1-Wire/2-Wire Humidifier - Nest Install


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Old 04-28-18, 05:48 AM
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1-Wire/2-Wire Humidifier - Nest Install

Apologies in advance if this is a silly question or if it's already been answered, but what truly is the difference between a one wire Humidifier and a two wire Humidifier? Is it as simple as how many wires go to the humidistat or does it mean something else?

I ask because I'd like to install a Nest Gen 3 thermostat to replace my current thermostat/humidistat setup. I have a Carrier bypass humidifier that has two terminals (also have a Carrier furnace). Do I need to install a relay? If not, what do I do with each wire (one to Nest, the other?)?

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FYI - I've looked through the forums (great work here, all... good stuff) and don't know if my solution is already out there or not. This seems to be similar but not sure - https://www.doityourself.com/forum/h...midifiers-130/

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Thank you!
 
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Old 04-28-18, 06:06 AM
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Technically they are both 2 wire humidistats. One wire is power supply and the other is signal to humidifier.
 
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Old 04-28-18, 09:39 AM
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Welcome to the forums.

The nest is a one wire connection.
One wire from the humidifier goes to the *.
The other wire goes to C on the furnace/air handler.

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There is nothing else in the line. The old humidistat gets removed or bypassed.
 
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Old 04-28-18, 10:06 AM
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There is a difference.

A 2 wire model likely has it’s own transformer.

If your humidifier has its own transformer you will probably need to install an isolating relay before you can connect it to a Nest.

What is the model number of your humidifier?
 
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Old 04-28-18, 12:42 PM
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Thanks all for the quick responses! Very much appreciated.

The humidifier is a Carrier HUMCCLBP2417-A--

It looks like the humidifier just has one wire (red/white) that goes into and out of the solenoid. The red wire connects to the HUM terminal of the furnace and the white wire attaches to the Com 24V terminal. Based on PJMax's comment would I simple keep the white wire connected to the Com and connect the other end of the white wire to the * on the nest (and just completely disconnect the red wire)? I don't see a separate transformer for the hum. Thanks!
 
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Old 04-28-18, 12:59 PM
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Some humidifiers plug into 120vac and have an internal transformer inside them.
Yours does not and is a standard 24vac bypass humidifier.

Correct on the wiring.
 
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Old 02-02-19, 03:45 PM
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Hi all,

I wonder if you wouldn't mind taking a look at the attached diagram? I am guessing this is a 2-wire humidifier. That being the case, would I put the relay in line with the very bottom wire (diagram) coming out of the transformer?

The control for the humidifier has 6 wires connected to it. 2 wires go to the solenoid, 2 wires go to the outside thermister, and 2 wires are the input power (24vac).

I hope the diagram attaches properly.

thanks


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Old 02-02-19, 03:50 PM
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Welcome to the forums.

I will be making this its own thread.

The diagram you've posted does not reflect an automatic humidistat.
That is a manual stat and current sense relay system.

Please post the make and model of what you are working with.
 
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Old 02-02-19, 04:40 PM
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Hi,

Sorry, I should have included this information in my original post.

This is a Lennox WB2-17A
 
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Old 02-02-19, 09:57 PM
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A couple observations on my setup (Lennox WB2-17A).

Power to the humidistat control energizes when the blower starts up. This apparently as a result of the current sensing relay. I'd like to put a relay on this power supply to tie the nest to the solenoid. And then I'd like to remove the entire humidistat control and patch the hole in the air duct.

Is this the correct approach?
 
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Old 02-03-19, 10:28 AM
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I am assuming that this is the humidifier model that does not plug into a 120v receptacle.

You can do one of two things..... use that transformer and a relay or do away with the transformer and just let the nest run the humidifier.
 
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Old 02-05-19, 06:29 AM
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This ended up working out perfectly. I used a White Rodgers relay as per recommended by nest. I completely removed the humidistat from my system.

For those that have this type of humidifier, the power to the humidistat is supplied only when the blower is running. I wired this power into the relay/solenoid and covered the hole left by the humidistat with silver tape.
 
 

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