New Aprilaire 700M

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Old 11-12-10, 08:40 PM
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New Aprilaire 700M

Hello. I purchased an Aprilaire 700m to replace an existing Aprilaire 760, and I want to make sure I wire the humidifer control properly. The current 760 has three separate wires going in (6 total connections) - 2 connections from the furnace (24V), 2 connections for the outdoor temperature sensor, and 2 connections labeled "A/A", that connect to the humidifier. The control for the 700m has only 2 terminals for connections. Which wires go where?
 
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Old 11-12-10, 08:50 PM
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Is the old humidistat still working? If so, you can keep that one instead of the basic model.

What was wrong with the old one?
 
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Old 11-13-10, 05:51 AM
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The motor started going on the old one. The old one was the original, and for an extra $100, I could get a new one.
 
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Old 11-13-10, 10:48 AM
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I believe the old humidistat works. I actually have that one hooked up now to the new humidifier, but it doesn't seem that it is powering the humidifier. I've run the furnace in heat mode, and I don't see the fan running on the humidifier.
 
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Old 11-13-10, 11:33 AM
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I hooked up the new humidistat. I tried the furnace in heat mode and the furnace works, but the humidifier isn't kicking on. I took the red 24V wire from the furnace and connected it to one terminal in the humidistat, and the red wire from the humidifier and connected that to the other terminal in the humidistat. I connected both white wires to each other.
 
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Old 11-13-10, 03:13 PM
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With the old humidistat, make sure the mode switch is set to "Power Humidifiers".

R goes to 24 volts power
C goes to common

Two wires from the humidifier goes to H

I am guessing the other two is going to the outdoor sensor? If so, what is the temps outside?
 
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Old 11-14-10, 08:11 AM
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aprilaire 700m

The temp yesterday was in the 50s. With the old humidifier, it seemed to go on every time the furnace would come on in heat mode. With the new one, I'm guessing it's only going on when the humidity level is below what's set. I did get the new humidistat connected. Do you know if there's a way to test the 700m to verify that the humidifier is actually working, without waiting for the humidity level to get below the setting?

I had the old humidistat hooked up with the new humidifier. I didn't change any of the connections in the old humidistat - I just connected the two wires from the old humidistat to the new humidifier. I tried the test mode, but I don't think it turned the humidifer on. It's possible the old humidistat wasn't working as expected.
 

Last edited by steres; 11-14-10 at 08:31 AM. Reason: additional information
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Old 11-14-10, 09:43 AM
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Was the switch set to "Powered"?

Take the two wire from the humidifier, and short it together and see if the humidifier turns on.
 
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Old 11-14-10, 06:42 PM
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There isn't a "powered" switch on the old humidistat. Basically, it looks like the new one, except there is a "test" setting at the end of the dial.

I'll try shorting the two wires together and I'll let you know what happens.
 
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Old 11-14-10, 07:04 PM
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I took the two wires off of the terminals in the humidistat and touched them together. I got nothing. When I have the humidistat connected with the two wires, I can turn the dial (at this point, I go to about 40%) and I can hear the click. But, I get nothing out of the humidifier.
 
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Old 11-14-10, 08:55 PM
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What was the power source for the old humidistat? (R and C)
 
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Old 11-15-10, 11:52 AM
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the power source for the old humidistat was the furnace motor. Of course, after I submitted my last reply, I realized that I probably need to have the furnace running in heat mode before shorting the two wires together. That'll be the next thing I try.

But, I originally kept all of the connections in the old humidistat, and connected that to the new humidifier, and I still wasn't getting the humidifier to turn on.
 
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Old 11-15-10, 09:31 PM
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Originally Posted by steres View Post
the power source for the old humidistat was the furnace motor.
Huh? Was it piggy back on one of the fan speed, and a transformer is used?
 
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Old 11-16-10, 07:01 AM
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I believe a transformer was used. Of course, it's attached to the furnace motor outside, so I can't really see exactly what it is (it was there when we bought the house).
 
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Old 11-16-10, 11:38 AM
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This how you wire it to the transformer.

 
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Old 11-18-10, 07:27 PM
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That's the picture I've been looking for. Actually, that's how I have it wired, and it still doesn't work. I also tried wiring the furnace and humidifier directly (without the humidistat), and it still wasn't turning on. I tried all the combinations. Is it possible that the solenoid is bad?
 
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Old 11-19-10, 06:52 AM
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Do you have a meter to see if you got 24 volts at the valve?

If you got power at the two wires then check to make sure you got water going to it. If all checks out then yes, you may have a bad valve.
 
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Old 11-19-10, 03:16 PM
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I have a small volt meter, and I seem to be getting power from the two wires. My next step, I think, is to swap out the new solenoid with the old one from the 760 model.
 
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Old 11-19-10, 03:41 PM
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"Seems'? What voltage reading are you getting?
 
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Old 11-19-10, 06:10 PM
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Sorry - I just have a simple voltage meter that doesn't tell me the exact voltage I'm getting. That may be my first trip tomorrow - to get a voltage meter that tells me that. At this point, I'm also going to reach out to Aprilaire to find out what they suggest.
 
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Old 11-19-10, 09:10 PM
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Just need to get a meter to see if we are getting 24 volts. If we are, then we know the coil may be bad then.
 
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Old 11-20-10, 01:17 PM
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So, I got a meter, and it didn't seem to be registering anything. I'm wondering if I knocked something else out.
 
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Old 11-20-10, 08:57 PM
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Did you try taking a reading on the two screws on the transformer? (Make sure the furnace is running)
 
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Old 11-23-10, 02:08 PM
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I did. I wasn't getting anything. Turned out that, when I first wired it, I must have done something and blown the transformer. I wasn't too sure of myself to fix it, so I called my local HVAC guy who came out and confirmed my suspicion. He replaced the transformer and everything is working. Thanks so much for your help!
 
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Old 11-23-10, 02:18 PM
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Wish you could of hang in here longer and would of figured it out. But at least you are up and running again.
 
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Old 11-23-10, 07:03 PM
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Thanks. I actually had it pegged as a blown transformer, but, with me being a newbie at this, I didn't want to take the chance and end up blowing out my entire furnace.
 
 

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