Around 30 percent of installed fans fail to meet the tightened energy efficiency requirements of the European Ecodesign Directive (2009/125/EC), which came into effect in 2013, and a further 20 percent will fall short of even tougher standards that will apply from 2015.
Packing density in enclosures is increasing and this is spearheading the need for more powerful cooling systems. Combined fan-and-filter units, using ambient air, are a particularly cost-effective method of combating these increasing thermal loads should operating conditions permit their use.
Against this background, Rittal has developed a range of fan-and-filter units, incorporating EC technology called 'TopTherm'. This product, equipped with powerful diagonal fans, along with smart control and monitoring functions, provides switchgear manufacturers and users with a viable option for cooling enclosures, offering a high level of energy efficiency and security.
Compared with conventional fan-and-filter units, which use ac shaded-pole motors, Rittal’s EC units employ brushless dc motors that are two-and-a-half times more efficient. Energy savings of up to 63 percent over a standard ac fan-and-filter unit can deliver a significant reduction in annual operating costs; for example, savings of over £500 may be possible in a standard production facility using 100 fan-and-filter units.
Further savings can be made by changing the air throughput to suit the actual demand. Integrated conversion (commutation) of ac to dc allows the speed of the motor to be controlled using a voltage regulator which, in turn, permits continuous fan speed control via an integrated interface.
The fan can be controlled using 0-10Vdc or a pulse width modulated signal, either via Rittal’s EC speed control sensor or a programmable logic controller. Requiring no additional power supply, the optional EC speed control sensor has a fixed set-point temperature of 35°C.
A tachometer signal output enables the fan speed to be monitored and hence its operating condition determined. This can be used to alert a supervisor immediately to any faults or failures, ensuring a timely response before the temperature in the enclosure exceeds a defined threshold. Such actions minimises the risk of installed component failure due to excessive temperatures inside the enclosure, increasing the overall reliability of the system.
With blades shaped so that air is blown outwards, diagonally from the fan, TopTherm offers enhanced performance over previous models. This is evident in the performance diagram shown on page XX; a steeper air throughput curve - and hence a higher installed operating point - is achieved compared with conventional models.
In practical terms, the fan profile ensures an air volume flow rate that is more stable with changing system pressure, as well as a consistently higher air throughput and a longer service life for the filter mats.
These advantages are particularly significant in the event of high resistance to air flow, caused by high packing density or clogged filter mats, which normally lead to a reduction in air throughput. In addition, the diagonal flow ensures better air distribution. Preventing hot spots creates a more consistent temperature throughout the enclosure,
Thanks to the higher air throughput and better air distribution within the enclosure, temperature based control reduces fan operating hours by up to 40 percent compared with the running time of conventional fan-and-filter units. Proven in tests, this lower running time correspondingly increases the service life of a unit. It also translates into lower maintenance, as the filter mats need to be replaced less frequently.
Efficiency comes in many guises and not only applies to electrical energy, but also to manufacturing processes. Rittal’s fan-and-filter units can be installed without tools, maximising efficiency on the shopfloor. As well as a simple, snap on installation system, changing the air flow direction and position of the electrical connections are equally straightforward.
The same applies for changing filter mats, which are located behind a louvred grille. This grille can also be opened without tools: it can be unlatched with a single finger and tilted forwards, remaining attached at an angle of around 70 degrees. Last but not least, replacement units may be fitted simply and quickly as the cut-out for the TopTherm fan-and-filter units is exactly the same as for Rittal’s previous models.
Rittal EC TopTherm fan-and-filter units deliver a volumetric flow rate in the range 55 to 900 m³/h at an operating voltage of 230Vac 50/60Hz. This opens up new opportunities for switchgear manufacturers and users of energy efficient climate control.
If an application requires a significantly greater air throughput then TopTherm fan-and-filter units still afford a convenient means of achieving it, as multiple units can be installed side-by-side.
For especially demanding environments, the protection class can be increased to IP56 with optional hose-proof hoods. These are easily cleaned from the outside and are fitted with the same sealing material as that used in Rittal’s popular Hygienic Design products.
For sensitive applications subjected to high levels of electromagnetic interference, Rittal’s EMC TopTherm fan-and-filter units have all the advantages of the standard range, as well as satisfying performance level 2 for shielding according to EN61587-3:2006, in a frequency range of 30 to 1,000MHz.
The minimum shielding for the frequency ranges 30 to 230MHz and 230 to 1,000MHz is 40dB and 30dB respectively. The housing and filter mat are designed to provide maximum EMC protection and, as a result, the user no longer needs to resort to a grille for shielding. The EMC fan-and-filter units have an air throughput range of 20 to 900m3/h and the available protection categories extend from IP51 to IP54.
Christian Westwood is with Rittal