Wiring a panel? Identification is the key to good management
06 September 2010
The identification of wiring, terminal blocks and components is crucial to any panel building project. Clear identification will help with future maintenance and reconfigurations, while offering reassurance to those responsible for health and safety. John McGee looks at the available options
Cable management is an important aspect of panel building, but quite apart from good cable routing and installation, one of the most important considerations is cable identification. Correct and clear identification offers benefits in both the short and long term, and modern cable management technology offers panel and system builders a wide range of marking options to suit their particular projects, the operational conditions that will prevail when they are in service and standards that have to be met.
First and foremost, there is a need to consider which materials are appropriate to the application. Identification markers are now available in a variety of materials to meet requirements such as zero halogen (HF) and limited fire hazard (LFH). Cable management products that meet HF and LFH restrictions are tested for toxic smoke generation, flammability and flame propagation to ensure that, in the event of a fire, fumes from burning electrical installations are not a threat to public safety.
One method that the panel builder might care to consider for cable identification is heatshrink sleeving. For those installations where it is necessary to identify a variety of cable sizes, 3:1 heatshrink sleeve is recommended, as it covers a good range of diameters. With shrinkage, these sleeves provide permanent marking, so there is least risk of removal, either by accident or as a result of tampering. It is also advisable to use a product that has good resistance to solvents and chemicals, as this will ensure the cable markers are protected should they be exposed to these products. An added advantage of heatshrink tubing is its ability to work in extreme temperatures. There are products available that will tolerate temperatures between -55 and +135oC, for example.
An alternative to heatshrink sleeving is to use a marker system comprising rings printed with different colours, letters or numbers. These are simply threaded on the cable in a sequence that forms a text or numerical legend. One such system is HellermanTyton’s chevron cut marker system, HelaGrip, which is pictured below. The chevron shape ensures that the individual rings stay locked together so the text or number remains aligned. While not providing the same level of protection as products that are HF and LFH compliant, products from reputable manufacturers are generally made from high grade PVC, which is both durable and affordable.
If the panel is to be located in an environment that poses low risk or where there is no issue of public safety, simple coloured cable ties may provide an adequate and cost-effective solution to the problem of cable identification. For example, a three phase panel might use blue, grey and black cable ties to mark each phase. This would make them identifiable at a glance, making it easier for anyone to carry out future maintenance on the panel, which could potentially help to reduce downtime.
For those who want to speed up the process of using identification markers, there are methods available to facilitate onsite printing. Thermal transfer desktop printers, such as the one illustrated below, are ideal for this purpose. Using onsite printers means markers can be produced as and when required, as opposed to waiting for a third party to manufacture labels and then ship them to site. Thus last minute work can be completed, or changes can be accommodated at short notice, which in turn reduces downtime and can help save money.
For easy identification of circuits, coloured partitions can be used for rail mount terminals. These are separate elements on the terminal board, which ensures that circuits are clearly visible. An added bonus is that the insulation distances will be increased between terminal blocks. And again, as is the case with other systems described in this article, easy identification will ensure that maintenance and any future re-work will be faster and more straightforward.
It may be that for some, cable identification does not rank highly in the list of priorities that defines a typical panel building project. In this author’s view, it would be a mistake not to give due consideration to this area and give it the scrutiny it deserves.
The best advice is to take all your components into account when choosing the right marking methods and apply the same diligence to the cables as you do to the larger elements. By choosing the best materials and methods for each application, the panel builder can be confident in the knowledge that his work will be appreciated by the end-user when the time comes to conduct maintenance or re-work, at which point convenience and safety take top priority.
John McGee is product manager, identification and protection at HellermannTyton
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