Some manufacturers of dehumidifiers have been found to consistently use double sets of testing conditions in an apparent tactic to boost their dehumidifying capacity claims.
One set of condition is the manufacturers' own set of condition in their favour.
The claims of dehumidifying capacity between the two sets of conditions effectively differed by over 60% and in some cases, even by 100% or more (for example, difference between 12.5 litres and 28 litres per day).
This was revealed in a Consumer Council test on 12 models of dehumidifiers - 10 compressor types and two others, a desiccant and a hybrid type.
This practice of double claims is as baffling as it is confusing to the unwary consumers in comparing dehumidifying capacity of the product.
To verify the true values of the claims, the samples were put to test, first, in the standard environment as stipulated in the ANSI/AHAM (American National Standards Institute/Association of Home Appliance Manufacturers) standard i.e. at a constant temperature of 26.7℃ and relative humidity (RH) of 60%.
Under this standard test environment, only 4 samples were found to slightly over-claim their dehumidifying capacity, i.e. slightly below their claimed values, with discrepancy of between some 1% and 4%.
Second, the samples were subjected to the manufacturers' own test environment at 30℃ and 80% RH. Ironically, the results showed the problem of over-claims of dehumidifying capacity to be even more widespread.
Under the manufacturers' own test environment, a total of 8 samples were measured to be lower than their claimed values (by 2% to 24.2%), with 4 of them significantly less by around 24.2%, 21.6%, 14.9% and 14.4% respectively.
Consumers are advised to refer to the dehumidifying capacity rating on the energy label, under the Mandatory Energy Efficiency Labelling Scheme (MEELS), when choosing dehumidifiers of the compressor type.
Under the MEELS, the dehumidifying capacity is measured on the basis of the standard test environment of the ANSI/AHAM. The manufacturers' own favourable test condition is not a standard test condition prescribed for MEELS nor adopted in standards of any major countries.
In the view of the Council, the ANSI/AHAM standard environment of 26.7℃ and RH 60% is a more realistic measurement of dehumidifying capacity.
In actual usage, the relative humidity will become progressively lower after the appliance has been in operation for a while. Therefore the humidity does not stay consistently at a high level of 80% as suggested by the manufacturers.
When choosing the desiccant and hybrid type dehumidifiers which are not within the scope of MEELS, consumers should be aware of the test condition adopted by the manufacturers for dehumidifying capacity rating.
The compressor type and the hybrid type samples were found to be generally higher in energy efficiency than the desiccant type sample. All 10 compressor type samples were able to meet the respective requirements of MEELS: 6 samples were qualified for the top Grade 1 rating and 4 samples for Grade 2 rating, according to the test.
Some useful tips for consumers in purchase of dehumidifiers:
- Choose a dehumidifier according to the size of the living space and the surrounding environment, for example, a higher dehumidifying capacity per day is needed if close to waterfront or in a high humidity area.
- Pay attention to the Energy Label on the dehumidifier: the higher the energy factor, the more energy it saves. As for dehumidifying capacity per day, a higher value means a faster dehumidifying speed.
- A dehumidifier equipped with a bigger water tank will reduce the frequency of emptying the tank; one with a castor or a handle will make it easier to move around.
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- 2014.02.17