Fans are the ultimate quick fix

Flakt Woods, Fans, AHUs
The opportunities of planned replacement — Andy Cardy.

For facilities managers looking to improve overall building efficiencies, replacing commercial fans can be an excellent and potentially lucrative option. Andy Cardy of Fläkt Woods explains the benefits on offer.

Twelve years from now, there will be 70% more construction going on around the world — according to the latest figures from the Global Construction 2025 forecasts published in July. And the statistics for the UK are equally fascinating, with a predicted growth of 2.1% a year on average until 2025 — twice the rate of the western European average and far removed from the bad news that has dominated headlines in recent years.

Of course, along with the increases in construction output, energy efficiency in commercial properties will also improve as they continue to utilise the latest technology.

But while this is all well and good in new buildings, millions of existing commercial properties still remain —requiring drastic attention and, in some cases, quick fixes to improve efficiencies and energy consumption,

Effective retrofitting of ageing and inefficient equipment — whether it is the heating plant, air-handling units, or cooling system — is a market that hasn’t always been optimised. And that’s possibly due to many upgrades of old equipment coinciding with breakdowns and distress purchases, rather than as part of an ongoing plan of improvements.

However, when building and facilities managers examine the potential payback from effective retrofitting, the monetary benefits really start to stack up — and none more so than for commercial fans.

The 93% efficiency of replacement fans for 40-year-old units having an estimated efficiency of 76% at Western General Hospital in Edinburgh is expected to achieve a 2-year payback based on running costs.

Most industry professionals will already be aware that there have been significant changes in the manufacture of fans in recent years, mainly being driven by ErP Directives.

These are designed to improve fan efficiencies and, on the whole, have gone a long way towards reducing commercial-fan running costs. European Commission Regulation EU No. 327/2011, which came into force in January 2013, applies to all fans driven, or designed to be driven, by electric motors with an input power of between 125 W and 500 kW. It specifies minimum fan/motor efficiencies for all fan types and installation categories, regardless of whether they operate as an individual unit or as a component within a device.

Manufacturers now have to use a combination of the latest motor technology, aerodynamically optimised configurations and tightly controlled manufacturing processes to improve the overall efficiencies of their products.

And this is just the tip of the efficiency iceberg.

The European Commission has a clear intention to continue to tighten regulations, as indicated in the second tier (January 2015) of the ErP Directive.

The second tier requires further efficiency improvements, which will certainly prevent the sale of many products currently on the market today.

And this isn’t the end of improvements, with additional revisions planned in 2017 and 2019, which will raise the bar even higher.

So what do these latest standards mean for retrofitting of fans in commercial applications? Potentially, they could result in huge reductions in energy costs, as illustrated by the following examples.

Take, for instance, a 3-stage axial fan installed 40 years ago into a commercial ventilation system and having an absorbed impeller of 85 kW — for the complete 3-stage unit. Its motor is probably, at best, 76% efficient and will require an input power of about 112 kW.

A new replacement fan will have an impeller with a better aerodynamic performance, so its absorbed power might be 58 kW for the complete 3-stage unit when run at 40 Hz via an inverter. The motor might be 93% efficient, so the input power would be around 63 kW translating into a 44% reduction in energy usage.

Modern axial fans, such as the JM aerofoil from Fläkt Woods, have an efficiency of 93%.

The overall power consumption is reduced by around 44%. In addition, when replacement fans are coupled with inverter drives, running costs can be reduced by a further 10%.

When these energy reductions are converted to hard cash, the payback can be particularly impressive.

The potential for savings was demonstrated by a recent installation at Western General Hospital in Edinburgh, where the replacement of six units with JM axial fans (from Fläkt Woods) provided a payback of less than two years — not to mention saving hundreds of tonnes of carbon as an added benefit.

Another consideration when trying to improve fan efficiencies is to upgrade controls. In many cases, controls used with ageing fans don’t allow flexible use of the system, which often results in fans having to run at full capacity 24/7. Clearly, this is not only inefficient, but also potentially problematic for servicing and maintenance schedules.

When retrofitting replacement fans, it is also important to complete a thorough check of the existing control packages and/or building management system that might be in place. This simple step will help maximise the potential of a new system and improve the payback period.

All in all, retrofitting commercial fans, especially those which have been in use for decades, is a highly effective way of reducing building running costs.

As large commercial properties often have several units installed on site, their combined potential running-cost saving (especially if used with inverter drives) and much reduced payback period, make them obvious targets for upgrades. Doing so will ensure existing commercial buildings can benefit from the latest technology.

Andy Cardy is product manager with Fläkt Woods.

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