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Why term as arbitrary?

Dan Mizesko keeps the VRF versus CHW systems debate alive, asks for evidence to bolster claims made by VRF manufacturers and an MEP contractor

| | Oct 13, 2021 | 12:18 pm
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I read the September 2021 issue of Climate Control Middle East, which carried responses (titled ‘Arbitrary conclusions’) to my earlier article in the July 2021 issue, titled ‘Don’t believe the hype about VRF systems’.

I was eagerly awaiting the responses, as I enjoy a good debate; however, this should not be much of a debate. I must say I was very clear in the article when I stated that I decided to investigate and research the VRF industry’s claims of superior efficiency versus chilled water systems; and thus, most of the information I was presenting was taken from industry literature and studies conducted by recognised industry professionals and organisations; they were not so much my observations.

As for the responses, I could find no studies or data to support statements made by the VRF manufacturers regarding their claims of superior efficiency. It was clear to me that the authors – Utpal Joshi, of Daikin; V. Sekhar Reddy, of Lexzander; and Dharmesh Sawant, of Hisense – who responded individually, did not understand this, as they offered no study on the superior efficiency of VRF systems.

Manufacturers of VRF systems claim that the lifecycle cost of VRF technology is lower than that of chilled water-based systems, stating that VRF systems waste less energy, have higher rated efficiency and require simpler, more streamlined maintenance. These industry claims are not supported by studies. ASHRAE decided to test both systems in its Atlanta headquarters and to meter and measure their performance. Again, the main purpose of my article was to inform the reader that VRF systems are not more efficient than chilled water systems.

Dan Mizesko

The ASHRAE study of a VRF system and a chilled water system, installed in the same building and addressing similar loads, revealed that on an annualised basis, the VRF system had an energy consumption that was 57% higher in 2010 than the hydronic system, 84% higher in 2011 and 61% higher in 2012.

The above was an ASHRAE study. My statements on efficiency or non-efficiency of VRF systems versus chilled water systems were based on an ASHRAE study. So, I guess the authors on the other side of the debate find ASHRAE’s study an “arbitrary conclusion, questionable, inaccurate and exaggerated”.

It’s difficult to respond to the three gentlemen who have conveniently not even mentioned the independent ASHRAE study, which conclusively proved chilled water systems as being more efficient than VRF systems.

Efficiency was the main purpose of my article. Why did the three gentlemen not even address that in a head-to-head ASHRAE study of the two technologies, the chilled water hydronic system was more efficient than the VRF system by as high as 84%? Why did the gentlemen not provide a counter study? I will tell you why, because as I stated in my July 2021 article, I could find no studies or data to support statements made by VRF manufacturers and proponents regarding their claims of superior efficiency.

I have, however, found another study, which again questions the claims of the VRF industry. The concern over sparse data has been noted in a number of papers on VRF, including a report prepared by the Pacific Northwest National Laboratory for the U.S. General Services Administration. The report states, “Surprisingly, despite the long history with VRF technology in Europe, Japan and elsewhere, the U.S. research community has not found useful research on VRF from these places. While some general literature is available about these systems, there is a lack of critical evaluation of actual field energy performance.”

I also cite another research project, involving a lab test, which provided performance information under different conditions for both VRF heat pumps and heat‐recovery systems for incorporation into building simulation models. The lab test, performed by Florida Solar Energy Center and EPRI, was funded by Bonneville Power Administration, Southern California Edison and U.S. DOE.

It raised questions about possible differences between actual VRF performance and the AHRI‐certified performance. The EPRI lab test incorporated a different approach and a different purpose than the AHRI test. In the AHRI test, some variable settings are fixed by the manufacturer, while the EPRI lab test allowed the system settings to vary, similar to how they perform in buildings.

It is apparent with the ASHRAE study and the above research that VRF systems operate less efficiently in the real-world versus what is stated on paper and, without question, do not perform to the efficiency of a chilled water system. In addition to strong mixed views on efficiency, a number of perceptions exist among industry professionals on the advantages and disadvantages of VRF systems, driven in large part by aggressive marketing campaigns by VRF manufacturers. Other factors that can significantly impact the bottom line must also be taken into account.

Lifecycle costs VRF systems generally have a shorter life expectancy than hydronic systems. Hydronic systems have been known to last 25 years, Dan Mizesko keeps the VRF versus CHW systems debate alive, asks for evidence to bolster claims made by VRF manufacturers and an MEP contractor while VRF systems could need replacing as early as 15 years after installation.

