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Thermo Ventilators Test: Significant Variation in Clothes Drying and Room Heating Efficacies – Drying Time Varied with a Maximum of 9 Hours

  • 2017.12.14
Thermo ventilators have found a big market in Hong Kong’s small bathrooms. Besides room heating and ventilation, the device because of its very compact size is also being promoted for clothes drying in the bathroom which is often the case in Hong Kong’s cramped living condition in many households. But according to a Consumer Council test on 10 models of thermo ventilators, their performances in room heating, clothes drying time and energy consumption all varied significantly – by a maximum discrepancy of 26 °C in warm air temperature, 9 hours in drying time, and 7 times in clothes drying electricity costs. In terms of safety, 2 models were found to fail the flame retardant test. Users are reminded also to pay attention to the potential risks of the product.
Included in the test were 3 ceiling-mounted types and 7 window-mounted types ranging in price from $1,880 to $4,800. Both types possess their own advantages and limitations, consumers should therefore choose with care.  The window type samples are small in size, so they can be conveniently installed like a bathroom ventilating fan. Their overall rating (on a scale of 5), however, was mostly 3.5 points or below with 1 model scoring only 2.5 points. The other 3 ceiling samples, though generally more pricey and involving more complicated installation that may require suspended ceiling to conceal the ventilating pipes, their overall rating score was a high 4 points or above.
When comparing thermo ventilators of the same type, their prices do not necessarily fully reflect the efficacy and quality of the device. For example, 2 samples scoring the same overall rating (4.5 points) were priced respectively at $2,580 and $3,980, a difference of 54%.
Clothes drying in 2 to 11 hours
The samples were put to test for their clothes drying time in simulated bathroom environment taking into account Hong Kong's humid weather. The results showed the samples to vary vastly from within 2 hours to over 11 hours, a nearly fivefold discrepancy in drying time. The 3 ceiling types were shown to perform better – all could complete the drying in about 2 hours scoring a rating of 4 points or above. Among the 7 window types, 4 models took more than 6 hours while 1 model took as long as 11 hours 8 minutes, compared with the fastest ceiling sample (1 hour 56 minutes), the difference was more than 9 hours, was rated with a barely 1.5 points. The ceiling types deliver warm air from top to bottom thus providing drying more evenly. The window types, because of the varying distances between the clothes and air ventilation outlet, clothes at the farther end will need comparatively longer drying time.
In terms of clothes drying energy efficacy, the samples were measured for their electrical power consumption in completely drying identical clothes of equal weight within the longest timer cycle. The results showed a wide variation of 0.7 kWh to 6 kWh. Again the 3 ceiling types were found to run up less energy, and in particular the one sample with compressor dehumidifying function was rated as the top performer – the test was based on drying clothes 15 times per month at an average electricity cost of $1.2 per unit (kWh), its monthly electricity bill for clothes drying comes to only $12.6 ($1.2 x 0.7 x15) compared with the model with the highest energy consumption of $108, a difference of more than 7 times.  Consumers are therefore reminded that in the light of the test findings, frequent users of clothes drying should choose a product with lower electrical power consumption to save energy and protect the environment.  
To determine the energy efficiency between thermo ventilators and dehumidifiers, a rough estimate based on the measured input power and electricity consumption can be worked out – the compressor type dehumidifier is the most efficient followed by compressor bathroom thermo ventilators. Those thermo ventilators without compressor and desiccant dehumidifiers would consume more electricity.
Warm air output temperatures vary by a maximum of 26 °C
On room heating, in simulation of cool weather (at room temperature of 5 °C), the samples were tested and measured for their maximum warm air delivery rate and temperature. The results found their maximum warm air temperatures at the outlet to vary from 22 to 48 °C, a substantial difference of 26 °C. On the basis of their maximum warm air delivery rate, only 2 ceiling thermo ventilators, with rating of 4 points or above, were judged to be able to more effectively deliver warm air to evenly fill the bathroom. 
A thermo ventilator uses essentially a ceramic heater to generate heat, and an electrical fan to deliver the warm air. If the heating power reaches 2,000 W or above, the heating capacity of the device will perform better. However, only 1 ceiling sample had heating power of more than 2,000 W, while 1 ceiling type and all 7 window type samples were below 1,500 W. In very cold weather, it is suggested that the bathroom thermo ventilator be switched on to preheat the bathroom before shower.
The test on safety, conducted with reference to the latest international safety standards, found 2 samples to fail to comply with the requirements in needle flame test. The ignited external casing of the samples in question was found to continue burning without being automatically extinguished within 30 seconds. The flame retardant ability of the casing material was considered inadequate and the findings have been referred to the Electrical and Mechanical Services Department for follow-up.
All window type samples' waterproof external enclosure on the outdoor side was in compliance with the IPX4 test against water ingression. 
The test also found in 4 samples when operating under cold air, their measured input power was clearly higher than their rated input power by 8.1% in the highest case. When installing for power supply, users should give due consideration to the potential upsurge in electric current leading to the trigger of the circuit breaker especially in severely cold weather.
Some suggestions for the consumers:
Before purchase
  • Thermo ventilators are not covered in the Mandatory Energy Efficiency Labelling Scheme, consumers can make reference to the product’s rated input power, the higher the input power the more electrical power consumption the device will need;
  • Installing thermo ventilator of a high input power may require an upgrade of the electrical wiring in the main switch box;
  • Take note that the price of some thermo ventilators does not include the installation charges which could run up to over $1,000.  Find out from the retailer the installation cost beforehand.
When in use
  • The IPX4 water ingression protection applies to only the external enclosure on the outdoor side, so do not spray water onto the front panel of the device; 
  • Never place the device in an environment of high temperature or humidity, for instance, right atop of the water heater;
  • Before opening the front panel for cleaning, first switch off the power;
  • When drying clothes, never cover the air outlet with the wet clothes to avoid affecting its safe operation.
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