USB Extension Sockets Need Improvement on Safety Level Over 85% of Models Do Not Comply with the Standards

15 May 2019
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USB Extension Sockets Need Improvement on Safety Level Over 85% of Models Do Not Comply with the Standards

With the widespread use of smart phones and a whole array of other mobile devices, many extension cords now come with USB sockets that can simultaneously charge multiple electrical devices, offering great convenience to consumers.  But a Consumer Council test revealed that safety flaws in these new electrical extension sockets raised concerns.  Of the 15 models of extension sockets with USB charging ports the Council tested, 13 models failed to comply with all the safety test items.  The failure of 1 model did not comply with the legal safety requirements. In fact, the Electrical and Mechanical Services Department (EMSD) had earlier advised consumers to stop using it immediately.  Manufacturers are urged to undertake urgent remedial action to improve the quality and design of their sockets to ensure product safety before launch.

Included in the test were 15 USB extension models, priced between $128 and $299, with 2 to 6 USB charging ports, in addition to 3 to 6 sockets for 13A British plugs.  All USB charging ports did not have independent switches.  6 of them came with a master switch for all sockets while the other 9 had independent switches only for the British plug sockets.  The safety test covered British Standard BS 1363-2 and International Standard IEC 60950-1.  Safety, efficiency and convenience of use were also assessed in this comparative test.  The results indicated wide variations in performance, with overall ratings ranging from 2 to 5 points.

In the safety test, 13 models (87%) were found to have safety issues of varying degrees.  1 model in particular failed to comply with the requirements of the Electrical Products (Safety) Regulations in various ways: there was no fuse overcurrent protection; the rated current was only 10A, lower than the statutory requirement of 13A; and the insulation and conductor cross-sectional area of the power supply cord fell short of the standard minimum statutory requirement for 13A extension sockets.  Upon notification by the Council, the EMSD conducted an inspection and notified the public to stop using the product, as well as 2 other USB extension models of similar design of the same brand.

Unsatisfactory construction was also detected in 7 models.  In 5 models, the sockets could not retain the test socket pins for more than 30 seconds, while in 2 others the sockets were found to have bad contact with the test pins.  The deficiency was due to poor design of the socket metal plates, which may adversely affect the normal use of the sockets.

In the test on protection against electric shock, 7 models were found to be unsatisfactory, as there was insufficient insulation distance between the USB circuit/transformer and the USB output socket, which could be accessed by users, resulting in an increased risk of electric shock. The USB circuit insulation in 3 of the models failed the electric strength test, which was to apply a high voltage of 3,000V across the insulation to test out the strength, insufficient of electric strength will pose a risk of electric shock to users during USB charging.  In addition, 1 model did not have an effective barrier between the earth socket hole and current-carrying conductor, posing a risk of electric shock by direct access to the live metal parts.  

Furthermore, 9 models failed the endurance test for various reasons: substantial breakage of power cord conductor strands after repeated flexing, excessive temperature rise, which prevented completion of the test, damage or melting of the switches due to overheat after repeated operation, and a higher voltage drop measured than the standard limit, which could cause a temperature rise or failure of the switches.  The priciest model ($299) could not complete the socket endurance test after the metal plates were found damaged during the 12,000-cycle plugging and unplugging test. The poorest performing model scored only 2.5 points in the endurance test.

In addition to considering safety and endurance, consumers should take into account the energy efficiency of the products.  The test revealed substantial variations in standby power consumption.  For models with independent switches, when all the switches were on, their standby power consumption varied from 0.134W to 3.28W, a significant difference of 23 times.  The standby energy consumption of the least energy efficient model could amount to 28.7kWh a year.  Assuming a tariff of $1.2 per unit, its annual standby electricity cost alone would reach $34.5.  In contrast, when all the switches were turned off, the standby power consumption costs around $4 per year.  In the case of a model with only a single master on/off switch, when the switch was turned off its power consumption went down to zero.  Even though extension sockets are not high power-consuming products, consumers should always switch them off the sockets when not in use to help reduce energy consumption. 

The energy-efficiency calculations showed the models varied from 60% to 82%.  The prices of the models were not necessarily related to their energy performance.  Indeed, the lowest priced model ($128) recorded 79% efficiency, which was comparatively better than a model twice its price ($298), with only 70% efficiency. 

Consumers using extension sockets should pay attention to the following:

- Each socket should be used with only one extension socket or adaptor; to avoid overloading of the circuit, extension sockets should not be used in conjunction with any adaptors;

- Electrical appliances like air conditioners and heaters should not be powered through extension sockets.  Other domestic appliances with relatively high power consumption are water kettles, electric cookers and large hair dryers.  Electronic products such as computers, TV sets and audio equipment consume considerably less energy.  No multi-socket extension should be loaded with more than 1 appliance that consumes a lot of power;

- Avoid using extension sockets in a humid area, such as a bathroom, or close to water;

- Sockets of irregular shape may offer more convenience to users of electrical products with non-British power plugs.  If the plug pins do not fit well in the sockets, do not use the sockets to avoid damage to the appliance from poor contact;

- When not in use, turn off the switches on the extension sockets.  If the extension is not provided with independent switches, disconnect the socket plug to ensure safety;

- If the extension sockets becomes unusually hot, stop using it immediately. 

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