The initial cost of a hydronic system is generally lower, and systems offer a much wider range of flexibility for components, operation and maintenance, in terms of parts and service. Advanced systems include application of technologies, such as pumps equipped with variable-speed drives and Chiller Plant Energy Optimisation programmes that further increase energy efficiency. Components in a chilled water system are factory-made and factory-tested, reducing rate of failure after installation. Since VRF piping requires brazing and soldering on-site, the quality of the installation depends on the level of expertise of the installer.

Installers also must be qualified to work with refrigerants under extremely high pressure and be knowledgeable about leak detection and ventilation requirements, as per ASHRAE Standard 15. In the GCC region, the weather matters. High temperatures can impact system performance of chilled water and VRF systems; however, chilled water systems are less affected by temperature changes.

For VRF systems, efficiency is reduced, if the ambient temperature goes up. Another big selling point of a VRF system is that it can provide simultaneous heating and cooling, and can recover heat from one zone and use it in another. Is this even a consideration in the Gulf? This is a selling feature in buildings located in cooler climates, not in the UAE and Qatar. I will now address a few points made in response to my article by the three authors that I found to be disingenuous and slanted to try and make VRF systems seem superior to chilled water-based systems.

1. Compressors on chilled water plants are old twin screw technology and the compressors cannot be field-repaired. This statement is incorrect. Compressors on chilled water plants are not all old screw technology; in fact, most are centrifugal compressor technology, which is the most efficient compressor in the HVAC industry. Additionally, field service and complete overhaul of a twin-screw compressor can, and are performed, in the field. The centrifugal compressor, by the way, is also field-serviced and field-repaired. Why did the authors fail to mention that VRF compressors are actually not field-serviceable? They have to be replaced when they fail. Why was this information withheld?

2. If there is a problem with a chilled water system, the owner has to identify the fault, a formidable task. Any qualified chiller specialist organisation can easily identify the equipment fault – be it involving the chiller, pumps, towers or control system – and make corrective repairs without the owner being involved in identifying the problem.

3. The need for condensate drain lines for each VRF indoor unit. CHW fan-coil units need condensate drain lines, so I don’t see the issue. This statement was answered by one of the three writers for me, who wrote, it was stated that all air systems comprising AHU and VAV do not comprise a practical solution for every application. In fact, the sheer variety of VRF FCUs is common knowledge. So, the problem is the vast number of FCUs, which will be much higher with a VRF system versus a chilled water system’s requirement. Thus the need for more condensate drains in a VRF system. In my view, that is the issue.

4. Compliance with maximum allowable refrigerant requirements within a given volume. In relative terms, it doesn’t matter, as both are closed systems. Again, the writer in question does not understand the issue. With a chiller, the refrigerant volume is not in an occupied space, exposing building occupants. It is in the chiller plant room, and if a leak does occur, it is contained in a space with no building occupants. Refrigerant alarms and crash fans are also installed in the plant room as per ASHRAE 15 standard, so there is no health risk to building occupants. This is not the case with a VRF system. That is the issue.

5. For claims relating to energy efficiency, data is available in abundance – I’m happy to point to many buildings with Daikin cloud, providing live and continuous energy data on dashboards. Providing live data from your energy dashboards is not a study of VRF efficiency versus chilled water-based systems. I can also provide you with data that chillers are more efficient. Actual studies are the only way to draw a real conclusion, and an ASHRAE study would be most valuable… but we already have that, don’t we?

6. The statement was made that VRF will not exceed 1.4 kW per ton. This statement makes the case for superior chilled water systems efficiency. We operate, maintain and service many chilled water plants – standalone as well as district cooling plants – that are running in the range starting from 0.7 to 0.9 kW per ton. This includes chillers, CW and CHW pump and tower fan loads, which all combined are operating well below the 1.4 kW per ton highlighted. In addition, there are air-cooled chillers, now available, that also operate well below the 1.4 kW per ton. The writer in question proved my point that chilled water systems are more efficient than VRF systems.

I am going to conclude this response, as I could counter each and every point made to my article – including the facts that VRF systems operate under extremely high pressure, another issue that can lead to leaks, the long runs of refrigerant piping causing published efficiencies to be incorrect, the high global warming issues with R410A, along with many other issues – but I do not want to waste the reader’s time. My issues and concerns are documented in my article in the July 2021 issue.

My article was written to educate the readers to not be misled by false statements that VRF systems are more efficient than chilled water systems, because they are not, and that is a proven fact.

Nothing in the response article, stated by any of the three gentlemen, changes this fact or even comes close to challenging this fact. I urge them to once again take a look at ASHRAE’s independent study and its determination that VRF systems are not as efficient as chilled water systems, and the case is closed. That was actually the thrust of my July 2021 article. Chilled water systems are the most efficient systems, and VRF systems are not. Full stop.

Dan Mizesko is Managing Partner/President, U.S. Chiller Services International. He may be contacted at dmizesko@uscsny.com

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