With winter approaching, while there are not many severely cold days in Hong Kong and most local homes are rather small, versatile bladeless fans with heater function are becoming more popular and more common. The Consumer Council tested 11 models of bladeless fans with heater function on the market, and it was found that the performance varied considerably in terms of the heat-up speed of the heating mode, and the airflow rate and energy efficiency of the cooling mode. During winter, many consumers would turn on the heating mode, yet the heat-up time in the various models varied from 1.8 minutes to 6.8 minutes, a difference of about 2.8 times, of which 2 models took more than 6 minutes to heat up to 90% of the maximum temperature. When compared with the 15 models of traditional fan heaters tested by the Council in 2016, the heat-up speed of the bladeless fans was generally slower. Furthermore, consumers may think that using bladeless fans for heating would save on electricity, but using a bladeless fan with a 2,000W input power for heating as an example, with 5 hours of usage per night at $1.6 per unit of electricity, the electricity cost for one month (30 days) would be up to $480, and in fact for the same heating capacity, using the heating mode in reverse cycle air conditioners (RCACs) would save on electricity when compared with the heating mode in bladeless fans[1]. As for the performance of the cooling mode, the airflow rate of the various models ranged from 5.4m3 to 25.8m3 per minute, a difference of about 3.8 times; whilst the energy efficiency of the cooling mode varied considerably among the various models, with the airflow rate per watt ranging from 0.19m3 to 0.86m3 per minute, a difference of 3.5 times.
The Council tested 11 models of bladeless fans with heater function on the market, of which 6 models came with HEPA filters that claimed to have air purifying functions, with prices ranging from $699 to $6,988 each. The fan motor and fan blades of bladeless fans are concealed in the bottom compartment of the body, and when the fan is turned on, the motor in the bottom compartment would drive the blades to rotate, drawing air into the bottom compartment and pushing air out through the air outlets above the bottom compartment. The tests were conducted by an independent laboratory, with tests conducted on the performance of the heating and cooling modes, standby power consumption, level of quietness and ease of use, etc.
2 Models Took More than 6 Minutes to Heat Up
2 Models Had Uneven Heat Distribution
On cold days, consumers would naturally expect to be able to raise the indoor temperatures quickly. The tests conducted made reference to the latest version of the international standard IEC 60675, comparing the heat-up speeds, the evenness of heat distribution and the power consumption of the various models. 11 models recorded a maximum temperature rise at the hottest spot of the vents ranging from 52.3K to 91.3K (1K is equivalent to 1°C). Furthermore, the heat-up time (i.e. the time required for temperatures to rise to 90% of the maximum temperatures from room temperature) of the various models varied greatly, ranging from 1.8 minutes to 6.8 minutes, of which 2 models took more than 6 minutes to heat up to the corresponding temperatures, whereas 2 other models took less than 2 minutes. The Council had tested 15 models of traditional fan heaters in 2016, and the results showed that the heat-up times of the various models ranged from 15 seconds to 3 minutes, of which 10 models took only 1 minute or less. In comparison, the heat-up speed of bladeless fans on this occasion was generally slower.
If the warm air from the fan is not evenly distributed, it would be comparatively uncomfortable to users. With the models operating at room temperature with no oscillation and at the maximum heating setting, testers mounted 15 thermocouples on a matt black wooden panel, and then placed the wooden panel at distances of 0.5m and 1m from the models, to measure the warm air temperatures of different locations. The tests showed that the average maximum temperatures of the various models were similar, ranging from 34.3°C to 41.5°C. In 2 models, the heat distribution was uneven, with the highest and lowest temperature rise at different locations of the wooden panel varying by up to 20K and 24K respectively when the wooden panel was placed at a distance of 0.5m. Furthermore, when the models and the wooden panels were 0.5m apart, the highest and lowest temperature difference at different parts of the wooden panels was greater than when at 1m apart. From this it could be seen that at a longer distance (1m), the warm air from the fans could cover a greater area of the wooden panels, and hence the heat distribution would be more even. Consumers may wish to consider where the fans are placed when in use, so as to obtain the optimal temperature and comfort.
Energy Efficiency of Heating Modes in RCACs Higher than the Heating Mode of Bladeless Fans
Since the working principle of a heater is directly converting electricity into heat, hence the IEC international standard does not measure the energy efficiency of heater, so consumers should pay attention to a product’s input power (i.e. power consumption) of the heating mode. The tests on this occasion were based on Hong Kong’s voltage of 220V in measuring the power consumption of the heating mode of the various models, and the power recorded ranged from 1,257W to 2,164W. For 5 hours of heating mode usage per night and at $1.6 per unit of electricity, depending on the input power of different models, the power consumption per night would range from 6.3kWh to 10.8kWh, which extrapolates into electricity costs ranging from $302 to $519 per month (30 days). Generally speaking, the higher the input power of the heating mode, the more expensive the electricity costs.
