During humid seasons, dehumidifiers can help remove moisture in the air. There are various types of dehumidifiers on the market, and they vary in dehumidifying capacity (i.e. rate of dehumidification) and energy efficiency. Consumers should be careful when choosing the appliances.
Consumer Council conducted a number of tests on 12 dehumidifiers: 9 compressor types, 2 desiccant types and 1 hybrid type. Test items included dehumidifying capacity, energy efficiency, operation under extreme conditions and low temperature, as well as safety performance.
Test results showed that in a standard environment (ANSI/AHAM standard, or American National Standards Institute/Association of Home Appliance Manufacturers standard, which is set at constant temperature of 26.7℃ and relative humidity (RH) 60%), the daily dehumidifying capacities of 3 samples were below their claimed values where 1 model was found with dehumidifying capacity of 11.8% below its claim.
The test observed that a great majority of manufacturers were found to have adopted another test condition in their favour to measure the dehumidifying capacity of their products.
Of the 12 samples, 11 also claimed dehumidifying capacity at conditions of 30℃ temperature and 80% relative humidity (RH).
The Council is critical of this approach as it might not accurately reflect the indoor environment when the dehumidifier is operating with the windows closed.
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.
A more realistic measurement of dehumidifying capacity is laid down in the US Association of Home Appliance Manufacturers (ANSI/AHAM) standard for the traditional compressor type, which sets the test conditions at 26.7℃ and RH 60%.
This is the same standard test environment stipulated in the Mandatory Energy Efficiency Labelling Scheme (MEELS) of the Electrical and Mechanical Services Department (EMSD) which covers compressor type dehumidifiers.
Since there are often 2 different sets of capacity claims, the Council recommends that consumers refer to the dehumidifying capacity rating on the energy label when choosing compressor type dehumidifiers. It is measured under standard test environment in accordance with the MEELS.
The manufacturers' favourable test condition is not a standard test condition required by the MEELS; moreover, the problem of over-claims of dehumidifying capacity was widely observed when the samples were tested against their own test environment (30℃ and RH 80%). The results showed that only 1 sample had a measured dehumidifying capacity higher than the claimed, and 6 samples were significantly less than their own claims in dehumidifying capacity, by some 6% to 13.8%.
As for energy efficiency, 1 sample failed to meet the requirements of MEELS. Its energy efficiency was 13.9% below the claimed efficiency, exceeding the acceptable tolerance set by the Scheme. After EMSD's follow-up, the model has been removed from the Labelling Scheme and is not allowed to be supplied in Hong Kong.
Only 1 sample met the requirements of the Grade 1 energy efficiency set by EMSD, but its energy efficiency was not the highest among all samples, since the computation of energy efficiency grade should also take into account their claimed dehumidifying capacity.
1 sample failed to meet the safety requirements set by the international standard（IEC 60335-2-40）for inadequate insulation distances at some positions, which would pose potential hazards of electric shock.
Test results were forwarded to EMSD for follow-up investigation.
Consumers are advised to take heed of the following when purchasing dehumidifiers:
- Choose a dehumidifier according to the size of the living space and the surrounding environment. For example, choose one with a higher dehumidifying capacity when one lives close to waterfront or in a high humidity area, and vice versa.
- Pay attention to the Energy Efficiency Label on the dehumidifier: the higher the energy factor, the more energy it saves. As for dehumidifying capacity, a higher value means a faster dehumidifying speed.
- Dehumidifiers equipped with an automatic humidity control function can save energy and at the same time maintain a desirable humidity level.
- 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.
The Council would like to provide the following recommendations to consumers for the use and maintenance of dehumidifiers:
- Read the user manual carefully before using the dehumidifier.
- Place the dehumidifier on a stable and level surface. Leave some space around the dehumidifier when it is in operation to allow for sufficient heat dissipation. Don't block the air inlet, air outlet, and humidity sensor.
- When the dehumidifier is in operation, keep all windows and doors closed to prevent moisture entering the room.
- Wash the water tank regularly. Remember to turn the appliance off for 10 minutes before cleaning to avoid water dripping. Clean the dust filter regularly to avoid clogging up.
- Cover the dehumidifier with a plastic bag when it is not used for a long period of time to prevent dust falling inside the machine.
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