Top critical review
18 people found this helpful
Quiet and works, but can be expensive to run.
on February 1, 2014
Update 2/3/2014: We actually bought two of these units. The first one, described below, works fine. The fan in the second one stopped running when set to medium speed. The heating element would run, but without any air movement to cool it. I shut it down very soon after discovering the problem. I would HOPE there is some sort of thermal breaker to shut down the unit in this scenario before it starts smoking/burning. I am returning the second unit for a replacement. Kudos to Amazon for its pain-free replacement policies. However, SPT lost a star in my rating. Again, the working unit is described below:
We bought this unit to dehumidify a 20' x 20', masonry workshop. Humidity is always a problem in the workshop. During the summer we run a compressor-type dehumidifier, but the workshop is only heated enough to keep pipes from freezing in the winter. At those temperatures, we can't run our compressor-type dehumidifier, and humidity runs in excess of 70%. We saw this device as being useful for putting just a tiny bit of heat in the building (for the water pipes), while staying on top of the humidity problem. And for this purpose it seems to be working very well. I pulled out a gallon of water and dropped the RH by about 10% after one day of running on medium speed (45 degF, 70% RH initially). I'm satisfied with that. We would have used the energy anyway with an electric space heater, but the dehumidifier gives us an additional return in the form of much-needed dehumidification. Win-win.
That said, it's not the most efficient device in the world. If you can run a dehumidifier in higher temperature air and don't mind the noise of a compressor-type humidifier, you can pull out MUCH more significant quantities of water in shorter time with the same electricity. How efficient is this dehumidifier? These are my test results:
Low speed, 55% RH, 50 degF: Pulled out 33 ml of water in 1 hr with 0.28 kWh of electricity, for a dehumidification cost of 8.48 kWh/L ($1.18 per liter of water where we live -- electricity priced at 14 cents per kWh).
Medium speed, 55% RH, 50 degF: Pulled out 85 ml of water in 1 hr with 0.34 kWh of electricity, for a dehumidification cost of 4.00 kWh/L ($0.48 per liter of water). This was the most efficient setting.
High speed, 55% RH, 49 degF: Pulled out 120 ml of water in 1 hr with 0.61 kWh of electricity, for a dehumidification cost of 5.13 kWh/L ($0.72 per liter of water).
And then in the overnight test in the workshop, medium speed, 45 degF, 70% RH, roughly a day (maybe more) of run-time, 10.65 kWh to extract 3.5 L of water, for a total efficiency of 3.04 kWh/L ($0.42 per liter of water). RH dropped by perhaps 10%, according to the humidity indicator card I keep hanging from the ceiling fan.
I can see how this dehumidifier would also be very useful inside a living space. At even the high speed setting, the unit is far, far quieter than a compressor dehumidifier. It is quieter than my computer fans on medium speed, the most efficient setting. I frankly wouldn't bother with low speed, but if you do, it's impressively whisper-quiet on that setting.
I can also see this dehumidifier used in a boat during the winter. It would throw off just enough heat to keep our 31' sailboat from icing up, and it would keep the cabin dry. The drain tube could be run to the bilge, where the condensate would be ejected by the bilge pumps. We might try that in the future.
For other uses (e.g. basement), you're better off with a compressor-type dehumidifier if the temperature is high enough to run one.
The humidistat seems rather inaccurate, as the unit would not run in the 50% RH mode when the humidity was around 70%. In the 40% RH mode, it would begin to run. I just switched to manual.
Our unit makes a short, tiny squeak whenever the desiccant wheel makes a complete revolution (once in approx. 2 min). It's not annoying, but I do notice it. You can also smell the heating element at times. It's not an obnoxious smell, but it's there.
The unit is attractive and well made. I love the innovative design, and part of the reason I purchased it was to reverse engineer it. It is a very affordable example of an adsorption dehumidifier, and it is unique in this market. I hope to design a whole-house adsorption dehumidifier from silica gel (cheapest = silica gel cat litter), using convective airflow from a solar chimney to dehumidify the media. By far the largest power draw from the SPT dehumidifier is the heating element, and a solar chimney design would eliminate that energy cost. But for now, for what we're doing, this SPT dehumidifier is a very clever little unit that fills a niche in our humidity control strategy. Oh, and for all it's worth, I didn't give it 5 stars only because of the inefficiency of the technology. If energy were free, and if there were no such thing as global warming, heck, I'd give it 5 stars.