Many consumers may think that using the heating mode of bladeless fans during winter instead of the heating mode of RCACs would save on electricity, but in fact the energy efficiency of the heating mode of RCACs is higher than that of bladeless fans. Therefore for the same heating capacity, using the heating mode of air conditioners instead of bladeless fans would save on electricity.
Airflow Rate of Cooling Mode Could Differ by More than 3.8 Times with Varying Energy Efficiencies
In Hong Kong, most days are warm and hot, leading consumers to use the cooling mode more often. The airflow rate affects the sensation of being “cool and dry”. The tests conducted made reference to the latest version of the international standard IEC 60879, using 4 anemometers to measure airflow rates at the highest fan speed setting without oscillation. It was found that the airflow rate of the various models ranged from 5.4m3 to 25.8m3 per minute, with a 3.8-time difference between the highest and the lowest. 3 models had subpar airflow rates of 10m3 or less per minute, while 2 high-performing models achieved an airflow rate of 23m3 per minute. Overall, 11 models had an average airflow rate of 16.1m3 per minute.
Consumers might expect similar energy efficiencies among these fans, but the results showed otherwise. The energy efficiencies of the cooling mode of the models varied. By airflow rate per minute per watt, it ranged from 0.19m3 to 0.86m3, a difference of more than 3.5 times, with an average of 0.62m3. 2 models achieved an airflow rate of 0.83m3 or more, whilst 3 models with lower performance could only generate an airflow rate of 0.39m3 or less.
Comparing these results to the 12 models of circulation fans tested by the Council in 2023, the average airflow rate of the circulation fans was 15.1m3 per minute, lower than the average of 16.1m3 for the bladeless fans tested. However, the average energy efficiency for circulation fans measured, at 0.73m3 per minute per watt, was higher than that of bladeless fans.
When not connected to Wi-Fi, the standby power consumption of the 11 models ranged from 0.16W to 1.46W. When extrapolated to one month (30 days) the power consumption ranged from 0.1 to 1.1 unit of electricity. 5 models could be operated remotely through an app, but consumers should be aware that standby power consumption would be higher when connected to Wi-Fi.
Electric fans are not at present included in the Electrical and Mechanical Services Department’s (EMSD) Energy Efficiency Labelling Scheme. Even though the power consumption of electric fans is low, according to the results from the Council’s test of circulation fans in 2023 and the current test on bladeless fans, the airflow rates and the energy efficiencies of the models were quite varied. The Council recommends that EMSD may consider including different types of electric fans in the Voluntary Energy Efficiency Labelling Scheme, as energy labelling and performance test values would help consumers compare products and give impetus to manufacturers to improve the performance of their products.
Consumers should pay attention to the following when purchasing and using bladeless fans with heater function:
- When selecting a fan, the heating capacity can be gauged based on the rated input power of the heating mode, and select in accordance with household needs for an appropriate heat-generating product;
- As the input power of the heating mode is generally high, use a separate power socket and avoid sharing with other high power-consumption appliances, and extension cords should not be used;
- Do not use the heating mode to blow dry clothing to prevent fire risks. Keep flammable items such as curtains, carpets, newspapers and miscellaneous items, etc. away from the air vents;
- When using the heating mode, do not let children touch the air vents to prevent burns from the high temperature;
- If there is an anomaly with the fan, such as excessive noise or vibration, or a peculiar smell, stop use immediately and arrange for an inspection;
- Avoid placing fans on uneven floors. Besides ensuring sufficient space for fans to oscillate and to dissipate heat, fans should also not be used inside bathrooms, to prevent electric shock from the inadvertent contact with water;
- Make good use of the temperature setting function of the heating mode to adjust to an appropriate temperature, and only connect to the Wi-Fi if there is a need to remotely operate the fan, so as to save on electricity; and
- If the fan is equipped with air purifying function, the filter should be cleaned and replaced regularly in accordance with the user manual.
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[1] With reference to the record of listed models under the EMSD’s Mandatory Energy Efficiency Labelling Scheme, the heating seasonal performance factor of the latest models ranged from 4.0 to 5.6, i.e. every 1,000W of power consumption can be converted to about 4,000W to 5,600W of heating capacity, whereas bladeless fans can generally only convert 1,000W of power consumption to about 1,000W of heating capacity.