Archive for October 30th, 2010

Dehumidifier Performance

Having ever so many books & papers in the Basement Shop & Office, I must run a dehumidifier to fight the mildew to a standstill. It’s actually under 55% most of the time, but humid summer days are killers.

Being the sort of bear who owns a Kill-A-Watt meter, I jotted down dates, runtime hours, and kWh when I filled each 5-gallon bucket. Eventually, we acquired a cheap scale that found its way under the buckets to weigh the outgoing water.

My data collection foundered on errors of omission, power failures, and general forgetfulness, but, nonetheless, a few interesting numbers emerged.

Outside weather:

  • Dry weather = 0.14 kWh/elapsed hour
  • Wet weather = 0.37 kWh/elapsed hour

It draws about 485 W, so the duty cycle works out to

  • 0.14 kWh/hour -> 140 W -> 29%
  • 0.37 kWh/elapsed hour -> 370 W -> 76%

If I were more industrious, I’d grab a plot of daily humidity from the NWS and rub those numbers against it, but … maybe next year.

The thing requires somewhere between 2.0 and 3.5 kWh to extract each pound of water. It’s rated at 1.6 liter / kWh = 3.5 lb / kWh, undoubtedly under standard conditions, so the actual efficiency is in the right ballpark.