From the industry
APPLICATION : VRF OR CHILLED WATER – IT ' S YOUR BOTTOM ON THE LINE
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 . RACA
www . hvacronline . co . za RACA Journal I April 2021 41