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Dehumidifying Performance of 5 Dehumidifiers Lower than Claimed

  • 2016.02.15

During humid and wet spring, many families use dehumidifiers to keep their home dry and comfortable, and to dry clothes as well.  The Consumer Council tested 14 dehumidifier models, and found that for 5 models, the dehumidifying capacity was lower than what the manufacturer claimed in both the standard environment and in the manufacturers’ own test environment.  The situation is concerning.

Besides, half of the models, i.e. 7 of the 14 models tested in a standard environment, the daily dehumidifying capacity was lower than what was claimed (rated value) by about 5% or below.  In a non-standard environment, which is often used by manufacturers, 9 of the samples had a lower dehumidifying capacity than what the manufacturers claimed.  1 sample performed below its claim by as much as 16% substantially, the test results were sent to the Customs and Excise Department for follow-up.

Three Test Environments

The Council conducted the tests under 3 different environments with different temperature and relative humidity (RH):

  1. Standard environment: 26.7°C, 60% RH
  2. Manufacturers’ own test environment (non-standard): 30°C, 80% RH
  3. Low-temperature environment: 20°C, 60% RH

The tests included 12 compressor type models, 6 of which claimed to have higher daily dehumidifying capacity and dehumidifying speed (11.8L to 15.5L).  The other 6 models claimed a lower dehumidifying capacity and speed (7.72L to 10L).  Two desiccant-type models were also included.  All were priced between $2,080 and $5,880.

Test Results Do Not Match with Product Claims

Standard Environment

Referencing the Mandatory Energy Efficiency Labelling Scheme (MEELS) of the Electrical and Mechanical Services Department (EMSD) and based on the American national standard which better reflect the actual operating circumstances, the daily dehumidifying capacity of 7 samples was found to be lower than the claimed (rated value) by 1.8% to 5.1%.  These values are within the acceptable tolerance set for the MEELS (10%).

Manufacturers' Own Test Environment

Dehumidifying performance at non-standard environment is often used by manufacturers.  1 compressor-type model had a daily dehumidifying capacity about 16.8% lower than the claimed capacity.  There is a significant difference between the capacity claimed by the manufacturer and the test results.  The Council therefore passed the result to the Customs and Excise Department for follow-up.

Low-Temperature Environment

Some desiccant-type dehumidifiers are claimed to perform better than the compressor type in a low-temperature environment.  Test results revealed that 1 desiccant-type dehumidifier was measured about 10.5% lower than its claimed value in this environment.  The result was therefore also passed to the Customs and Excise Department for follow-up.

Urge to Stop Using Dehumidifying Capacity under Manufacturers' Own Test Environment

The Council concerns that most dehumidifiers still measure the daily dehumidifying capacity in the manufacturers’ own test environment, in which the temperature and RH are higher, instead of just measuring under the standard environment which can better reflect real life circumstances.  In reality, the dehumidifying speed slows down as the room humidity becomes progressively lower.  The dehumidifying capacity would therefore be higher in the manufacturers’ own test environment, which may confuse consumers into thinking the product is of higher efficiency.

In this test, for example, the dehumidifying speed of the compressor-type samples measured in the manufacturer’s own test environment was obviously higher than that measured under the standard environment by 54% to 90% (77% on average); on the contrary, the dehumidifying speed of desiccant-type samples was higher by 7% and 10% than that in the standard environment.  The Council has repeatedly urged manufacturers to stop using their own test environment because it does not reflect the actual circumstances of use, but no obvious improvement observed so far.

All compressor-type dehumidifiers being sold are required to carry an energy label issued by EMSD under the MEELS.  The dehumidifying capacity figure shown is measured in the standard environment following the MEELS specifications, a much more accurate reference to consumers.  The test results showed that the dehumidifying capacity of most compressor-type samples measured in the standard test environment matched the claimed value closely, while that measured in the non-standard test environment deviated more from the claimed value.

Grading Derived Different from Grade on Energy Label

From the test results, it was found that of the 12 compressor-type dehumidifiers tested, 7 qualified for the top Grade 1 rating and 5 qualified for the Grade 2 rating.

Comparing against the energy label, 4 models with Grade 1 rating on their energy labels had an energy-efficiency grading derived from the test results lower than that on their energy labels.  The difference in value was within the acceptable tolerance and did not violate the requirements of the MEELS.  Nevertheless, the Council informed EMSD the test results.

Furthermore, 12 models passed all 10 safety tests items conducted by the Council based on international safety standards.  The remaining 2 compressor-type models were found to have insufficient internal insulation distance or there was room for improvement in the resistance to heat or fire of some of the plastic materials.  EMSD stated that, according to the test results, all tested models are safe for use under normal operation.  For the 2 models with minor deficiencies, EMSD had approached the concerned suppliers for making necessary improvements to their products.

Annual power consumption of the dehumidifiers was calculated according to the MEELS.  Assuming that the dehumidifier is used for 450 hours per year in the standard environment and electricity costs $1.2 per unit, the 6 compressor-type models which have a higher dehumidifying speed cost $135 to $171 per year.  The 6 compressor-type models which have a lower dehumidifying speed cost $102 to $138.  The 2 desiccant-type models cost $177 and $200.

Consumers should be aware that these estimations do not take into account the dehumidifying speed.  Since the dehumidifying speed varies among different models, the number of hours they are used may vary accordingly and affect electricity bill.  Furthermore, some households may use the dehumidifier for over 450 hours every year, thus consumers need to take note of the usage for energy saving and expenditure.

Some tips for buying a dehumidifier:

Understand your actual need at home: if your home is large or you live close to the sea or in a humid district, or if you want quick dehumidifying, consider models with stronger capacity, and vice versa.

Check the energy label: all compressor-type dehumidifiers must have an energy label which shows not only the energy efficiency grade, but also the energy factor and dehumidifying capacity figure.  The higher the energy factor (litre/kWh), the more energy-saving.  The higher the dehumidifying capacity value, the higher the dehumidifying speed.

Check whether it has automatic humidity control: dehumidifiers available in the local market generally have this function, which automatically stops and restarts the machine according to the fall or rise in humidity.  This can save power while maintaining optimal moisture levels.

Look for model has wheels and handles: these make the device more mobile and are especially good for larger, heavier models.  Wheels that can move in all directions are more convenient than those which only move left and right.

Use throughout the year: compressor-type and hybrid-type dehumidifiers can easily be affected by the temperature and humidity.  Desiccant-type models are more stable and are probably more suitable for use in the winter and early spring when the temperature is lower.

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