Humidifier / Nest / Furnace Control Board


  #1  
Old 12-29-20, 04:15 PM
M
Member
Thread Starter
Join Date: Dec 2020
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
Humidifier / Nest / Furnace Control Board

I've skimmed through a bunch of posts and have probably already seen my answer, but wanted to start a new thread to clarify.

I have a new HVAC system (Thermal Zone gas something or other), and the Nest Gen 3, and have just installed an AprilAire 400M. HVAC has all been working fine for a year and I'm just now getting around to the humidifier. The three products have conflicting directions for wiring.

The * from the Nest connects (orange wire) to the Humidity input on the furnace with all the other inputs. Then, there are two HUM terminals on the other side of the board. The instructions say dry contacts. What is the likelihood that I can connect the two wires from the humidifier directly to these terminals and the solenoid valve will open then the nest calls for humidity and the furnace calls for heat & fan?
 
  #2  
Old 12-29-20, 05:24 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,929
Received 3,950 Upvotes on 3,543 Posts
Welcome to the forums.

Starting a new thread is always appropriate.

Not sure what type of board that is.
You could post the part number off it or a picture of it..... How-to-insert-pictures.

Here's what you need to do......
Connect one wire from the humidifier to the C terminal.
Connect the other humidifier wire to one of the HUM terminals.
Connect the other HUM terminal to the R terminal with a short piece of wire.
The HUM terminals will now switch 24v to the humidifier.
Since this is AC.... there is no polarity on the HUM terminals or the solenoid.
 
  #3  
Old 12-29-20, 08:04 PM
M
Member
Thread Starter
Join Date: Dec 2020
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
Currently I have one wire from the humidifier connected to COM and the other to HUM STAT on the terminal from * on the nest. This allows the fan to run and the water solenoid to open whenever the humidity level is below the set point with or without heat. Unfortunately this is inefficient and I would rather have the solenoid open when both the heat is below set point AND humidity is below set point. Fortunately the 400M is efficient with water use and hasn’t wasted a drop.





 
  #4  
Old 12-29-20, 08:28 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,929
Received 3,950 Upvotes on 3,543 Posts
I see the white wire from the humidifier on the HUM stat terminal along with a black wire which is probably the * wire. I don't see any orange wire connected.

Where is the red wire from the humidifier connected ?
That terminal strip is not on the wiring diagram.
 
  #5  
Old 12-29-20, 08:34 PM
M
Member
Thread Starter
Join Date: Dec 2020
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
I noticed that too. The actual board does not line up with the figure. The black (from thermostat *) and white from humidifier are both on the hum stat terminal. Red from humidifier is on COM which is next to two accessory terminals. I checked voltage while playing with the nest app and there’s 28V only when it calls for humidity and will run the fan.

Also correct, it was black and not orange. I might still have orange available as I ran an 8 wire cable.
​​​​​​
 
  #6  
Old 12-29-20, 09:04 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,929
Received 3,950 Upvotes on 3,543 Posts
So the nest is directly controlling the humidifier. It's not being switched thru the hum terminals.
That should be ok...... or you could make a wiring change.

 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: