Aprilaire 56 Humidistat Controller - Digital Humidity Control for Home HVAC Systems | Perfect for Basements, Bedrooms & Dry Climates

I had to return this item in mid-shipment (it turns out my HVAC guy got a faulty reading and my controller was not faulty after all). And excellent service on that return. Thanks for having this product available and fairly reasonable price comparatively, shipping so promptly, and being so agreeable with the return. Will definitely return in future if/when I need that control panel.Purchasing the Aprilaire 56 Humidisat Controller on Amazon indirectly repaired my humidifier problems without the need for a service call from my HVAC repairman. I recently had a new furnace and central A/C system installed in April 2018 after which my humidifier no longer worked. Considering it was the end of spring, I ignored the issue knowing I would address it with my HVAC installer when the winter heating season arrived. After a brief in home test of my humidifier system, my HVAC repairman informed my that my Aprilaire 56 humidistat controller was most likely the problem considering a direct wire test of the water control valve worked fine. Myy HVAC service location did not get back with me on replacing the controller so I therefore decided to order one on Amazon. After replacing the controller, the humidifier still did not work (water valve would not click open). Fortunately....the new controller came with instructions and a wiring diagram along with a manual component which is simply a resistor. Long story short, I discovered that the HVAC people apparently broke off my outdoor temperature sensor. I discovered this after reading the trouble shooting guide that came with the new controller as my RED LED light on the controller board still came on. Rather than go through the trouble of replacing the outdoor temperature sensor (which does come with the controller), I simply installed the MANUAL electrical component/resistor across the two contacts where the outdoor temperature sensor is normally connected. ALL works well now .....with NO THANKS to my professional HVAC installers. In my case.....my controller was not actually broken however the outdoor temperature sensor was damaged when they installed my new central AC. I now have a backup controller and know a lot more about how my humidifier actually works rather than depending on an HVAC repairman who really did not seem to know much about the Aprilaire 56 settings, etc.. Again...without reading the instructions and understanding the various settings on the controller, you really are depending on someone who may know nothing about humidifier system. Instructions are very clear and helpful. I really liked that it came with all the extra components including the outdoor temperature sensor even though I actually like the manual operation better. There is only six wires that connect to this controller so replacement is quick and easy. Just make sure you have a mini straight blade screwdriver handy.My old humidistat wasn't operating properly and frankly looked like it was getting moldy as spots were popping up on it. I ordered this as a replacement for the one I had. This was a perfect replacement for my old one, as the wiring locations were exact. It only took a few minutes to remove the old one and insert the new one in place. I followed the setup instructions and he was working as normal. It is a bit pricey but who wants to but a complete new humidifier if they don't have to? This works great and is cheaper than other places sell forA little research and I find out that my 600 series Aprilaire humidifier has the ability to use a wired remote outdoor temperature sensor that will allow for automatic humidity adjustments. That sensor is used with this humidistat and as a added bonus it does come packed in the box with the humidistat. As it may also be set to Manual as well, it comes with a bypass resister that pops perfectly into place. The sensor itself is about 3 inches in length, and connected to a cable about 2ft in length. the instructions state where the sensor can be mounted. Many reviewers have used a multitude of cabling to cover the distance gap: telephone wires, speaker wires, old unused AC cables that run outside, etc.I needed to replace our 10 year old Humidistat Controller as the old one lost sensitivity and only started the water flow to the humidifier when the humidity in the house was very low. This was the exact replacement for the Aprilaire Model 56 Automatic Humidistat Controller which made it easy to get the wiring correct. I will note that the controller looks a bit different than the one pictured on the amazon site when I order the product on 10/2013 since the controller pictured appears to be a Model 4655 Analog Humidistat. The new controller works well. I am running it in automatic mode, and I installed the thermocouple in the air supply duct to the furnace about 15 feet from the controller, as required to get it close to the outside wall of the house as directed by the install instructions. To get to 15 feet, I used wire extension wire and soldered the wire connections to the thermocouple lead wires. It would have been nice if the thermocouple came with long lead wires that could be cut to length. The old controller was run in manual mode without the outdoor temperature sensor.Replacement for 10 yr old Aprilaire 600 humidistat is now working well after solving one install puzzle: With wiring correctly connected and having checked circuits on both the outdoor temp probe and the water solenoid control, the humidistat would not activate the solenoid. I could hear the humidistat switch close when rotating the control knob and when switched to RESET, but the solenoid would not open and there was no voltage at the solenoid wiring terminals. Finally, with trial and error approach, I toggled the black bypass/non-bypass switch on the circuit board (visible just above the top of the snap-out wiring panel opening)--to the right and then back to the left. Either that switch wasn't making good contact when the humidistat was shipped to me, or it resets a circuit when toggled, but the solenoid immediately clicked open and water started flowing to the water panel. Problem solved. I find nothing in the humidistat print or online documentation that describes this problem and solution.very easy to install.IDENTICAL REPLACEMENT BRAND NEW IN A BOX. INSTALLED IN MINUTES AND WORKS LIKE A CHARM. GREAT DEALING WITH AMAZON. GOOD PRICES EFFICIENT DELIVERY SERVICE