Hello everyone,

I came across this old thread but wasn't able to reply due to its age.

http://www.doityourself.com/forum/hu...-question.html

I want to eliminate the transformer as described in that thread, but have a question on how to close the loop. My furnace board has a HUM connection that supplies 24VAC.

My board here:


I follow all the other connections.
-Humidistat control H2 to Yellow1 on Humidifier.
-Yellow2 on Humidifier to Hum (24VAC) on furnace board

What do I do with Humidistat H1 that shows it's running to C on furnace control board? Is that C = Common? I have neutral terminals that I can use, but wanted to be sure before proceeding.



Thank you for your time!

 

I don't recommend using the G and Gf connections. The humidifier should only run when in heating mode to be most effective.

The C connection is available at the furnace in the same place the other thermostat wires are connected. C is not neutral..... it is 24vac common.

 

So I connect the humidifier control panel to C (where thermostat connects) twice? The left portion of the humidifier control panel is already connected to R and C. The two H for output then goes to the same C and the Hum on furnace board?

I will try without the G/Gf connections as you suggest since I am using cold water.

 

This is like what you're doing. Having some comp. trouble so I couldn't post it last night.

 

Wow, that's more simple than I imagined it to be. Wiring in this fashion will only turn on the humidifier when there is a call for heat correct?

Thank you!

 

How does the system work differently if I used the Hum terminal that provides 24VAC instead of the R?

I plan to use your wiring diagram, just wanted to understand.

 

Yes.... power (24v) on the W wire is what activates the automatic humidistat to turn on.

The HUM only becomes lives on a call for heat. You could use it to power the solenoid but not the humidistat. Using the R for all power only requires one wire.

If you were NOT using an automatic humidistat.... then you would need the HUM connection.

 

Thank you so much for your help. Everything is installed and wired up. It functions properly in the test mode. I'm glad I was able to install this without having to use the included transformer. One less part to break and the wiring was easier your way.

Thank you!

 

You're very welcome. Good job!

 

Hi all, new to the forum and didnt want to start a new thread since this one seems like it's exactly what I need. About to install an Aprilaire 400 to a Payne PG9M condensing furnace that I believe has the HUM option. If I am reading this correctly, I should wire up per post#4 without using the HUM option or the external transformer so that it only runs when it's heating for max efficiency. Ill post a new thread if thats preferred, but I think this is what I need to be doing. Thanks!

 

You can use the furnace for power. I like to use the separate 24vac transformer to run the solenoid but it is not critical.

If you are using an automatic humidistat.... you don't need the HUM connection.

 

Thanks Pete!

I would consider installing the 24 transformer if there were a benefit, otherwise I prefer to get out of the attic ASAP. Is this just a preference thing or is there some benefit to doing it that way?

 

It's not always known if the air handler/furnace uses a 24vac 40watt transformer. The worst that can happen is the smaller transformer fails from too much current draw and gets replaced with a larger one.

 

In my case, the PG9M specs indicate it has a 40va 24V transformer. If I understand correctly, 40va is the same as 40 watts, and I should be fine to run this entirely as you had posted with minimal wiring.

 

Yes... you are all set. V x A = watts

 

Thanks for being super awesome!

 

Hey Pete or anyone who knows.

Should this be in manual or automatic mode on the humidistat? Got everything completed today, and I when I was testing the solenoid didn't open up until I flipped the switch to manual mode. Maybe I was too impatient in my testing, so I figured I would ask, I wanted to get out of the attic as I was pretty tired of being up there, It's crawl room only. I do have the remote sensor run to the outside.

 

Just re-read my post. I meant I flipped the switch to blower activation mode from off to on. Tried again today, and it did not turn off when I flipped it back (while in test and with the heater running). I am guessing that the way I have it wired, it wouldn't really matter which way the switch was flipped anyway.

 

When you make a switch change..... you must turn power off to the humidistat and then back on to register the new setting.

 

Thanks for that info. I believe I did not power it off last night, I will have to test again.