Aprilaire 700 no voltage going to solenoid

Hello. I have problem with Aprilaire 700 humidifier. This unit is pretty old - it was already installed when I moved in to this house. I did some diagnostics and found the following:
1. There is power going to humidifier controller.
2. There are two wires going from control to humidifier. They have voltage. (26V)
3. There are two yellow wires coming out of humidifier. They never have any voltage. So solenoid will never open. I also verified that humidifier fan never comes on by marking one of the blade! And of course humidifier is plugged into 120V outlet. Verified that outlet is good. So seems like it is the humidifier that has problem. See two pictures.

Here are couple of things I am trying to figure out. One, to see if I am better of to replace the humidifier. If it is something simple, I'd hate to just throw it away. Secondly, if I am to replace it, I wonder if the newer/current Aprilaire 700 will fit the opening. And if wiring will be similar to what I have now. That will decide if I get it installed or if I can do it myself.

Thanks in advance.

 

Welcome to the forums.

Every company has built humidifiers with and without internal transformers. It has confused installers for years.

This is from my personal notes... PERTAINS TO ALMOND HOUSING…. PRE OCTOBER 2007.
The almond color power humidifiers have a 24 volt transformer built into the humidifier; therefore, they have their own power. To determine if the fan is working simply touch the two brown leads which extend out of the bottom of the humidifier together, while the humidifier cover is on and the humidifier is plugged into a powered outlet.

So if you touch the two brown wires together and nothing happens.... the internal transformer is likely bad. Be sure your unit is plugged into a live 120v receptacle.

 

Thank you Pete for quick reply. When I touch the two brown wires, I hear the fan turning and I do hear the click on solenoid. Maybe unrelated or separate problem. But don't think any water flows through. After the test, I unplugged the humidifier and checked the humidifier pad. The pad is not wet and no water in overflow.

I am sorry I am not sure what this tell me. The fact that fan is ok but humidifier is not supplying any power to solenoid when connected normally. Thanks again.

 

Ok..... so the internal transformer, relay and fan are good. Did you check for power to the two yellow wires while you had the brown ones shorted ? That's when the yellow wires should be live.

 

Sorry I forgot to note that. I did check and there is power to the two yellow wires. About 25V. I do hear the click on solenoid. I did remove the solenoid and cleaned it. Appeared to be fine. I am sure when I reconnected I connected it in right direction. Or else I think the screws don't line up. Also, because I was not totally finished tightening the nuts around solenoid, I could see very slight amount of water. So I know water is reaching the solenoid. Maybe some blockage after the solenoid or something wrong with solenoid.
Thank you!

 

I have an update on this. I have a correction to make on what I reported at beginning. I reported voltage on the H terminals - these are the wires wires going to humidifier (brown wires). But now I don't see any voltage at H terminals when furnace is on. I swear I observed voltage there. Maybe it was too much wine and & whiskey during holidays!

OK, I read lot of threads and Aprilaire 56 install instructions and manual. What I thought was light inside indicating power is actually diagnostic light. Based on manual (https://www.torrco.com/ASSETS/DOCUME...stallation.pdf) it looks like I need to replace the Aprilaire 56 controller. This light will not go off and wiring is fine. Here is what the manual says:

"9. Make sure the Red Diagnostic Light is not lit. If the Red Diagnostic Light is
lit, re-check your wiring. If the Red Diagnostic Light does not go off, replace
the Humidifier Control with a new unit."

Before I order Aprilaire 56 controller (about C$113), I will check the resistance at "OTD" labelled terminal. Again as per manual, resistance should be: (For Manual Operation, verify that resistance across the leads of Resistor Case is between 44,000 and 48,000 ohms.)

Thanks

 

On that h'stat.... the two H terminals are just a switch. The H terminals don't supply any power. Take the two wires off of H and measure them. If you see 24vAC on them...... it means the h'stat is calling for humidity by shorting the two H terminals.

If you don't measure 24vAC..... the problem is in the humidifier.

 

Ok, what happened was when you asked me to run a test by joining the two brown wires coming from humidifier, I had disconnected them from the Aprilaire 56 controller. So, yes there is no power at terminal H. And there is 26vAC at the brown wires coming from humidifier. I wrongly assumed power coming from controller. So my original info was correct. So humidifier seems fine.

Now with the diagnostic light constantly on while furnace is running, does it point to the Aprilaire 56 controller? BTW, I contacted couple of hvac guys. They want to replace the humidifier with new one and refuse to even attempt to repair it!
Thanks

 

Also, I remember in my previous house, when you rotate the humidistat switch (dial), you would hear a click. On this one I don't hear any click. But it was some other brand. I think it was Honeywell.

 

Just an update. I got new Aprilaire 56 humidifier controller. I connected it exact same way as my old controller was connected. It works fine now. The humidifier turns on, power goes to solenoid and there is water flowing!! So all along it was my humidifier controller that was bad and needed replacing. The new one did come with outside temperature sensor. But for now I just connected it as manual mode using the manual mode resistor that came with it. Later when I can figure out how to get the wire outside I will connect temperature sensor and run it in automatic mode.

Thanks for help.

 

Good job. If you have central A/C....... you may be able to follow the lines out thru the wall to where the outside condenser is located.

 

Thanks Pete. Yes, it's very odd that they give you two feet of wire to run it outside. That does not even make it to the wall! I am not really that technical with hvac stuff (I'm an IT guy!). I will have to get same gauge wire to run it outside. There are few criteria where thermostat can be.

In summary so it may help anyone else from spending C$500+ on new humidifier, if diagnostic light is on on humidistat, it's time to replace it. But still go through some tests as Pete suggested. Like joining the brown wires to see if humidifier is working.

Again. Thank you Pete! I hope to be able to participate if I can in helping others at this wonderful site - doityourself!

 

You can use any type of two conductor wire to extend.
Thermostat wiring is proper but even speaker wire will work.