The big match

EMC: We’ll start with the big question first. Which is the best – perforated or wire mesh cable tray?

EG: Unlike certain companies that manufacture just one of these solutions, and therefore happily push the benefits of one over the other, we, as a company that manufactures both, are able to provide a non-biased viewpoint.

Unfortunately, this doesn’t automatically help to give a clearer picture as both are perfectly acceptable solutions and both are covered by the same European standard for tray and ladder (IEC 61537).

Instead, the decision of when to use one rather than the other is dependent on the installation. As a result, the question that needs to be asked is not, “Which is the best?”, but rather, “How do I choose between the two?”

One of the first arguments often made in favour of wire mesh cable tray is that it is cheaper and quicker to install, but this isn’t always the case.

For example, if an installation requires numerous straight lengths, perforated tray is the best option. It’s generally stronger and so only needs supports every 2-2.5 metres, rather than the 1-1.5 metre intervals that wire mesh requires. With fewer cantilever arms or trapeze hangers to fit, installation time and cost is significantly reduced.

Conversely, should the installation be in a confined space with numerous twists, turns and obstacles to cope with, wire-mesh tray is cheaper and quicker to install due to the ease with which it can be configured onsite without the need for factory-made fittings.

However, this task needs to be undertaken by experienced installers to avoid potential problems such as sharp edges caused by poorly cut and poorly installed fittings.

Then again, if an installation comprises a large number of identical bends and tees, perforated tray would be better than wire mesh on the basis that it is easier and quicker to install bespoke factory-made fittings than cut them all to size onsite.

EMC: Can factory-made fittings be used with wire-mesh cable tray?

EG: The key concept behind wire-mesh cable tray is that it is installed using bespoke accessories that are made onsite, resulting in savings during installation. That said, some manufacturers do supply factory- made bends, tees and risers for wire-mesh tray, although this approach is normally reserved for perforated tray.

EMC: Can the same type of cables be installed on both solutions?

EG: Both types of tray are suitable for power and data cabling. But, when installing power cables, these need to be fitted to either system with steel wire armour or a second sheath of PVC-U as both give cable support, rather than full mechanical protection.

As a rule of thumb, wire-mesh tray tends to be used for data cabling and other light signal cable work, and is likely to be found in applications where the installation is in a false ceiling or cavity floor. In installations that are accessible to the general public, and therefore at risk of vandalism or accidental damage, perforated tray has the advantage over wire mesh.

Perforated tray provides greater physical protection for the cables and is secured with screws, which are harder to vandalise and less likely to be accidentally dislodged than the quick-fit tabs used to secure lengths of wire-mesh tray. Of course, the use of screws does mean perforated tray takes slightly longer to install, which can lead to wire mesh being selected ahead of it in situations where budget and deadlines are tight.

Going back to cable types in relation to tray solutions, how different types of cable are secured also needs to be addressed. In most instances this can be achieved to a suitable standard through use of cable ties, but this approach becomes unsuitable when larger cables, such as three-phase power cables, need to be carried on a tray system.

In such situations there is no choice but to secure the cables with specially manufactured cleats, which need to be fixed securely to an already rigid system. And at this time, the use of cleats on wire mesh tray does not provide an adequate level of support in terms of both fixing and the rigidity of the system.

Wire mesh does have the advantage over perforated tray when it comes to ventilation. Its design allows for better air circulation, thus reducing the array of potential problems caused by overheating cables.

EMC: Are the different types of finish commonly associated with perforated tray also available for wire-mesh tray?

EG: Wire mesh is most commonly supplied with an electro-plated finish, which is similar to the standard pre-galvanised finish of perforated tray. Both systems can also be supplied in stainless steel or hot dipped galvanised finishes for more aggressive environments.

It’s only when a system is installed in an area where corrosion will be very high, such as heavy industrial or marine environments, that a difference between the types of finish available for the different trays becomes significant. In these scenarios, perforated tray can be given a thicker galvanised coating – deep galvanised – that uses special sheet steels that can provide a galvanised thickness of at least three times that normally used – a solution that gives an extended product life three times that of a standard hot dipped galvanised product and up to six times that of electro-plated wire-mesh cable tray. All of which means, the more aggressive the environment, the more suitable perforated tray is, because it can be given a deep galvanised finish.

EMC: What advice would you offer a firm torn between wire mesh and perforated tray?

EG: The choice between the different tray solutions isn’t always black and white. My advice would be to talk to a company that offers both so that you know what they suggest will be the best installation solution.

Legrand manufactures both wire-mesh and perforated cable tray. Its Swifts SW steel wire cable tray was launched earlier this year with the aim of being unbeatable for strength, speed and flexibility. It features a selection of supports and fixings, a slot and tab system that enables tray to be secured directly to fittings without the need for additional fixings and a choice of finishes that make it suitable for use in most environments.

Meanwhile, its Swifts range of perforated tray features light, medium and heavy-duty return flange, all of which are available in a variety of finishes, thus ensuring the range is able to provide a full spectrum of system solutions.