Feature Enclosures
Chris Lloyd, sales and marketing manager for Spelsberg UK, explains the strengths and weaknesses of different cable entry options when specifying enclosures and provides details on the latest developments
hen specifying an enclosure for electrical applications, one of the key considerations has to be cable entry. The cable
entry points of an enclosure help to determine the level of ingress protection (IP) provided against the external envi- ronment as well as cable retention force and crucially, installation speed, all the while balancing utility with cost. Recent developments in materials, moulding technology and push-fit grommets have
Push fit cable entries Push fit cable entries have become increasingly popular as plastic mould- ing technology has advanced. Enclosure manufacturers regularly use two types of material moulded into one box, pro- viding rigidity in the walls and soft, flexible membranes to allow cables to be pushed through, but still offer a good IP rating that protects from moisture as well as physical intrusions. However, the cable retention force on offer is lower than with other alternatives. If an enclosure is going to be used in a
changed the options that are available, providing a more specialised solution for various applications. Making the right choice of enclosure
and entry method can make the differ- ence between a profitable job and a loss, as well as guaranteeing the all important safety of installers and end users. With new ‘moulded-in’ entry
methods now on the market, offering extremely fast entries, and traditional cable glands being replaced in some instances by lower cost fast fit grom- mets, it is essential to know when to specify the right solution for any given application. For example, by far the most common
cable entry method is traditional cable glands fitted to the body of the enclo- sure through knock-outs. While this option offers a safe choice, what a lot of people don’t realise is that they are often over specifying and this can mas- sively increase costs and installation times, as well as making maintenance more time consuming at a later date.
clean, dry and well insulated environ- ment, only lower levels of IP are needed. In these situations both the enclosures and wires are likely to be well secured in their position so there is little need for high cable retention. If there are a number of enclosures to be wired then using cable glands will be extremely time consuming and unnecessary. Many enclosures are available with a
flexible membrane which provides a seal simply by pushing the end of the cable through the centre nipple. As the membrane stretches, the point of great- est extension opens and allows the cable through. The inverted seal grips the cable and provides a fast entry seal. As IP and cable retention are not large con- cerns, this method is ideal for reducing installation times and costs. In the event that re-wiring is required in the future, the old wire can simply be pulled out and the new wire inserted.
Grommets There are a number of membrane plug/grommet products available that offer good sealing up to IP67 that are fast to use. As a grommet, they are a push fit design both to install and to feed the cable through. Recent grommet designs will allow for a variety of cable/conduc- tor widths and are resistant to vibration. There are fast-fit grommet seals available that clip into standard drilled and
The Ultimate in customised enclosures
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How to make an entrance W
Above, left and below: making the right choice of enclosure and entry method can make the difference between a profitable job and a loss, as well as guaranteeing the all important safety of installers and end users
knockout holes that provide positive cable retention.
Cable glands (clamping) Despite the advantages of quick fitting seals and grommets in many applica- tions, there are still some situations where the most appropriate cable entry method is the clamped, dome-top, cable gland. A number of variations of this type are available in both nylon and metal but the salient features that ensure superior performance to the traditional stuffing gland are in its construction. The cable is fed through a sealing ring
which is placed in an ‘iris’ that closes onto the sealing ring, clamping the cable and forming a high IP seal as the dome top is screwed down. This forms an IP68 seal around the wire, meaning that the enclosures can be fully submerged with- out fear of ingress, as well as creating very high cable retention, alleviating any risk of connections failing due to pres- sure on the wire.
Conclusion In reality there are many different cable entry options available, all of which carry different benefits to the user. Choosing the correct solution can save money and time at the point of installation and during future maintenance. When specifying for a specific application it is a good idea to speak to an expert who can recom- mend the ideal product.
Spelsberg
www.spelsberg.co.uk T: 01952 200 716
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For further information please contact: tel: 01642 604 400 email:
sales@fibox.co.uk web:
www.fibox.com
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