Letter from Thomas R. Edwards, Ruskin Group, Grandview, Mo.:
I just completed reading your two-part article on DOAS and VRF (“Combining DOAS and VRF, Part 1 of 2,” March 2014, http://bit.ly/Bowers_0314, and “Combining DOAS and VRF, Part 2 of 2” April 2014). Of course, VRF certainly makes sense in a variety of applications—most specifically, where ductwork is not available or jobs where it is not practical to install. However, the author is assuming benefits vs. ducted VAV systems, and in my experience, it doesn’t add up in both first cost and life-cycle costs in North America climates for the following reasons:
• These systems have been sold in the U.S. since 1983. The reason they have not had a lot of success is because they not only cost more, but typically are not more efficient than ducted VAV systems.
• VAV systems sometimes get a bum rap by not including…
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