*Works great: **Fastly.Cool** and Warming environment perfectly controlled. I use 3 in different grow tents. It’s nice to see from your phone how your tent temps are. Does High and Low and records data.*

Thanks for positing this video. Great explanation, however this is not exactly how I did it. My Nest looks different than the one the presenter shows in his diagram. My Nest has a “C” terminal. I bought an Aprilaire 400 and tried to wire it to my Nest the way it’s described in this video. It didn’t work and after contacting Aprilaire, they explained the following: The 400 has two wires coming from it. One of those wires needs to connect directly to the C terminal on the furnace. The other wire connects to the * on the Nest. I was also instructed to connect another wire from the Nest’s C directly to the C terminal on the furnace. Once I did that, it worked perfectly. I also needed to replace the current 18/5 thermostat cable with an 18/7 for the extra cables. Hope this helps those of you that the same Nest I have. It’s a gen 2.

Awesome! I just connected my humidifier to my Nest 3 thermostat after waiting 2 years to find some reasonably straight forward instructions. Great explanation and a fantastic diagram.

I just got my old Chippewa 224 working after watching this. It was already installed when I bought the house in 2019 and I have no idea how long it has just been sitting and not running. I run the transformer must have been bad in it. I installed a Nest, bypassed the transformer, installed a new water solenoid just in case, and fired it up. Everything worked great!!!!

Hi Man... thank you so much. The logic is so simple, when people told me that I would have to replace my humidifier. And now it’s running normally again. You saved me a lot of money. Can’t express my gratitude enough.

Hi James you have explained every concept quiet well, I am confused at one point though. When we replace R wire to C terminal in traditional diagram where would the Second wire (C wire ) from humidifier will go ?

Really good video and clear explanation. I have followed this guide, having a 6-wire setup using Y1, G, OB, W2,C and Rh with an electric dual system. There is no extra wire that I could use for the C to *, so I tried different options - 1. tried to use the C wire to go thru the humidifier to the * connector, which caused the heating not to work and thee Nest would be in "delayed for 5min" loop. 2. tried to use the G wire to go from the C thru humidifier to the *, which would not turn the humidifier on. I have connected the humidifier directly on the HVAC from R to C to test if it works at all, which worked just fine. Any advice would be greatly appreciated. My last option is to replace the 18/6 wire with 18/8 wire, but that is a lot of work to fish the new wire. Thank you.

You are the sole reason I decided not to buy a Honewell stat and buy a Nest to connect a Dehumidifier. Thank you!

Excellent instructions..... Waited 2 years.... Going to try this today....

THANK YOU!! This saved me from spending $25 on a 24vac transformer. my bypass Humidifier is working great now!

Very helpful

I agree it will work without a relay but solenoids like motors cause current spikes and other noises on the line that could cause problems.. Also, a dead solenoid could theorically short the furnace's 24VAC transformer causing you to be in a bad situation at -20C! personally I'll go with a relay this way everything is isolated. an insurance policy of sort.

I’ve got Y1; W1; RH; G; and C hooked up to my existing Nest. I’ve got 3 unused wires that I have access to. What would be the easiest wiring to get done properly for me to hook up an Aprilair powered humidifier?

I’ve NEVER seen a humidifier wired up the way you have in the first schematic. It will continue to run if the humidity is too low, even if the blower isn’t running. You want the humidifier interlocked with a call for heat.

(New humidifier setup) If no other wires are available, and the 'C' wire at the Nest thermostat is already in use, can it be moved to the * ? Or will that mean it stops working for the furnace?

Hello , i have followed same wiring which you explained but the problem is nest doesn’t stop valve , if the fan is off , valve is open and water is on.

Please mention your name ! You did everything for me thanks lots love you.

Quick question. Would be great if you could shed some light on this. I’ve had the Nest Learning thermostat for about a year and I’m adding the Aprilaire 700. I have the same 5 wires you show on your diagram. The newer nest is a 10 wire terminal vs your 6 wires. When I installed the nest it had me install the common wire to the C terminal which isn’t on your diagram. I don’t have a wire running to the * terminal. Can I move the blue common wire to the * terminal. If I do this the humidifier kicks on but I’m worried the rest of the system won’t be working correctly.

To Better Understand....does the current/original C wire that goes from Nest to Furnace board stay on board, and add additional C from solenoid to C on furnace board. Or do you take off original C coming from nest?

Hey James, Would the * terminal on the nest only actuater the humidifier during the heat cycle vs fan only? Don't want to run humidifier during fan only cycles. Thanks Cliff

If I have a steam humidifier that takes longer to generate steam vs. a evaporator unit, will doing the steps you outlined in this video allow me to run my fan without calling for heat to disperse the steam throughout my home?

With the Nest would I be able to control BOTH a humidifier and dehumidifier? I have a Bos h heat pump that will not get my humidity below 57% in the summer and will be adding a whole house dehumidifier. I already have a humidifier in play for the winter months.

My humidifier has two yellow wires coming off the solenoid. To confirm, I attach a wire to the * port on my Nest 3rd gen and connect the other end to one of the yellow wires on the solenoid. I then connect the other yellow wire from the solenoid directly to the C terminal on my furnace board? I currently have a common wire which connects directly with the C terminal on the Nest to the C terminal on the furnace board.

So, does the C wire on the humidifer now connect where the R was? Then, is that all, or is a return wire needed. Total rookie with wiring here.

