ENERGY SAVING
Planning for failure
Preparing for the worst when it comes to air handling unit installation/ repairs can prevent future downtime and improve energy efficiency. John Grenville, managing director of ECEX, offers some examples.
T
he well-known scientist, politician and inventor Benjamin Franklin is credited with saying: “If you fail to plan, you
are planning to fail”. This apparently rather superficial quote actually contains an important truth – taking the time to establish an effective strategy increases the chance of business success.
However, the philosophy can also be applied to equipment specification. Indeed, planning for failure (a pre-arranged response for dealing with adverse events) is a constructive response to a potentially catastrophic occurrence that requires visualising the goal and potential obstacles to achieving it as well as how they will be will overcome.
This sort of contingency planning makes solid business sense because it is a form of risk management that can avert catastrophic breakdowns and prevent disruption. A practical example includes replacing old
single-cased fans with multiple high efficiency plug-in ones which not only offer far superior efficiency but also allow for a margin of error – in other words, if one fan breaks down this does not render the entire system useless. As well as introducing a valuable element of redundancy, modernising and optimising existing air handling units (AHUs) to meet the needs of modern buildings also offers the opportunity to upgrade the existing specification by taking advantage of the latest energy
18 January 2021
efficient technology such as EC plug fans and components. And it can extend the service life of the components in HVAC plant and dramatically reduce energy consumption. A prime illustration of this can be found at a major HVAC project involving the refurbishment of a pair of massive AHUs in a large business development at 9 Appold Street in the Broadgate Quarter in London. Both AHUs – one providing a duty of 21 m3/s and the other 16 m3/s – are on the 10th floor of the striking office building. Work completed on the equipment included fan upgrade, chilled water-cooling coil replacement, replacing the large fresh air inlet dampers and installing new ECEX Air Intake screens (which prevent airborne debris before it can enter HVAC systems and block coils and internal filters). General refurbishment was also carried out, comprising corrosion treatment, cleaning, painting, new latches and seals and new lighting circuits. The main logistical challenge in this project was that the installation of the large units was on the top floor of a building accessed by a goods lift that was significantly smaller than the AHUs. Because they were too large to fit into the lifts, this meant that the coils, which were around 3m wide and 2.5m tall, had to be built in kit form in situ. Old, belt-driven centrifugal supply fans were replaced with a high-efficiency plug fan array which increased the effectiveness of the overall
system. So, rather than a single massive fan and motor which, if it failed, would involve considerable expense and disruption, six high efficiency plug fans were fitted in each unit. If one went down, the remaining fans could deliver the same capacity. In engineering terms, this is known as ‘redundancy’– duplicating critical components or functions of a system in order to boost the reliability of the overall system. This form of failsafe relies on adding components. However, there are also circumstances where the opposite – removing components to simplify the system – makes solid business sense. Fewer components, after all, mean there is easier to fix in the event of a breakdown, but there is less to go wrong in the first place.
At the Royal Marsden Hospital in Chelsea, for example, the existing critical fan drive motors were failing. The client also needed to increase air volume due to changes in use in the area served by this air handling unit. Following a detailed survey, a new backward curved direct drive fan was specified and installed complete with 11kW fan motor and inverter. Thanks to the upgrade, the client benefited from higher volume, and reduced maintenance time and costs due to elimination of belt drive, as well as lower energy consumption and life cycle costs. The new drive fan also allows for
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