Aprilaire 500a humidifier wiring

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Old 02-09-10, 09:02 AM
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Aprilaire 500a humidifier wiring

I searched these forums, but couldn't find (or understand others) what I need on how to wire my Aprilaire 500a humidifier. I have a new house which has of course a new gas forced air furnace as of July 2009 (sorry, I don't have the furnace brand off hand).
Since I also have an ERV air exchange system running, I want to run the humidifier during the blower call (not during heat call)
I have two wiring issues. *Note I have the Aprilaire 500a with digital control and a transformer that came with it*

1) One problem I'm having is understanding how to wire the R & C from the humidistat to the furnance for constant power. In the Aprilaire diagrams, it shows wiring to the 24V transformer and that to nothing. I assume the 24v trans needs to be wired somewhere. Also, my furnace has the R, C, Y, W, G? terminal and I believe it already is 24v, but not sure. Can I just wire the R, C on the humidistat straight to the R, C on the furnace board?

2)Also, how do I wire the W/G & Cf on the humidistat? Do I use the transformer supplied for that? Since I'm going to run the humidifier during blower call, do I run the W/G to the EAC, and Cf to where?

Thanks
 
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Old 02-10-10, 06:39 AM
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I am going to need know the model # and brand of your furnace so we can hook this up right.

ALso, from my experince, I find that running the humidifier with fan only did not do a good job, and lead to wasted water. I switched it over to heat only, and it keeps up just fine, and less "on' time.

Is your HRV running all times or what?
 
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Old 02-10-10, 06:49 PM
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Originally Posted by Jay11J View Post
I am going to need know the model # and brand of your furnace so we can hook this up right.

ALso, from my experince, I find that running the humidifier with fan only did not do a good job, and lead to wasted water. I switched it over to heat only, and it keeps up just fine, and less "on' time.

Is your HRV running all times or what?
My furnace is a Nordyne 072C-12A. I have my air exchange system (Renewaire br130) running at 70% of the time.
Here is a picture of the furnace board diagram:
http://img690.imageshack.us/img690/3...rnaceboard.jpg

Thanks
 
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Old 02-10-10, 08:49 PM
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70% of the time is a lot. You don't need it to run that much, and that much of run time will dry out the house, and the poor humidifier is going to be working over time.

What kind of control are you using for this HRV? The ones I've seen has on 20, off 40., I'd suggest setting it to this if your home is new.
 
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Old 02-10-10, 10:40 PM
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The control for this is a percentage from 0 to 100% which goes off the fan call.
I turned it down to 50% to see how that works. My total square footage of the house is 2068, so I was going by the manual's recomendation. Were you able to determine the correct wiring for this? I just finished installing the humidifier and all connection except the wiring.

Thanks again!
 

Last edited by ryanjp; 02-10-10 at 10:57 PM.
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Old 02-11-10, 05:33 AM
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Try 50% but if it still dries out the home and the humidifier is working over time, then I'd go down to 30 or 20%. Does your control have a humidity control as well for the HRV?

As for hook up, wire the transformer to HUM (You can do EAC if you want to). Then the low voltage from the transfromer goes to W/G, and Cf.

Then R and C goes to R and C on the furnace.
 
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Old 02-11-10, 07:17 AM
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Originally Posted by Jay11J View Post
Try 50% but if it still dries out the home and the humidifier is working over time, then I'd go down to 30 or 20%. Does your control have a humidity control as well for the HRV?

As for hook up, wire the transformer to HUM (You can do EAC if you want to). Then the low voltage from the transfromer goes to W/G, and Cf.

Then R and C goes to R and C on the furnace.
So, do I wire the W/G and Cf on the humidistat control to the transformer (which has two screws), then the black and white wires on the transformer with one going to the HUM and the other to a neutral (you say transformer to HUM, sounds like both wires or something). Can you tell me which one via the picture diagram I provided in a previous post?
Also, I assume I need to crimp one of the wires on the transformer to the special connection pin to connect on the HUM?

Sorry, I almost need a diagram explaination, step by step.
 

Last edited by ryanjp; 02-11-10 at 08:18 AM.
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Old 02-11-10, 11:42 AM
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Also, I assume I need to crimp one of the wires on the transformer to the special connection pin to connect on the HUM?
You'll need a 1/4" female spade, and yes crimp that on to the wire and slide it over the made spade.

Sorry, I almost need a diagram explaination, step by step.
Here's an old drawing.

 
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Old 02-11-10, 01:33 PM
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Thanks a lot Jay! Can my common on from the transformer also go to the C terminal on the furnace control board? The reason why I ask is because all 3 common leads (via spade connections) are taken up next to the HUM and EAC spade terminals.
Also, on my transformer, the screws are labels 24Vac and 10A or something like that, which is which? I can't tell which is hot and neutral.

Thanks again.
 

Last edited by ryanjp; 02-11-10 at 01:49 PM.
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Old 02-11-10, 04:44 PM
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Originally Posted by ryanjp View Post
Can my common on from the transformer also go to the C terminal on the furnace control board?
No, the neutral/common on the line voltage side of the transformer goes to the HUM/EAC neutral spade on the board.