Question, I think I only have one humidifier wire in my current thermostat so would I just move that connection? It’s labelled as HM

Does the wiring dynamics change when the humidifier wiring runs through a 24v sensor switch?

Hi, thank you all your vids re Nest help a lot. One questions re (de) & humidifier wiring; since the humidistat controls the humidifier on/off sensing from return air, what function does connecting wires (to the * terminal) at the Nest help/do anything? What function does the Nest add/integrate with humidifier wiring to it, when the humidistat at the return is sensing the humidity level?? in other words, WHY do we send humidistat wiring to the Nest?

Hey, is the C that is coming to the humidistat from the furnace same as the C-Common that is needed for the Nest Thermostat? As I am missing C wire in nest thermostat and do not have a slot for the adapter like the one you showed in in your other video. I am not using the humidifier anymore so if I can use this C line to connect to my thermostat C that will solve my problem. Also is there a way to identify what is C and What is R on the humidistat?

Do you have a video on how to wire up a self powered humidifier to the nest?

I have a red wire and a black wire in the humidifire controller, do you know witch one goes to star connection in nest?

Do you know how to wire a Nest to a crawlspace dehumidifier? This would be a self-standing unit and a dedicated Nest just for this. I want this so I can adjust and monitor the dehum without having to crawl under the house. I have an AprilAire 1820 in the crawlspace. Thanks for any help.

What about the C terminal on the nest. Your not showing that.

Is there a way to hook up the humidifier to the nest on a four wire system?

Can you help me out I have a he300a humidifier how do I by pass the other connections

Why some people use a relay for the humidifier to the Nest? Your way seems way easier... Am I missing something?

would it work on a HRV?

(2020 Nest Learning Thermostat) Where does the second exposed wire for the humidifier that did not get inserted into the “*” terminal go (my old Honeywell thermostat had both wires connected to two U1 ports). R and C now on same terminal on furnace, but only R wire has designated place (*) on Nest. Do I connect this other exposed wire to the additional power (R) terminal on the Nest? Please help!!

Thank you James for the details. I have a nest e and furnace is already connected but it has only 2 wires for heat (w) and power(r). I add a common wire (c) using a 24volts transformer as you shown some of your videos. Now, I have aprilaire 500m humidifier that I want to connect on my nest e. What will i do if I don’t have a common wire(c) coming from my furnace? Thank you.

Great video. How would a zoned system work having 3 nest thermostats? Or can I only use one nest to control humidity? Or wire all 3 * wires through the humidifier. I have the aprilaire 800.

Thank you!!! but my question to you now is? in your previous video about NEST TSTAT it is well defined about wiring connections, here in this video it put my attention to "C" wire (common wire)! we should have a common wire connected to C terminal of tstat and c-board right? (based in your previous video), then adding another wire to (*) star terminal of tstat to power accesories like humidifier, does it mean the additional wire other end should be connected to c-board "c" wire as well? let say I have 18-7 wire, 5 of them is used most commonly R,C,Y,W &G, now adding another wire let say Brown color to (*) terminal of tstat, where is this brown other end gonna go? in the C-terminal of C-board? so two wire conected in the C-terminal of Control Board right? thanks

Why others show that you need a relay? Do I need it? I am trying to use my nest 3rd generation to control my aprilaire 800 series. Please advice.

what does this look like for the ECOBEE 4?

i have the nest e. it has a spot with a *OB on it. with that suffice as the star spot or do i need a 3rd gen neat or something? thank u great video

Will humidifier come on witout the heat being on? Will nest bring on blwer without the heat being on?

Thanks for the video!

Why are you using r,c you are making the humidifier operational all year long. It’s supposed to be only on heat

Do I need to use my humidifiers control unit if I’m using the best? Or can I get rid off it?

Hi James - few questions. First time messing with HVAC wiring so a lot of this is new to me: 1. I ran this configuration and I'm only getting 16v at my solenoid, and I believe it's too weak to open the valve. I did not run a common wire to my Nest and am using the R wire. Could it be that the R wire's 24v are being used to power nest and therefore don't have proper 24v across the Solenoid? 2. With this configuration I'm also seeing the 16v at solenoid even after I shutoff the "humidify" call on my Nest App. I would expect that to kill the * terminal and therefore kill all voltage. Why would I still be seeing voltage after killing *? 3. Have you run into any issues with this setup damaging equipment? It it possible to run an independent 24v transformer (Aprilaire provides) instead of power from R or C to power solenoid, with the * still being the switch?

Would you be interested in drawing a wiring diagram for me? I'm looking to hire someone who can tell me exactly which wire need to go where.

i don't see how to do this with an aprilaire model 800

Will this work with nest 2nd gen?

Why is the diagram in an angle? I had to rotate my screen by 30 degrees to be able to view the tutorial.

My humidifier is not working , ,

Can't see the diagram. Maybe edit this video and add a pic of the diagram.

What if your humidifier has two wires?

Wow, you shouldn't be wiring your humidistat by the "traditional" means shown here. If you do, you will run water without running the HVAC fan. DON'T DO THAT! Use a humidistat that will activate the fan when the blower is on, wire to the hum terminals on your furnace or wire in an Aprilaire model 50 current sensing relay per manufacturers directions. If you want to use the Aprilaire model 800 and want to control with a Nest you need to put a 24VAC relay in where he is showing the humidifier (wire the coil end there) the switching end should be wired to the humidistat terminals on the Model 800. It is a bad idea to put 24VAC on the humidistat terminals for the model 800.