Heck of a big humidifier, may require some big muscles to fill

My house is small, about 1000 square feet. This humidifier is big enough for a house at least twice that size. The quality is good enough that buying two of them, making two humidifying zones for your 3000 sq. ft. house, would work out fine.

How do you know if you need a humidifier? First, you’ll need a hygrometer (humidity meter) to measure the humidity in your house. If the humidity is too low, it’s hard on the nose, and you’re prone to nosebleeds and respiratory infections. Also, low humidity dries out and shrinks the wood in the house, which is most harmful to pianos, other musical instruments, and african violets. If the humidity gets too high (above 50%), the mold-spore count will take off, contributing to sick-house syndrome like any other indoor pollutant.

The combination of humidifier and hygrometer will help you control the humidity within its proper limits (40% to 50%). The Holmes HM-3500 humidifier has a couple of settings to control how much water it will add to the air - and how quickly, but they make no attempt to suggest that any particular setting will equate to a particular room-humidity. It’s up to you to find a way to determine what the humidity is actually being raised to.

To measure humidity, I use an Acu۰Rite digital thermometer/hygrometer from WalMart. I must expound on my hygrometer, since using a humidifier without one can do more harm than good. Compared to a similar item from Radio Shack, the Acu۰Rite hygrometer-display updates 10 times more quickly, which means you can watch the humidity rise on the meter. It can step through a 10% change in humidity before the Radio Shack display has even budged. When the Radio Shack finally catches up, they display about the same humidity, so at least they confirm each other’s readings. Sorry I can’t find the Acu۰Rite listed in ePinions (yet), and the meter has no model number (!), not even inside the battery compartment. Still, I recommend my Acu۰Rite. For $25, it’s about 2 1/2” wide, 4” high, and 1/2” deep, props up on a tabletop with its plastic kickstand, has three lines of display inside a round display area; inside temp, outside temp (with a wire sensor), and inside humidity. Includes hi-lo memories, clock, etc.

This year, the temperature outside stayed below 20°, frequently dropping to 0°, for at least a month. Leaving a vaporizer on continuously was not enough to get the humidity over 30%, even after adding a pinch of salt to the water to speed up the vapor output. Since I’m aiming for 40 to 45%, I broke out the Holmes HM-3500.

I put my HM-3500 next to the air-intake vent of my forced-air system. The cloud of humidity around the humidifier gets sucked up into the intake vent, and the humidity is delivered throughout the house. I believe no room vaporizer or cool-mist device is able to deliver as much humidity as the HM-3500. In fact, the HM-3500 is too big for a single room, and only seems worthwhile if there is some kind of whole-house air-circulation to spread out the humidity.

The HM-3500 has a thick 8” high wick (sponge) shaped into a 6” ring, which looks rather like a giant automobile air filter. The wick sits in the humidifier base, in a pool of water. Hovering over the wick is a powerful fan the sucks air through the wick, humidifying the air and blowing it into the room. Like the HM-3500, replacement wicks are available at WalMart. Since that time, I’ve learned to do much less shopping at WalMart, but that’s getting off topic. It’s a popular humidifier, and I’ve also seen it in neighborhood hardware stores.

The fan has three speeds. Low is very quiet, Medium isn’t bad. High is very dramatic, sounding like a small hurricane, but aside from the big “whoosh,” there is no extraneous rattling. I’ve used High to quickly deliver massive amounts of humidity into the air. Low is sufficient for regulating the humidity inside the small house if outside temperatures drop to 15°; medium was good almost to 0°. If your house is larger, you will need to run the fan at higher settings than I did.

When the outside temperature drops to 15°, the ice forming on the inside of my cheap windows gets pretty thick, so I allow the inside humidity to drop to 35% when the outside temperature drops below 15°. With better quality building materials, you might prefer to keep the humidity low enough so that almost no condensation forms on your windows, or else risk rotting your wooden windowsills. Vinyl windows should have more resistance to condensation compared to wood.

Aside from the fan speed, the HM-3500 also has a variable humidistat, which turns the fan On and Off to regulate the room humidity.

Unfortunately, the humidistat in the HM-3500 frequently does a poor job at regulating the humidity. The best situation is when the temperature outside is steady, and the heat in the house cycles on and off with a constant frequency. In that case, the humidistat will regulate the humidity just fine. Such will often be the case during 12 hours of daytime or nighttime.

But if the temperature drops outside and the house heat comes on more frequently, which dries out the air in the house more quickly - such as when nighttime arrives, the humidity will drop unless the humidistat control is nudged upwards. And when the sun comes back out and the heat comes on less often, the indoor humidity will tend to rise 5 or 10 percent unless the humidistat is turned back down.

Also, the humidistat does a poor job of regulating if the indoor temperature varies. For instance, if the temperature starts at 72° and the humidity is 40%, and you turn the temperature down to 65° before going to sleep, the humidity will rise to almost 50% unless you also notch down the humidistat before going to sleep. And if you leave the house over the weekend, you might want to turn down the heat to 55°. Without also adjusting the humidistat, you’ll find the humidity soars to 60%, but you won’t realize it until you get home Sunday night. The first sign will be the paint peeling off the walls (just kidding). The only calibrations on the humidistat are dots painted on the cabinet, but it’s easy enough to learn how many dots the setting should be reduced so the humidity regulates at 40% at the lower temperatures. (I find the humidity changes about 10% per dot.)

