Technology

Research in the UK has found that approximately 25% of households now have more than seven technology devices in the home, most of which require connection to a TV, and which currently sit within the living room.Increasingly, more homes are looking at the benefits of centrally storing all of this technology in one convenient location, and this will involve some form of rack-mounted or dedicated equipment to house them. 

Most of these products generate heat, whether it's an AV amplifier, Sky box or Apple TV, and are often located i confined spaces where heat cannot easily escape. But why should we worry if the equipment gets a little too hot? Well, for a start, over-heating can affect product reliability. The majority of today's equipment now has more in common with a PC, and incorporates some form of digital processor. Various studies show that the maximum efficient operating temperature for digital equipment is 29°C, and that increases, so the efficiency decreases and more power is required to do the same task. 

Data from a leading hard disk audio/visual server manufacturer for example, shows that a maximum ambient operating temperature of 35°C is recommended, with the motherboard shutting down at 52°C and the central processing unit shutting down at 59°C. 

Equipment failures are not only inconvenient, but costly, both in terms of the cost to replace the hardware itself and also the time spent going back to site - not to mention the goodwill with the client. We must therefore take the cooling of AV equipment seriously if we intend to stay in business over the help force air flow. 

Cooling techniques in racks 

Due to the design and cooling options available, equipment, racks can significantly improve ventilation whilst still enabling kit to be located in a confined space. Vented panels allow air into the racks, vented shelves allow movement of air through the rack, and fan assemblies are available that will help force air flow.

The basics of passive cooling for a rack require that air should be drawn in through the front of the rack, especially where you have front-cooled products such as the Imerge MS1 AV server. The hot air will naturally rise and be dispersed through the top and rear of the rack. The vented shelves and spaces at the rear of the products will ensure that there is sufficient airflow to create a natural movement of air. This movement is obviously dependent on there being a flow of cool air to the front of the rack and therefore front doors are to be avoided where possible.

To help improve airflow, it is possible to mount a fan on the front or rear of the rack to drive air in or out. But to in order to recommend the best solution, we need some hard facts.

Results of thermal simulations carried out by Coventry University

To help us better understand how to cool AV-based equipment racks effectively, my company, AV Racks, teamed up with the Design Institute at Coventry University, who performed thermal simulations using components that are typically found in an AV equipment rack.

Three rack designs were tested:

1. Open rack with only natural convection and no forced cooling.
2. Rack enclosed at sides and rear with the front fully dressed with blanking panels and forced air at front bottom and top rear.
3. Front with blanking panels, side panels but open rear and with forced cooling from the front only.




1) an open rack, 2) a rack enclosed at the sides and rear, 3) a rack with enclosed sides, front blanking panels, front-mounted fans and open rear.

Each rack was populated with the same AV components. From top down, these were an Olson power monitoring PDU, a Sony PS3, two Sky HD boxes, an Xbox 360, a Sony PS3, an Imerge Music Server, an Apple TV unit, two Sonos ZP90s, a Xantech eight-zone audio amp, three Sonos 120s and one Sonos 90, and a Yamaha AV amplifier. The components were positioned with the heavier components in the bottom half of the rack, as is standard practice.

In case 1, heat builds up in the rack, affecting the operating temperature and efficiency of the products, and heat passes from the front of the rack only to feed the air intakes of game consoles and satellite receivers.

In case 2, blanking off the front of the rack was effective in eliminating warm air rising over the front of the rack, and the positioning of a fan system above a hot amplifier was very effective at removing the hot air from that component, however the convection in the rack, even with a top-mounted fan assembly, still allowed heat to build up in the rear centre of the rack.

In case 3, by removing the rear panel and providing additional front cooling for the more prolific heat generating products, the heat dispersal was improved and the number of hot spots reduced.



Comparison of the three racks in terms of hot spots and heat dispersal.

A video of the experiment can also be viewed below:

Conclusion

A dedicated rack can help provide a suitable environment and access to the equipment, but on its own, may not solve the issue of over-heating products. A forced-cooling solution combined with management of the ambient air temperature is essential.

As a result of our work with the Design Institute at Coventry University, we are looking to introduce additional 'spot' cooling solutions within our product range, and to further enhance our direct front-cooled solutions. This work has also led to the following recommendations:

• Equipment will heat confined spaces quickly and cupboard space venting is necessary to maintain a sufficiently low ambient temperature.
• Space at the rear of the rack is critical to allow heat dispersion - ideally this should be a minimum of 50mm to 100mm.
• Front blanking panels should always be used to prevent hot air re-circulation.
• Forced cooling from the front, directed at specific heat generating products, can be the most efficient way to disperse heat in a rack.
• Keeping a rack open at the rear allows for maximum heat dispersion and reduces the hot spots in the rack itself.  

An AV Racks 'Coolracks' front-cooled fan system.

The benefits of effectively managing heat within AV-based racks and furniture is clear: equipment efficiency and reliability are directly affected. The cost of storage and cooling may not be insignificant, but we have to balance this against the much greater cost of call outs, support phone calls and the overall customer experience. We only have to look at the IT industry to see the measures that are taken to cool equipment racks effectively, and these practices are equally important in current-day AV installations.