If you've been dealing with dry air, scratchy throats, or that annoying static electricity every time you touch a doorknob, digging out your aprilaire 720 manual is probably the best move you can make today. This specific model is a bit of a workhorse, and while these units are built to last, they definitely aren't "set it and forget it" machines. Like anything else in your home that deals with water and electricity, they need a little love and attention to keep doing their job effectively.
I know how it goes. Most of the time, these manuals end up in a kitchen junk drawer or tucked behind the furnace in a dusty plastic bag. But once you actually sit down and look through it, you realize it's more than just a list of parts; it's basically a roadmap for keeping your home's air from feeling like a desert in the middle of January.
Why You Actually Need This Document
It's easy to think you can figure out a humidifier just by looking at it, but the Aprilaire 720 is a fan-powered unit, which makes it a little more complex than the basic bypass models. The manual is your best friend when it comes to understanding how the water flow is controlled and how the internal fan should behave. If you've ever noticed the unit making a weird clicking sound or if the air just doesn't feel any more humid after running it for three days, the manual is where the answers live.
One of the most important things you'll find inside is the wiring diagram. Now, I wouldn't suggest poking around in the wiring unless you know what you're doing, but having that diagram handy if you're calling a technician can save you a lot of time and money. It tells the pro exactly how the solenoid valve is supposed to communicate with the humidistat. Without it, they're just guessing based on general knowledge, which can lead to longer service calls.
Breaking Down the Installation Section
If you're just now installing a unit—maybe you found a new-old-stock model or you're moving one from a different house—the installation portion of the aprilaire 720 manual is non-negotiable. Because this is a fan-powered unit, it doesn't rely on the pressure difference between the supply and return air ducts. Instead, it pulls air through the water panel using its own internal motor.
This means you have more flexibility on where you mount it, but you still have to be careful about where you tap into the water line. The manual usually suggests using the hot water line if possible. Why? Because the heat helps the water evaporate more quickly, which increases the efficiency of the unit. It's those little "insider" tips in the manual that make the difference between a humidifier that kind of works and one that actually makes your house feel comfortable.
The All-Important Water Panel
If you flip through the pages, you'll see a section dedicated to the "Water Panel." In the industry, we often call this the filter, but it's actually the heart of the machine. For the Aprilaire 720, you're usually looking at a #35 Water Panel.
The manual will tell you to change this at least once a year, usually at the start of the heating season. If you ignore this, you're asking for trouble. Over time, minerals from your water—things like calcium and lime—build up on the mesh. Eventually, it gets so crusty that air can't pass through it anymore. Not only does this stop the humidification process, but it can also cause water to backup and leak onto your furnace. Nobody wants a rusted-out furnace over a $15 filter.
I've seen people try to "wash" these panels. Don't do it. They have a special clay coating designed to hold water and encourage evaporation. Once you scrub that off or soak it in vinegar, it's basically just a piece of metal mesh that won't hold water. Just follow the manual's advice: toss the old one and slide in a new one.
Troubleshooting the Common Stuff
One of the most common questions people ask when they look for their aprilaire 720 manual is: "Why isn't my humidifier filling with water?"
The manual usually walks you through a few quick checks. First, is the humidistat actually calling for humidity? If your house is already at 45% humidity and your dial is set to 35%, the unit won't turn on. It's doing its job by staying off.
Second, the solenoid valve might be stuck. This is a little electric valve that opens up to let water into the distribution tray. If you have hard water, these valves are prone to getting clogged with sediment. The manual explains how to check if the valve is getting power. If it's humming but no water is coming out, it's likely clogged or dead.
Then there's the drainage. These units are "flow-through," meaning they use more water than they actually evaporate. The excess water carries away the mineral deposits and goes down a drain tube. If that tube gets kinked or clogged with gunk, you're going to have a puddle on your basement floor. The manual shows you the proper way to route that tubing so gravity can do its thing.
Understanding the Humidistat
The manual also goes into detail about the humidistat—the little dial usually mounted on your return duct or near your thermostat. This is the brain of the operation. Modern versions of these can be automatic, meaning they have an outdoor sensor that adjusts the indoor humidity based on how cold it is outside.
This is actually pretty crucial. If it's -10°F outside and you have your indoor humidity set to 50%, you're going to wake up with ice and condensation on your windows. That moisture can rot your window sills and lead to mold. The aprilaire 720 manual provides a handy chart that tells you where to set the dial based on the outdoor temperature. It's a bit of a balancing act, and that chart is the cheat sheet you need to get it right.
End of Season Maintenance
When the birds start chirping and you turn off the heat for the year, you shouldn't just walk away from your humidifier. The manual recommends a "shut down" procedure. This usually involves turning the humidistat to the "off" position and closing the water saddle valve.
Closing the water valve is a big one. If you leave it pressurized all summer, and that solenoid valve happens to fail, you could end up with a slow leak that goes unnoticed for months. A quick turn of the valve saves you a lot of potential headaches. I also like to take the water panel out at the end of the season so the unit can stay dry and clean during the humid summer months.
Keeping Your Air Healthy
At the end of the day, the reason we care so much about the aprilaire 720 manual is because we care about the air we breathe. Properly humidified air is better for your skin, your wood floors, and even your immune system. Dry air dries out your mucous membranes, making it easier for cold and flu viruses to take hold.
By following the instructions in that little booklet, you're ensuring that your home remains a comfortable sanctuary. It's not just about the machine; it's about the environment it creates. So, if you haven't looked at your manual in a while, maybe go find it. Give the unit a quick inspection, swap out that crusty water panel, and make sure the drain line is clear. Your house (and your itchy skin) will thank you for it.
It's funny how a simple piece of paper can be the difference between a frustrated homeowner and a comfortable one. Even if you consider yourself "handy," there's always some little detail in the specs that's easy to forget. Keeping that manual nearby—maybe even taping a copy to the side of the furnace—is just one of those smart homeowner moves that pays off every single winter.