is separate. Will try to find the relay and hook it up.

Still trying to discover how to make the nest send the proper signal.

Wish me luck!

Thanks,
Robert
 
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Old 10-31-12, 04:07 PM
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16V may be leak through voltage if it constantly gives that amount. Have you successfully changed the settings in your NEST to control the humidifier and turn it on with the nest? From what I have been told is that you MUST go into the advanced settings to determine how the * terminal functions. After you have set it up for a humidifier then you can changed it though the web portal and somehow get it from the actual thermostat. I am not willing to spend $250 on something that won't work with my system just so I can play with it and test it. Nest is fairly secretive on how it all works. At least they are fairly vague in the manuals they have released online.
 
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Old 11-29-12, 12:58 PM
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I had set the Advanced Functions - turned on the humidifier from the browser interface but still I keep getting 16v - don't know.
Still looking for the relay here in Toronto - not a big deal but wanting to get it done sometime!

Thanks for your advice.

Rbo
 
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Old 12-02-12, 07:56 AM
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I am using the relay circuit shown by hvactechfw, but had the same problem as rduchene-- voltage output on "*" terminal wasn't changing with Nest humidity control (14.9 VAC). Nest showed "humidifying " on display when it was supposed to, but wasn't changing the control voltage. Wonder if it might be floating at half of the transformer output voltage... Tried a reset on the Nest a few times without resolving the problem. Finally decided to exchange the thermostat for a replacement. New Nest worked perfectly, including humidifier.

Not sure what was causing the problem or if it could be corrected through software/firmware fix. I had been using the Nest without the humidify control for about a week until I could get the necessary relay. Thermostat had worked perfectly for my dual fuel heat pup/gas furnace, but when I tried to add humidifier control, ran into the output voltage problem.
 
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Old 02-25-13, 04:19 PM
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I hooked everything up as in the diagram

And I am having the same issue with 16V always coming from the nest. Is the only solution to exchange the nest?
 
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