Engineered Systems - January 2009 - (Page 11) Letters McKew responds: Thanks for the feedback. I’ll pass it on to the TC committee and continue my own education on HVAC Security. author, there are no controls on the primary air supply at the chilled beams, so the system delivers conditioned 100% outdoor air to all units, whether needed or not. In spaces with little or no cooling load, the space can be overcooled unless reheat is used, and depending on the quantity of primary air. There is no information about the extent to which the design meets the local energy and ventilation codes for both the perimeter and interior systems. Continuously tempering and reheating 100% outdoor air from 50°F to 58° for humidity control imposes both additional heating and cooling loads and increases energy consumption during all occupied hours, since the additional heat must also be removed somehow. With only two AHUs serving this system, it is also necessary to supply conditioned air to at least half of the building, even when only a single person requires after hours comfort. Even if heat recovery was used, which was not mentioned in the article, this could be a large energy waste. Since only a portion of the cooling is supplied by the air system, it is not possible to have full economy cycle capability, which can result in energy penalties for office buildings in some climates and depending on the cooling loads. Thus, chilled water must be produced and consumed for more hours than otherwise, increasing energy use. Another problem is that the design shown in the figures and photo in the article is clearly a two-pipe system, so it is not possible to have simultaneous heating and cooling when needed. The author also does Chilled beam criticism The article titled “Chilled Beams in Chicago” by Thomas Posko, P.E. in the October 2008 Engineered Systems (page 42) claims to describe the first application of what he calls chilled beams in this country. What the author calls chilled beams, are more commonly known as induction beams, active chilled beams, or ventilated chilled beams, and have long been known as ceiling-mounted induction units. Contrary to the claim by the author, ceiling mounted induction units were available and used long ago. For one example, see “Solar Energy and Large Building HVAC Systems: Are They Compatible?” by Milton Meckler in the ASHRAE Journal, Vol. 19, No. 11, 1977. On page 26 in the 1970 ASHRAE Guide and Data Book, it states, “Induction … units designed for overhead installation are available.” While some chilled beams are often described as passive systems, they are often known as convective or radiant ceiling panels. Radiant cooling and heating ceilings have been used in this country for at least 40 years. In the Philadelphia area, I can recall large buildings from the 1960s with radiant ceilings such as the Bell Telephone Headquarters, Foxcroft Pavilion, and Moore Products Company. In the way the chilled beam system is described and shown by the Mainstream… co onditioning critical envir ronments se Easy-to-us selection software Exact mat tch replacements Emergenc 1-day shipment cy No-thru-metal, total thermal break Certified air leakage rates as low as 0.5% at 15” w.g. Foam-injected insulation up to R-26 Long lasting powder-coat finish Input 224 at www.esmagazine.com/instantproductinfo Cranford, NJ | (908) 931-1010 www.cu ustomahu.com ESM01094Main.indd 1 12/23/08 w w w. esmag a zine . c o m 3:06:31 PM 11 http://www.customahu.com http://www.esmagazine.com/instantproductinfo http://www.esmagazine.com
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