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Manufacturers taken to task for unrealistic dehumidifying capacity rating - CHOICE # 400

  • 2010.02.12

The Consumer Council has taken manufacturers of dehumidifiers to task for inflating the dehumidifying capacity of their products unrealistically.

This followed a test on 12 dehumidifier samples comprising 8 models of the compressor type (with claims of capacity ranging from 14L to 18L of moisture a day), 3 models of the desiccant type (with claims of capacity of 6L a day), and 1 model of the hybrid type (with claims of capacity of 12L a day).

In the test, all manufacturers were found to adopt test conditions in their favour to measure the dehumidifying capacity of their products.

Of the 12 samples, 9 based their rating of capacity at conditions of 30℃ temperature and 80% relative humidity (RH). The other 3 samples were based on 32℃ and RH 80%, or 30℃ and RH 85%.

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 Voluntary Energy Efficiency Labelling Scheme of the Electrical and Mechanical Services Department (EMSD) which covers compressor type dehumidifiers.

The problem of over-claims of dehumidifying capacity was observed when the samples were tested against their own test environment (30℃ and RH 80%). The results showed that half of the dehumidifier samples (6 out of 12) were less than their own claims in capacity, by 5% to 16%.

The Council has forwarded the findings to the Customs and Excise Department for any follow-up action deemed necessary.

The samples were also tested against the standard test environment (26.7℃ and RH 60%).

The results when measured against the actual capacity based on the manufacturers' commonly used test environment, notably for the compressor type and hybrid type, showed that the discrepancy could be as high as 1.5 times.

In addition to dehumidifying capacity, the samples were also tested for energy efficiency.

At standard test environment (26.7℃ and RH 60%), the energy efficiency of the dehumidifiers varied substantially with the biggest difference reaching nearly 3 times.

Generally, the compressor type samples were more energy efficient than the desiccant type samples, with the hybrid type samples somewhere in between.

On safety, 5 samples were found to be less than entirely satisfactory in all safety test items. But the EMSD has advised that such minor deficiencies should pose no safety hazards in normal operation.

Consumers are nevertheless advised to use with due care; and do not forget to unplug the dehumidifier before cleaning the appliance.

For more details on their performance, consumers can refer to the test report in CHOICE.

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