By Patrick Burke
It troubles me greatly when I hear well-informed colleagues and influential industry role-players making bold statements.
Some of these bold statements are to the effect of: “VRF will bring about the demise of chillers and chilled water systems,” or, even worse, “VRF is just a split unit on steroids.”
The fact that these respective individuals actually believe this rhetoric not only troubles me, it scares the living bejeebers out of me. At the end of the day, it sends out the wrong message to the end-user or the uninformed.
Yes, I think it’s fair to say that variable refrigerant flow (VRF) has compromised the chiller market to a certain extent, but to imply its imminent downfall is, in my opinion, misguided, not to mention foolhardy.
While in all probability, chiller sales have been impacted negatively, time has an extraordinary way of bringing everything back into perspective. ‘Time will tell’, goes the old adage. How true.
Over time, market forces will once again align themselves – driven by actual experiences in the field – whereby the use of both applications will eventually be dictated to by historical events, rather than merely exuberant sales pitch and hearsay.
Having said all that, the design of a system is entirely dependent on the particular application involved. For instance, no engineer worth his salt would apply a VRF system to serve a pharmaceutical manufacturing process, or for that matter, a deep level mining operation (despite the amount of testosterone prevailing at the time).
By the same token, a chilled water system would not ideally suit a small local convenience-type shopping centre or multi-tenanted office park complex. It is very much a case of ‘horses for courses’, which implies a careful and pragmatic approach to the subject at hand.
Of course there are applications well suited to either option (or even a combination of both). In this instance, a detailed comparison assessment is necessary prior to any decision on the final design choice.
When doing so, the key elements to consider are price, life-cycle cost, plant life expectancy, energy efficiency, environmental footprint, service and maintenance costs, product support and diversity.
In these difficult financial times, price plays a major role in determining the outcome of a project. The end-user wants to pay as little as possible (and of course get the most for his or her buck). This is where the engineer’s skills, integrity and honest endeavours are tested to the full (it’s all too easy to offer a cheaper, less practical option at the expense of a better, well thought out long-term solution).
Energy efficiency is easy to compare given the manufacturer’s published specification and information at hand (such as COP and EER). As it happens, both options will compare favourably in this regard, although, with the chilled water option, this often requires some clever system design input to match the (potential) overall efficiency of a VRF system.
Environmental impact is another easy-to-do comparison, being influenced by operating efficiency, refrigerant choice and heat rejection medium (such as air cooled, adiabatic cooling or evaporative cooling).
Operating and life-cycle costs are vital aspects of any design and equipment selection. Chilled water generators (or chillers) have been around for yonks and as such, the industry is highly experienced in the servicing, repairing and installing this type of plant. The VRF system, being essentially more sophisticated and technically inventive, required a fundamentally more advanced service programme. In essence, the VRF system has more to go wrong due to its revolutionary design.
Sales support is crucial. It is fair to say that this important aspect is unfortunately not generally comparable as it tends to fluctuate from supplier to supplier. A decision in this regard relies entirely on the engineer’s experience and his or her personal relationship with the various suppliers.
All designs take into account diversity (as well they should). In this department, the VRF, if properly designed should win hands-down. Nevertheless, a cleverly designed chilled water plant can run very close, particularly when considering its other redeeming features (lifespan, robustness and reliability).
So, what is the choice? VRF or chilled water? When the time comes, its always going to require a deliberate choice as to the most suitable application.
Personally, I must hasten to admit that in my 50-plus years in the industry, VRF represents, probably the greatest advancement in airconditioning engineering technology to-date.
On the other hand, since its invention in Buffalo, New York, some 118 years ago, chiller development has progressed unabated and continues to advance to meet the world’s most critical challenges. Modern chillers are now incorporating some VRF design concepts to great advantage, particularly with regards to the modular type chiller ranges on offer. You simply can’t sweep this type of commitment under the table.
In summing up, I believe both options provide highly acceptable solutions to most airconditioning applications. Selecting your option of choice is not rocket science. Simply weigh everything up and apply good-old common sense.
One thing’s for sure, both options will be around long into the future, particularly with global warming now a reality.