Fan-coil units take advantage of new technology

Ability Projects, fan coil units, air conditioning
Fan-coil units as one of the most effective air-conditioning solutions available — Peter Lowther.

The age of the super-intelligent fan-coil unit is almost upon us. Peter Lowther traces recent developments and looks to the future.

Fan-coil development has never been as fast paced, exciting and relevant as it is today. Fan-coil units first became popular in the mid-1970s, and very little changed until around 2002/3.

Of course, superficially they had become more refined but, their ability to air condition a space was little better than 30 years earlier. Then EC (electronically commutated) fan motors arrived on the scene, and everything changed.

EC motors are the portal through which all subsequent fan-coil development has been empowered. Without EC motors, fan coils would almost certainly be fading into obscurity, but, conversely, EC motored fan coils are new, fresh, contemporary and offer plenty to shout about.

EC motor/fan combinations scored highly on two counts: their inherent efficiency at slower fan speeds and their ability to be speed controlled through a 0 to 10 V signal. The efficiency gave EC fan coils their new lease of life in this energy-conscious world, but it is their controllability in which their future lies.

At Ability Projects, our variable-air-volume fan-coil strategies were an obvious first step, but these have been dwarfed by our current plans and ambitions. We now have fans that set their own air volumes and self-balance between ducts. Our current developments include looking at fan coils operating in groups rather than individually. It really is exciting stuff.

Having exploited the fans the next product to be allied to fan coils was the 2-port pressure-independent valve. These devices bring tremendous advantages to fan coils (and other products for that matter) by removing the influence of variations in system pressure and therefore allowing design water flow rates to be preset off site. The current problem is that all these valves have a manufacturing and installation tolerance, which is rarely coincident with the specified flow-rate tolerance — so there are one or two niggles yet to be ironed out, but we will get there.

Our solution is a pressure-independent valve that self checks the water flow it is passing and then self-corrects its positioning if an adjustment is required. This might sound a distant dream, but the reality, I can assure you, is not far off.

There has been a common misconception that chilled beams and chilled ceilings, unlike fan coils, were better placed to work with higher chilled-water temperatures. Where did that come from? The fact is that fan coils are as able to extract the same amount of cooling energy from higher water temperatures as any chilled beam can. The only concern might have been coil pressure drops being too low, but all manufacturers have special arrangements that deal with this.

Our next development ‘on the boards’ is to produce a fan coil that can automatically adapt to changes in chilled-water temperature. Throughout the seasons, therefore, your plant will deliver what is most appropriate (or efficient), and the fan coils sensing the change will adapt their own water flow rates and, possibly, airflow rates in sympathy. Again, a distant dream? Maybe not!

Ability Projects, fan coil units, air conditioning
Fans driven by EC motors can be controlled to deliver the required airflow at the required pressure to each duct.

In the midst of all this excitement, the core features of the fan coil should not be forgotten. Fan coils remain a very flexible system.

If a client wishes to keep his options open throughout the core build, the fit-out stages and into the future when occupants might change, fan coils can provide that flexibility.

If legislation changes or if refurbishment becomes a requirement, fan coils are likewise best placed to fulfil those needs.

In fact the only two negatives levelled at fan coils, serviceability and noise, have also been greatly improved by the EC fan. This is because EC fans have twice the running life of their AC contemporaries and fan coils employing variable-air-volume strategies (especially self-balancing units that have done away with any volume-control dampers) are far quieter in normal operation.

When EC motors were first discussed there were sceptics, and, if truth be known, those sceptics were mostly manufacturers of fan coils. They claimed that the power factors were all wrong, the harmonics were a problem, no one would pay twice the price etc. — but EC motors have won the day.

2-port PICC valves are the focus of much attention at the moment, but they represent the way forward. As their designs are refined and they become better understood, they will be the future — for a while at least. So are developments such as self-correcting PICC valves, self-commissioning fan coils, fan coils that work autonomously (remote from the BMS) and intelligently in groups all just pipe dreams? Watch this space!

In conclusion we see fan-coil development as a snowball on the top of a mountain. That snowball is rolling now, it cannot be stopped, and its pace is quickening. There will be some false starts and some dead ends, but, at the end of the day, fan coils will adapt to the changing terrain and continue to provide one of the most effective air-conditioning solutions available. Of that there is no doubt!

Peter Lowther is chairman of Ability Projects.

Ability Projects, fan coil units, air conditioning
This version of Ability Projects EC Matrix fan-coil unit can be programmed before being sent to site with information such as air volumes for each duct run and design flow rates for heating and cooling water.
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