Also, on my transformer, the screws are labels 24Vac and 10A or something like that, which is which? I can't tell which is hot and neutral.
It won't matter on low voltage of what screw is hot or common.
 
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Old 02-11-10, 05:16 PM
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Originally Posted by Jay11J View Post
No, the neutral/common on the line voltage side of the transformer goes to the HUM/EAC neutral spade on the board.

Ahhh, now I see, my board has a HUM on the bottom middle, and on the bottom left is for all the neutrals. Makes sense now. I will do this within an hour and update.
Thanks for all your help!
 
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Old 02-11-10, 10:33 PM
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My humidifier is not running. The humistat is on, and in mode A and turned to the highest setting, it reads RH of 34%. The saddle valve is open and water goes to the selenoid, but it doesn't run past there (no water goes to the inside the humidifier.
One thing that worries me is after I got all done wiring, I turned the circuit breaker back on and I heard a pop and smoke at the furnace control board and the circuit breaker tripped (never good). I noticed I didn't plug the 6 prong inducer/ignitor connector (see my picture in above post, it's very bottom left on control board). I plugged it back in and switched the breaker on and the furnace started up normally with heat and all. But the humidifier still does not run.
What could be going on? Did the pop sound and smoke signal the wiring was wrong? No fuse is blown and everything looked fine but I still noticed a slight burnt smell, can wire get fried?
 

Last edited by ryanjp; 02-11-10 at 10:56 PM.
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Old 02-12-10, 11:59 AM
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Also, I just pulled the transformer out and pretty much confirmed that was what blew. It still lingers a little of the burnt smell. That's why I was cutious on how to wire that correctly. The wires must have to be wired specificly, the transformer doesn't say which screw cordinates with the hot or common. Looks like I'll have to get a HVAC person over plus an extra charge for a new transformer.
 
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Old 02-12-10, 03:04 PM
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Well, the HVAC person came and along with confirming the burnt out transformer, noticed the connection on the humidistat melted that whole part it was connected to. He then quoted replacing that for $150 or a manual humidistat for $50. I just bought this thing and not to happy right now. So basically, I have a dead humidifier sitting there and will probably get billed anywhere from $50-100 just for the basic service charge, and now will have to at least spend more to replace the humidistat along with paying them to do the job right. This picked a bad time for this to happen.
 
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Old 02-13-10, 06:05 AM
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I don't understand how it burned the transformer?

You had the black wire from the transformer to HUM 120v?

Then white wire to one of the neutral slot?

The low voltage screws don't matter on a low voltage.

What wire were burned on the humidistat?
 
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Old 02-13-10, 07:33 AM
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Yes, I had the black wire on the HUM 120v and the white on the neutral slot. I'm a little confused by the low voltage screws, aren't they the ones mounted inside the furnace side, and according to the picture you supplied above be the high voltage? I've seen other actual taken pictures with the transformer mounted this way, and I know it even says to be mounted inside the furnace which puts the screw side inside. Now by looking at your picture above, it seems you have it the other way, should I have done that?

On the humidistat, what burned off was a blue flat knob that came off it's contacts, if that's only what happened I can solder it back on and see if it works. I'm sure the HVAC person was trying to sell what they have.
 
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Old 02-13-10, 09:47 AM
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Take a photo on how the wires were hooked up.

here is a photo of my transformer.




Note. my line voltage is hooked up behind the cover, then the low voltage wire are on the screws.
 
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Old 02-13-10, 05:41 PM
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The way it looks in your picture, the low voltage from the screws go to the furnace board (since it's inside the furnace), opposite of what the diagram above shows.
I think what I did was\I had the transformer reversed.
 

Last edited by ryanjp; 02-13-10 at 06:11 PM.
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Old 02-13-10, 08:17 PM
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No, the low voltage (screws) is not going to the board, it's going to the humidifier control.

The wire behind the box that the transformer is mounted is going to the board HUM 120 volt hook up.
 
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Old 02-15-10, 08:46 AM
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Would it work to wire the W/G, Cf on the humidistat to the W, and C on the furance board strip? It shows it that way in a wiring diagram as an option also during heat call. Though I tried this and it blew the 3 amp fuse in the furnace, which then I replaced. I'm having a terrible time with this. I also tried wiring the transformer, the right way, and nothing happened, but the transformer got really hot, it the transfomer dead? I'm at a loss???
 
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Old 02-15-10, 08:03 PM
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Did you get a new humidistat?

YOu could wire to the board, but may be too much for it.
 
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Old 02-16-10, 09:01 AM
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I didn't get a new humidistat, I soldered the resistor piece back on, otherwise it turns on, hopefully it will operate the solenoid.

I now have been informed that the HUM on the furnace board is fried and they said the whole board needs replacing, so I might be out of luck there.
 
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Old 02-16-10, 06:16 PM
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I tried a new transformer and wired the correct way, but the humidifier still doesn't work and the transformer gets really hot. Do you know what's going on?
 
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Old 02-16-10, 06:20 PM
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Bypass the humidistat, wire the two wires direct from humidifier to transformer.

FYI, the humidifier is going to run nonstop. We are jsut going to test this to see if the transformer gets hot or not.
 
 

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