What makes an enclosure NBN-compliant?
Several manufacturers have turned to making enclosures specifically for the NBN, but what does it take to be compliant? Callum Fitzpatrick reports.
With the National Broadband Network (NBN) rollout firmly underway, there is inevitably a demand for enclosures to house equipment. Not only to keep the network termination device (NTD), universal power supply (UPS) and any other data communications components neat and tidy, but to optimise performance and keep gear protected from accidental damage and dust.
Requirements have been put in place by NBN Co to assure that these enclosures are compliant and therefore conducive to the operation of any technology that is installed. This has been outlined in Residential Preparation and Installation Guide: SDUs and MDUs.
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Three major considerations lie at the heart of the document. These are: the size of the enclosure, available space around internal equipment and the level of ventilation.
The guide requires that an enclosure (named a home distributor) must have a minimum internal volume of 20L (20,000cm3) and the minimum surface area of mounting required for an indoor NTD composite layout is 2,000cm2. Additionally, the minimum available depth of a home distributor for mounting NBN Co equipment is 10cm, providing a minimum 2cm clearance between the NBN Co equipment and the door/cover.
It is also specified that enclosures must provide unimpeded air circulation and should be installed in an area with a bulk space of at least 1,000L in volume, such as a wardrobe, large room or, as most commonly used, a garage.
Heat is inevitably a major concern with any electrical equipment and the relationship between the long term operating temperature of a device and its lifespan is plain to see. NBN Co estimates that for its equipment, failure rates double for every 10ºC rise in the long term average temperature within an enclosure.
According to Residential Preparation and Installation Guide: SDUs and MDUs:
“To reduce the chance and frequency of equipment failure, it is important to optimise an equipment enclosure’s ability to dissipate heat. This in turn reduces inconvenience to the end user, productivity – loss, and the costs involved in managing failures and restoring services. For these reasons, the design of an open enclosure or home distributor should be optimised to take advantage of convection cooling.
“Convection currents established in the air within and around the enclosure carry heat away from the equipment, minimising temperature rise in the electronic equipment it houses. Effective convection requires enclosures to be thermally ventilated.”
As such, NBN Co has outlined a series of rules for the ventilation of an enclosure.
Jared Smith from Built Boards, a specialist in electrical switchboards and enclosures, says the NBN Co’s requirements were put in place as a response to installers who were experimenting with unsuitable products.
“Some of the enclosures that were being installed were ok, but many of them weren’t suited to NBN equipment,” he says. “As such, NBN Co released a set of initial guidelines; however, these were too broad and open about the type of enclosure that was appropriate.
“Following this, NBN Co has fine-tuned the document, making the guidelines much more strict.”
Jared explains that if an enclosure is deemed incompliant, NBN Co will refuse to install its hardware.
“I’ve already heard of different instances where an NBN installer has arrived at a jobsite, realised there’s not enough space inside an enclosure and simply mounted all the hardware next to it. This obviously defeats the whole purpose of the exercise in the first place.”
Grove Communication Supplies, an Australian-owned and operated wholesaler of data and communication products, recently released its NBN Co compliant Grove Express enclosure. The company’s project development manager Doug Crockett says that when it comes to performance and safety, ventilation is paramount.
“The NBN equipment’s lifespan can be halved if the enclosure doesn’t have the correct ventilation. What’s more, due to their nature, batteries within the UPS can emit a combustible gas, which poses the risk of explosion.”
This danger is compounded if the enclosure is installed in a room that is exposed to high temperatures.
“If you’re dealing with a single brick house, you can’t place NBN equipment on a north or western-facing wall inside the dwelling.
“When a double brick building is concerned, you can install on these walls, but you need to fill the wall cavity with an R1.5 or higher rated insulation batt.”
That’s why the Grove Express enclosure includes an air pocket behind the mounting plate – the NBN equipment is buffered away from the wall, reducing solar loading from the outside of the house, giving additional options as to where users can request equipment to be provisioned.
Doug adds that when it comes to choosing the right enclosure for the job, it’s not about simply finding a box that can house the NBN equipment – an enclosure should be more than that.
“An enclosure isn’t just a metal box – it’s really a landing platform that simplifies the NBN installation for everybody involved. It makes it easy for the end user to manage their equipment and it allows contractors to be certain that they’re carrying out a compliant install.”
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