Dangerous compatibility

Mark Flanagan, technical manager with Scolmore Group looks at some of the problems associated with inferior quality connector products which don’t meet the required standards and therefore represent a safety hazard.

Since we introduced our first ever Flow Connector in 2007, it has proved a highly popular product and we have continued to grow and develop the range. Inevitably this has led to a lot of copies of the product being brought to market. They may be cheaper, but in many cases they are of inferior quality and don’t meet the relevant standards. We have heard reports that other manufacturer’s connectors can plug into our connectors. This may be the case, but is not safe.

Connectors are a method of joining one conductor to another and are capable of passing larger currents and voltages. A poor connection passing such currents can cause high resistance faults which could generate enough heat to degrade insulation which in turn can lead to a breakdown in the circuit and, in extreme cases, result in fire.

In light of this recent influx of inferior copies we would like to draw attention to the inter-compatibility of connectors and look at some of the standards that installation couplers should be conforming to, as well as some of the associated dangers and risks.

Standard IEC EN 61535 – relates to the installation of couplers intended for permanent connection in fixed installations. Clause 9 focuses on dangerous compatibility.

Clause 9.1 An installation coupler system shall be designed and constructed so that unintended or improper connection is prevented.

It should be noted that unintended or improper connections include single pole connection, except for earth-to-earth connection. Compliance is checked by inspection and the following test. It shall not be possible to insert the installation male connector into the installation female connector resulting in a dangerous situation. Engagement of the installation male and installation female connector is attempted in any unintended configuration using a force of 80 N for installation couplers marked as 10A, 16A, 20A; or 120 N for installation couplers marked as 25A and 32A. The force shall be applied on the same axis of the connection for one minute during which time the installation male and installation female connector contacts shall not engage.  

Clause 9.2 It shall not be possible, within a given installation coupler system, to engage an installation male connector with an installation female connector:

-       with a different number of live poles; exceptions may be admitted for installation female connectors which are specially constructed for the purpose of allowing engagement with installation male connectors of a lower number of poles, provided that no dangerous situation can arise;

-       without earthing contact if the installation male connector is an installation male connector with earthing contact;

-       with different phase to neutral voltage ratings or different rated currents

Compliance is checked by the test according to 9.1.

Clause 9.3 Installation couplers of different systems from the same manufacturer shall not be dangerously compatible. Compliance is checked by the test according to 9.1.

Clause 9.4 Installation couplers according to this standard shall not be compatible with systems specified in standard sheets of IEC 60309, IEC 60320, IEC 60906 and with the national household plug and socket-outlet systems of the country where the product is placed on the market. Compliance is checked by manual test and in case of doubt by examination of drawings.

Our unique Flow connector is designed to prevent unintended or improper connection.

Incorrect polarity of connections could be considered as unintended or improper connection and could result in a dangerous situation. If the polarity of a connection is incorrect then the appliance/fixture connected, will either not work, resulting in time spent fault finding or, in some cases, appliance/fixtures can remain live, even if the power switch is turned off to them.

Clause 12 of the standard deals with Construction.

Clause 12.10 Installation couplers shall be provided with retaining means which engages automatically when the installation coupler or cap is connected and which is capable of disengagement for disconnecting. It shall only be possible to render the means of retention ineffective by a deliberate or intentional act. For installation couplers classified in accordance with 7.4.1 intended for installation in a readily accessible location the means of disengagement shall only be made by the use of a key or tool.

Compliance is checked by the following test: The fully engaged installation coupler shall be subjected to a smooth axial traction force of 80 N for a period of one minute, during which the retaining device shall be fully engaged. The installation coupler shall not loosen or become disconnected.

Should the installation coupler loosen, this may result in the earthing integrity of a circuit not being maintained. In the unfortunate event that something goes wrong - such as a short or fault with an appliance - it may be possible to expose someone to a serious shock hazard, as it may impair or prevent operation of protective devices in the circuit.

We have highlighted some of the standards that installation couplers should be conforming to. Safety is a critical market requirement and it is vital that manufacturers identify the required regulations and develop products that meet the required standards. All of our products are independently third party verified to provide the reassurance and confidence that the products being sold or installed are safe and fit for the intended purpose. Not all manufacturers can say the same.

Article can be found here: https://professional-electrician.com/technical/dangerous-compatibility/?utm_source=newsletter&utm_medium=email&utm_campaign=07-Feb




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