Thibaut, You are correct; the assumption that underlies the lumped capacitance approach is that the entire building (envelope and air) is at a single temperature. Moving the setpoint requires the HVAC system to move the temperature of the air and the structure. I have seen three workarounds to this issue. One is to simply limit the heating and cooling capacity of the system so that the air and structure warm up at a realisitc rate. You need to use the "temperature level control" version of Type660 and you need to find the peak iteratively instead of letting the model calculate it for you. The second is to model the building as two lumped capacitances, one for the air and the other for the shell (Type953 is available in the TESS Loads and Structures library). Unfortunately, this gets farther away from allowing you to set any "physical" values; for instance it is hard to know how to appropriately couple the two capacitances. The third is to artificially reduce the capacitance of the building so that most of what you are accounting for is the air (with a little bit for the structure and furnishings). Best, David On 3/29/2012 09:29, Thibaut VITTE wrote: Dear Trnsys users, -- *************************** 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 |