Danby DDR3010E Dehumidifier Fan Runs Continuously
Lasted 11 months and then quit working. Took it back for warranty and Danby replaced unit. I guess they don't bother repairing them as the freon had leaked out. Replacement unit is DDR30E and it says the fan never shuts off. Not sure if I like the fact that the fan never shuts off. I think I might return the DDR30E.
This review raises a common concern among dehumidifier users - dehumidifier fans that run continuously. I am asked about this all the time and thought that a few words on the subject might be helpful.
As you know a dehumidifier has a fan which sucks in air from your room and passes it through the dehumidifier to be dried. It then pushes the cooled air over the condenser coils and returns it to the room drier, and a little warmer than before.
The dehumidifier also includes a humidistat. The humidistat tests the air and figures out its moisture content. The humidistat is programmed, by you, to cycle the dehumidifier on and off to maintain a given level of relative humidity, usually around 45-50%.
If the humidistat finds that air is wetter than you want it to be it switches on the compressor and the unit will remove water until it is back at your chosen level. In order to check the air it needs to take a fresh sample from the room and this is the other purpose of the fan; it sucks in air for the humidistat to check.
There are two ways in which this can be done.
- The fan runs continuously so that the air can be checked in "real time", or
- The fan is switched on at intervals, usually every hour, and run for a few minutes to see if the air has gotten any wetter since the last time it checked.
Many folks dislike dehumidifiers in which the fan runs all the time. There are two main objections; noise and energy use.
If noise is your main objection you will probably choose a dehumidifier which samples the air for a few minutes every hour, despite the disadvantage which I will talk about in just a moment.
In a properly functioning, well made dehumidifier the fan is the main source of noise. The compressor, although audible, should not be too intrusive when it is relatively new. As the dehumidifier ages and the compressor wears it can become noisier, in just the same way as your elderly refrigerator buzzes more loudly than a new appliance. Well made dehumidifiers don't suffer from severe secondary vibration, which is a major cause of intrusive noise levels on some of the dehumidifiers we do not recommend here.
As far as energy use goes the "energy hog" is the compressor; the fan uses no more than a typical light bulb when it is running. This may be an additional energy cost in some circumstances but, on the whole, continuously running fans can actually save
Most dehumidifiers are used in basements so let's think about a typical basement of, say 1200 square feet. Basement ceiling heights vary but we'll assume a height of 7'6". This gives us a basement with a volume of 9000 cubic feet. If you are using a portable home dehumidifier you may well have chosen the biggest available, around 70 pints per day.
A typical 70 pint dehumidifier, the Frigidaire FAD704DUD for example, has an air flow of 330 cubic feet per minute on the higher of its two fan speeds. It takes about 27 minutes for 9000 cubic feet of air to pass through the dehumidifier at that flow rate.
The air in the basement does not have a uniform relative humidity. RH varies with temperature so the air near the floor has a higher RH than the air nearer the ceiling. The temperature of the earth is always less than the air temperature so near the walls of the basement, which are relatively cool, the air is cooler also.
If your dehumidifier is sampling the air once an hour, for about five minutes, how accurate will be the measurement taken by the humidistat? The dehumidifier has only sampled about 20% of the air in the room in that time. In addition, while the fan has been idle the movement of air in the basement has stopped. Had the fan been operating for the entire hour the total air volume of the basement would have passed through the dehumidifier twice, with moist air being mixed with drier air and air movement being maintained throughout, giving a more accurate reading.
It is for this reason that many manufacturers choose to design dehumidifiers with continuously operating fans. Accurate humidity readings save energy by ensuring that a dehumidifier only operates for the minimum time necessary to control RH to your programmed setting. With intermittent sampling the dehumidifier may
underestimate humidity and then have to play "catch up" while dehumidifying, when the continuous air flow provides a more reliable (larger) air sample.
For this reason the "light bulb" cost of running the dehumidifier fan continuously will be more than offset by the reduced time that the "energy hog", the compressor, is running.
It is an entirely reasonable thing to prefer less noise to greater energy efficiency, or vice versa, but it's impossible to have both. Decide which is your
priority and, please, be aware of the down side of your choice.
To help you, once you have decided, may I recommend two dehumidifiers in which the fan does not run continuously. The Alen MDF3-74 and the Winix WDH871. The distinctive feature of the Winix is that it is one of the few portable home dehumidifiers to have an internal pump. The pump will force the water upwards, if necessary, to a height of up to 15 feet.