Putting the fan on Low can be expected to be sufficient when the outside temperature drops to a certain point. Below that temperature, you will notice the inside humidity starts to drop even though the fan is staying on continuously. Turning up the humidistat won’t help, since the fan is already on constantly. That’s your cue that the fan needs to be turned up to the next higher setting. With the changing weather conditions, the humidistat will certainly also need to be adjusted.

You see how a hygrometer is necessary to monitor the humidity with some accuracy. The inside humidity will change as the outside temperature changes from day to night or from day to day, or as you change your thermostat setting. Unfortunately, the Holmes humidistat is not a set-it-and-forget-it control. If you’re compulsive, you’ll appreciate having one more thing to adjust periodically.

The biggest design-problem is that the humidistat is integrated into the humidifier, and has trouble sensing the humidity elsewhere in the house. A more Cadillac-type approach would have the humidistat-sensor remotely placed in another room of the house.

A big-output humidifier deserves a big water tank reservoir, and the HM-3500 has two of them, each holding up to 2.2 gallons of water. That’s heavy. Also, the base holds another 2 gallons of water, for a total of 6.4 gallons, max. That should only require refilling every two or three days. A yellow light comes on when the level is very low.

The tanks are feats of engineering prowess. Handles are integrated into the tops of the tanks, and have been sturdy enough to hold 2.2 gallons of water without breaking. The top of each tank has a graceful, curved form, but that’s a real pain when it becomes necessary to rest the tank on its top while filling water into its bottom opening, especially if you’re low on hand strength. The bottom opening has a 3 1/2 inch diameter screw-in plug with a heavy rubber gasket. It takes some hand-strength to get your hands around this plug to tighten and loosen it against the rubber gasket. My gaskets are still in good condition after 3 winters’ use.

In the center of each tank’s plug is a valve, with it’s own little rubber gasket. When the tank is positioned right-side up in the humidifier, water comes out of the small valve. (Don't worry, no water comes out of the valve until the tank is placed into the humidfier's base.)

To fill the tank, turn it upside down and remove the plug. Not too much of a problem when empty and lightweight. I recommend doing this at the bathtub. Place the plug within arm’s length of the bathtub spout, so you won’t have far to reach for the plug after the tank is filled. The tank fits conveniently underneath my bathtub spout, but since the “top” of the tank is curved, it’s a trick to keep the tank sitting steady under the spout when the water start getting heavy. When the weight starts getting unmanageable, that would be a good time to stop filling the tank any further - it’s not really necessary to fill the tanks all the way.

Then you have to take the tank out from under the spout and replace the plug, or perhaps replace the plug and then pick up the tank. Either way, it would be a lot easier to screw the plug back in if the tank had a flat top, so it wouldn’t require such a balancing act. There is no reason that the tank couldn't have been designed with a flat top. Since the top is slanted, it’s going to require some muscles to hold the tank securely while the plug is being screwed on.

Plastic threads on the plugs seem like a cross-threading disaster in the making. Be careful not to cross-thread! First, screw the plug counter-clockwise to make sure the delicate plastic threads are not cross-threaded. When the plug seems to click into place, then gently screw it in clockwise. When you’re extra sure the plug isn’t cross-threaded, then you can tighten it against the rubber gasket securely.

Gorillas should be warned that it is not necessary to over-tighten the plugs. In my experience, if it is securely water-tight, the plug will not self-loosen, and further tightening would only stress the rubber gasket unnecessarily.

After tightening the plug, the unruly tank is turned upright. This maneuver can also be awkward, although the slanted handle in the top now becomes useful. I fill my tanks all the way, and am amazed every time that water doesn’t come gushing out the bottom when I turn a tank over. Assuming you’re equally lucky, the tank is then placed into the base of the humidifier, where a wide plastic “pin” pokes into the valve, and lets water run out into the base. The tank drops into place without resistance, no muss no fuss. The pin is cone-shaped, which helps the tank to position itself correctly as you set it down.

Then, you can fill the other tank, too.

The base holds 2 gallons of water. Even though 4.4 gallons of water are delivered, the system does not allow the base to overfill. 2 gallons of water in the base keep the big wick very wet. It is simple and ingenious.

The whole thing is 20” wide, 12” deep, and 20” high. About 10” of the width is from the two water tanks sitting on one side of the base, and the other 10” is the wick / fan assembly on the other side. The fan assembly can be also be lifted off and placed back into the base easily, although this shouldn’t often be necessary. The fan is not heavy or delicate, but lacks a handle, so don’t squeeze its plastic cage too hard when you remove it.

The base is on castors, which may come in handy, some day.

The side of the fan assembly has a color graphic, which shows how the wick is expected to discolor as it ages, and it is easy to compare the wick to the graphic. In my case, after 3 seasons, the wick has only just begun to discolor, so maybe it will be usable for another few seasons.

The instructions are pretty good, and were obviously written by someone who knows English. Some strange instructions include that you immediately re-fill the tanks after they partially empty into the base, which is more compulsiveness. Feel free to wait a day or two, then refill the tanks. They also mention adding Holmes Water Treatment to help prolong the life of the wick and “soften mineral deposits.” Well, no one has harder water than I do, but my base is not accumulating any sediment. Although my wick is only lightly colored, its form is showing some deterioration, which might be due to mineral damage. More likely, the deformation is due to sitting in water for months at a time. But I’ll be happy to replace the wick in a few more years instead of having to worry about locating and purchasing some strange solution and adding it to my water vapor.

Looks like the retailers are calling the wick a "filter."