Why: I bought the Bemis 4D7-800 humidifier because I live in Arizona where the air is very dry most of the time. I also bought a piano recently and would like to keep the house humidity level around the recommended 40-45% humidity level.
When: I ordered this unit from an Internet shopping store about 3 months ago. It came in a box of parts that required some simple assembly.
What's in the box: The unit consists of a fan housing with the build in digital humidistat controller, the main tub, two water tanks (2.7 gallons capacity, each), a filling hose, tank covers, evaporative wick, simple air filter, and 4 wheel casters. The main tub is a little flimsy but is firm enough after all the pieces are put together.
Main settings: The main control is simple, with only 2 buttons to control all operations. This simplicity is also an annoyance. One button controls the fan speed. The other button is used to set the desired humidity level in 5% increment. Fan speed increases on each press of the fan button (total of 14 steps) or stop if you hold the button down for a few seconds. The Humidity level button increases desired setting by 5% on each press or jump up rapidly if press and hold. In each case, the level rolls around after it reached maximum. As you can see, it is not easy to decrease fan speed or humidity level.
Using it: The entire unit rolls on wheel so it is easy to move around. Filling the two water tanks is a little awkward at first but you get the hang of it after a few tries. It is simple to use: fill water tanks, drop them in the tub, plug in power and set fan speed and humidity level. The unit turns its fan on when it senses that humidity level is below your setting.The fan draws air in from the back through a filter wick soak in water and blows moistened air out the top. The fan is turned off when the humidity level is more than 5% above setting.
Fan noise level: Fan noise is generally acceptable to me. At low speed, it is barely noticeable in daytime with TV or music on. It is definitely more noticeable at night when ambient noise is low.
Performance: At the 2nd lowest speed setting, it took about a week to increase and maintain the humidity level of a 2300 sqf house, in mid Arizona 110F summer, from the low 30% to mid 40%. I had to refill 1.5 tanks a day. In the current late summer time and after some rain, the house humidity is being maintained at about 46% with one tank refill every two days. One thing I've been noticing is that the humidity meter on the control unit can fluctuate up and down by 5-7% (even with the fan off). This means that the fan sometime turns on for short period of time.
Special requirements: Arizona water is hard so after one tank full of use, I can definitely see the mineral deposit build up. I do have reversed-osmosis water system so I use this exclusively to fill the tank now. I add a small cup of anti-bacterial treatment solution to every tank of water filled. Even with this treatment, I still have to break the unit apart about once a month to clean off the slimy brown stuff around the bottom of the tub. It is easy to disassemble and reassemble everything. The anti-bacteria treatment solution (about $5) is hard to find locally but it is available on the Internet & Ebay. The evaporative wick also needs to be replaced once a season (at about $15) and is also hard to find locally.
Overall, it is a little troublesome to maintain but it's worth it to me to get more moisture into the air at home. So far, this humidifier is working great. I'll give an update after using it another season.
Update June 08 2007: The unit is still working good. I've replaced the wick 3 times. I've switched from filtered water to tap water and it created heavy mineral deposit on the wick but this does not seem to affect the moisture output. The unit works better in the summer than winter. It does keep the house humidity level above 35%. I used to have dried nose problem but not anymore. The noise level is high on any speed setting above 3 bars. I found the antibacterial solution at the local Sear store but I still have to buy the wick on EBay.
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