Wiring an Aprilaire humidifier to a wood furnace blower?


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Old 03-21-16, 05:55 PM
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Wiring an Aprilaire humidifier to a wood furnace blower?

I have an Aprilaire 400 everything is installed correctly so far however the wiring instructions are for a gas furnace. I only have low, medium, high, and the common connection on my blower fan. The humidistat I'm using is an Aprilaire automatic digital control model 60 I know that I have to wire the humidifier transformer to the fan blower after that I am lost. I contacted my local HVAC guy but he was tooooo indepth in his instructions. I felt like I was back in Trig class in high school. I just need to know what wires go to what in laymans terms. I don't really need to know why it works. An example of what I need to know is: yellow wire from the humidifier goes to....... My humidifier has four wires coming out of it two yellow and two white, the two yellow come out of a small unit connected to the water line the two white come out out of the humidifier itself. One of the white and one of the yellow are twisted together from the factory with a wire cap. My wood furnace fan has high, low, and medium and a common. That is all I know. Can anyone tell me what wires go to what in simple terms. I just want the humidifier to turn on when the wood furnace fan does. The humidistat is mounted correctly but again, it has all these points of connection that I don't understand. If anyone can help me I would really appreciate it.
 
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Old 03-21-16, 06:33 PM
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I can help you out here.

First... a question.... what turns the blower fan on ?
You mentioned three speeds. Do you set it to a speed and it stays there or do you set it to a speed and a thermostat cycles it ?

We need to locate a 120v line that is thermostatically controlled so that the humidifier is not running when the fan is off. We can't just pick a motor speed hot line as there are three of them.
 
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Old 03-22-16, 04:44 PM
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Sorry I forgot to mention, I have a thermostat controlling a temp limiting switch which in turn controls my blower fan on the wood furnace. I have the fan set on medium. This is where I was planning on drawing my power for the transformer so my humidifier will turn on when the fan does. After that Im lost. I don't know what wires go to what.
 
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Old 03-22-16, 05:18 PM
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Ok..... good. We have a slight problem if you're going to use the model 60 automatic humidistat. It needs an always live source of 24vac and then a switched source to trigger the humidifier.

You could wire your 24v transformer so that it was always live and then use a 120v relay to activate the humidistat.
You could use a setup like this.... where a relay and the 24v transformer were mounted on a j box.

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If you were using a manual humidistat you wouldn't need the always live 24vac.
 
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Old 03-23-16, 04:08 AM
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So I would wire my transformer to the (out) side of the blower power and it will come on only when the blower turns on, and then purchase a 120v relay and wire it to the (in) live source of the blower so it has constant power? If I understood this correctly then where I go from here? (told you I was lost LOL)
 
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Old 03-23-16, 04:28 AM
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How do I wire my aprilaire humidifier to my wood furnace blower

I'm not very knowledgeable when it comes to wiring, the transformer reduces the power input, correct? Then would I also need another transformer for the constant source of power you mentioned to the humidistat??
 
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Old 03-23-16, 09:03 AM
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I will draw up a diagram for you if you decide to do it,.

You will need only one 24vac transformer to be connected to "always live" power to control the electronics in the automatic humidistat.

The relay will be controlled by the blower thermostat. Switched 120v gets sent to the relay. It will tell the humidistat that the blower is running.
 
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Old 03-24-16, 05:06 AM
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A diagram would be a big help, thanks.
 
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Old 03-26-16, 04:07 PM
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Hi, PJMAX Are you still there?
 
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Old 03-26-16, 05:27 PM
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Did you get the parts ? I need to know what relay you want to use.
 
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Old 03-27-16, 05:43 AM
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Sorry, I got ahead of myself, is there anything else I should know or do I just ask for a 120v relay?
 
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Old 03-27-16, 05:46 AM
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I forgot to ask, is there a way to wire the humidistat in a living space on the wall or does it have to me mounted in the duct?
 
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Old 03-27-16, 07:37 AM
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Mounting a humidistat in the living space is fine.

Here's your issue. If you used a manual humidistat there would only be two wires to the h'stat.
Since you're using an automatic one there will need to be at least four wires.

Any single pole or double throw relay with a 120vac coil will work. In the picture I posted is a RIB enclosed relay. I'd use the RIB-U1C. Functional-Devices-RIB-U1C-Relay-Box

I'll post a diagram later today for you.
 
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Old 03-27-16, 04:06 PM
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on the model 60 it has a sensor on the back how do I mount it so it will sense moisture. The rear mount is designed to be inserted into the duct. Would I have to frame it out from the wall?
 
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Old 03-27-16, 04:21 PM
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That's right.... I hadn't considered that. Yes.... it needs to have access to living space air.
 
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Old 03-28-16, 04:57 AM
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Im going to use neoprene spacers to bring to humidistat about 1/2 inch from the wall, will that be enough space for the sensor? and how far up the wall should it be mounted? I have ordered the relay you suggested, it should be here in a few days so I think Im ready for your wiring diagram.
 
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Old 04-04-16, 05:27 AM
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Hi, PJmax r u still there? I got the relay box you suggested, Im ready for your wiring diagram.
 
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Old 04-04-16, 12:19 PM
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Assuming you'll be using the setup I posted with the box.
You'll bring the orange and the yellow wire out of the box. The blue wire gets capped off.
The com = white/yellow and the 120v = white/black. Cap off - white/blue

Click on diagram for larger/hosted view.


At the box there is white for neutral. Black is always live and white/black is the thermostat output to the blower.

I'm showing four wires from your humidifier setup to the humidistat. That does not include the two wires needed for the outdoor sensor.... so keep that in mind. You can pickup 6 or 7 conductor thermostat cable and connect the sensor at the humidifier setup.

Somehow I assumed 700 humidifier. The wiring is the same as the 400 but the solenoid wires are yellow instead of brown and there is no 120v cord attached.
 
 

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