Nest and HE-240 Honeywell humidifier

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  #1  
Old 08-09-16, 02:53 PM
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Nest and HE-240 Honeywell humidifier

Hello. I am glad I came across this post as I have just purchased a Nest and have the same humidifier as the poster (Honeywell HE240). Hopefully some of you will still receive alerts about new comments.

As I started to try to connect my furnace, AC, and humidifier to the Nest, I found that the current thermostat were only about 22 or 24 gauge and stranded, so I bought new solid 18 AWG and pulled it up from the furnace to the location of the thermostat. I have since started to connect wires to the Nest base plate, but have some questions re connecting the humidifier.

For your reference, I have attached the Honeywell wiring diagram.

Current Humidifier Set Up
Rather than using the 24V transformer, the previous home owner (a certified electrician) connected the solenoid wires to the furnace HVAC board's C and W terminals. I understand this as the humidifier would only ever need power when the furnace is on (the only time we use it where we live). He then connected the humidistat as per the wiring diagram.

What I have done so far
  1. I connected the two blue wires together for the pressure switch, to close the circuit
  2. I connected one of my newly pulled wires to the Nest's * terminal
  3. I connected the rest of the wires for the furnace/AC/Nest (W1, Y1, RH, and G, and C) as per Nest's "Conventional 1 stage heating and 1 stage cooling" instructions in the Pro Installation & configuration guide that I found on their website.

Now what I am wondering is, if I just connect one of the humidifier wires to the Nest's * terminal and the other to C on the HVAC, will I also need to either:
  1. Buy a 24V transformer (I can't find the original one); or
  2. Just leave the humidifer as it is (one wire to the furnace C post and one to the W)?

I am kind of thinking that, yes, I will need to give the humidifier power from somewhere as the Nest will now only act has the humidistat?

I hope I have articulated this well enough. Thanks in advance to anyone listening!

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Last edited by PJmax; 08-09-16 at 03:33 PM. Reason: started new thread
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Old 08-09-16, 03:13 PM
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I supposed that, if I do need a transformer, this one should work just fine?

https://www.lowes.ca/humidifiers/wai..._g2540940.html
 
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Old 08-09-16, 03:37 PM
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Welcome to the forums and your own brand new thread.

You will not need a transformer.
The * terminal is a 24vac output when the stat is calling for humidity.

You connect one wire of the water solenoid to system C.
The other wire from the water solenoid goes to Nest *.

The nest can be programmed to turn on the blower and humidifier when the humidity is low
OR
My choice... humidify only with the heat running. This option allows for the most moisture transfer and least amount of water wasted.
 
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Old 08-09-16, 03:51 PM
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Thanks, PJmax. This helps clarify a few things for me (and saves me a trip to Lowe's through rush-hour traffic!)

So, I was mistaken to think that I could configure the Nest to turn on the humidifier only when the following two conditions were true:
1. the heat was on; and
2. when the humidity level was below my desired setting?

If I set it to HEAT + HUM on the Nest, the humidity will stay on constantly while the heat is on? My only concern with this is how much humidity there will actually be if it is really cold here in the winter and my heat is on a lot? As you stated about, the alternative is that the blower would come on with the humidifier when it gets below my desired setting? Therefore, in theory the heat could have been on for a while to bring the temperature to my desired setting and then once it turns off, the blower + humidifier may come on right after the heat is one to bring up the humidity?
 
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Old 08-09-16, 04:00 PM
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So, I was mistaken to think that I could configure the Nest to turn on the humidifier only when the following two conditions were true:
1. the heat was on; and
2. when the humidity level was below my desired setting?
You are not mistaken..... this is correct.

The humidifier will only operate when the heat is on and when humidity is below the setpoint.
 
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Old 08-09-16, 04:02 PM
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Right on. Thank you. I will finish connecting everything tonight and report back.
 
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Old 08-09-16, 05:26 PM
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Does it matter which wire's I connect to the Nest * and furnace C? (Red or white?)
 
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Old 08-09-16, 08:56 PM
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Since you are working with 24vAC..... there is no polarity.
 
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Old 08-09-16, 10:28 PM
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Wait, you mean DC, correct?

I got everything hooked up. I ran the the tests and everything appears to be working fine.

Do you know much about the equipment settings? I have a single-stage heating system. In SETTING > EQUIPMENT > PRO SETUP, my W1 says:
- Heat
- Gas
- Forced Air
- Don't activate fan

But my * says:
- Humidifier
- Hum. + heat
- Activate fan

When I push the Nest to get to the first settings screen and to go FAN, it is set to AUTOMATIC. Why would my W1/Heat say"Don't activate fan", but my */Humidifier say "Activate Fan"?

Perhaps I am misunderstanding the fan setting here and it means,
"Activate the humidifier when the fan is active"?

My settings: https://goo.gl/photos/5wEnwYQTH3NutEmx8
 
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Old 08-10-16, 12:15 AM
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NO..... I mean AC. The system is 24vac.

Looks ok.

The furnace activates the fan in W1 mode.
You may have no choice in the Hum+heat mode. Will be ok as them hun can only work in heating.
 
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Old 05-16-17, 09:22 PM
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7 months later

Been about 7 months and everything still working fine. Thanks again!
 
  #12  
Old 05-16-17, 10:37 PM
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Great news. Always appreciate a return visit.
 
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