I installed an Aprilaire 400A on my American Std (Trane) 2 stage variable speed furnace over the weekend. The furnace is model number S9V2D120U5PSAAA and it is tied into both propane and a heat pump. The board in the furnace has both W1 and W2 terminals. I noticed when the propane burner is active terminal W2 to B/C shows voltage so I hooked the white wire going to the humidistat to W2 and the humidifier works. However, when the heat pump is running in heat mode, W2 is not showing any voltage - I also checked W1 when in heat pump mode and it is not reading any voltage either. Any ideas? I apologize in advance if this has already been answered, I found many solutions for various issues but not one for this situation. thanks scott
You have a dual fuel application. W1 and W2 are furnace only connections.
I looked back at some of the other threads and didn't see that I provided a positive solution.
My recommendation is to use two relays to control the humidifier.
One relay for the heat pump and the other for the furnace.
Your furnace may have a HUM connection that could be used.
Post the model or part number off the furnace control board.
Another method just occurred to me. Use the electronic air cleaner connection.
No relays would be required.
I'll know better when I see what board you have.
Pete, thank you for the quick reply. The board has both EAC and HUM connections which according to the manual are 110V. I only want the humidifier active during heat mode. Attached is a picture of the board.
The EAC terminals are live when using the heat pump. They are also live using the furnace.
You could put a small 24v transformer on the EAC and that would supply switching power to the humidistat.
If you used this method.... you wouldn't use the "FAN ON" mode on the thermostat in the winter.
You'd turn the humidifier off in the summer.
If you don't like that idea you'd need two 24v relays. One connects to C and W on the furnace.
The other connects to C and Y on the thermostat or at the furnace board.
Thanks again Pete. One more question on how to wire this - The EAC terminals power the transformer - does one wire from the transformer go to one of the H terminals on the humidistat and the W terminal is not used?
One more question - since I already have the supplied transformer wired to the solenoid valve, could I connect the W terminal from the humidistat to the G terminal on the furnace board?
The W wire can only go to one voltage source. G is a voltage source that becomes live when FAN ON is used or in A/C mode. It doesn't get power in heating mode. Your back to two relays then.
Look closely at the diagram. The transformer is not supplying the solenoid with power. If you have a transformer supplying power form the solenoid.... then to use my idea you would need a second transformer.
As far as I know, I have a rebranded Aprilaire 56 controller, and a rebranded Aprilaire 5?? Humidifier (the top water connection is one I've never seen in photos, so it throws me on which model).
As Trane does not allow anyone to purchase parts, or do any work themselves, and that is the total opposite of my philosophy, I figured this forum would be super helpful.
A while back, I noticed the Humidifier was non-functional. I started out by replacing the saddle valve with a higher quality ball valve, and flushed the inlet line to the valve. It is attached to the cold water line, and I do not have a heat pump. Having very hard water, I noticed the solenoid valve was totally blocked. The strainer also appears to be missing. On a test bench, the valve did not function. I disassembled and cleaned it in an Ultrasonic cleaner, to the point of dissolving the yellow chromate finish. I then reassembled and tested with an adapter I fashioned to connect to the garden hose, and with 24 VAC applied, it now functioned correctly.
I then reinstalled, and turned the dial on the model 56 to the test position. It operated correctly for about 10 seconds, and never operated again.
24 VAC comes on as it should on R & C when the furnace calls for heat or the blower operates.
The temperature sensor reads the proper resistance compared to outdoor temperature.
Solenoid resistance is 29 ohms. The relay clicks audibly when the dial is advanced to higher humidity.....but no voltage is ever present on H & H to operate the solenoid. Connecting the solenoid to R & C to test, and it functions correctly.
It would appear the control board is now bad on the model 56.
The unit only seems to be sold complete, and model 56 seems to be discontinued. The price is well over $100.
Any tips on troubleshooting the PCB, or any other creative ideas? Failing that:
A possible cheaper solution appears to be this found on Amazon, using R & C to power a relay to switch 110 VAC to operate the replacement, and power the solenoid. An appropriate enclosure could be made, and the humidity sensor could be stuck on the inside of the duct above the hole for model 56.
[img]https://cimg9.ibsrv.net/gimg/www.doityourselft.com-vbulletin/2000x1504/20210222_142109_45d95926ccfb890054846717127d712bceeaed30.jpg[/img]
[i]Aprilaire model 56[/i]
[img]https://cimg1.ibsrv.net/gimg/www.doityourselft.com-vbulletin/2000x1504/20210222_142152_32c02c826d209423dfe5aab26557d559c1540434.jpg[/img]
[i]Aprilaire model 5??[/i]
[url]https://www.amazon.ca/KKmoon-Digital-Humidity-Controller-Measuring/dp/B07C4QT6XY/ref=pd_sbs_42?pd_rd_w=RZUFu&pf_rd_p=c2360efe-cd48-4541-ac20-e99c48f6c1e6&pf_rd_r=WQV5W98AFS8Z0NMPHDW2&pd_rd_r=6ec549ac-6ff4-4598-9352-a0213df29663&pd_rd_wg=yQ97d&pd_rd_i=B07C4QT6XY&psc=1[/url]
I installed an automatic humidistat 6 years ago as #7 on [url]http://www.skuttle.com/pdfs/compustat_install.pdf[/url] but it is failing and doesn't work very well now. Is there a reasonably priced alternative that installs with the same wiring?
[img]https://cimg9.ibsrv.net/gimg/www.doityourselft.com-vbulletin/556x506/fig7_81855f07ab708d0cab04cc1b939fcb2aec917edd.jpg[/img]
02-23-21, 04:41 PM
