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Juan Francisco, This is a very good question to which there are as many valid responses as there are responders. My feeling is that traditional methods for sizing cooling equipment lead to very over sized equipment and the energy inefficiency that comes with it. Traditional sizing involves a steady-state, worst-case scenario when all the equipment is on, all the lights are on, and all the people are in the building. Some tools also do not account for zone adjacencies; they compute the worst case assuming that all zones are thermally isolated from each other. There is no credit for thermal mass and no credit for shading. That is obviously going to give you the greatest possible cooling load. There are lots and lots of other justifiable methods, some of which you mention. What I have done in the past is to look at what the peak cooling load is under a number of these methods (with normal building operation during an average weather year, including shading, excluding shading, during an "extreme" weather sequence of days, during a "design day" that repeats itself. From multiple tests, you can get an idea of how sensitive the peak cooling load is. You can then do some experiments of limiting the available cooling power in order to see how badly you miss your target cooling temperature. If the overshoot is small, then under sizing the equipment a little bit will create energy savings and the comfort penalty will not be great. With all that information, it is then possible to do an informed sizing the cooling equipment. Best, David On 10/3/2012 04:44, JUAN FRANCISCO
BELMONTE TOLEDO wrote:
-- *************************** David BRADLEY Principal Thermal Energy Systems Specialists, LLC 22 North Carroll Street - suite 370 Madison, WI 53703 USA P:+1.608.274.2577 F:+1.608.278.1475 d.bradley@tess-inc.com http://www.tess-inc.com http://www.trnsys.com |