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Damien, In my experience, there are relatively few heat pumps available on the market that can do what you are trying to do. Most heat pumps have a fairly fixed capacity (some have multiple stages) so that they have an easier time maintaining a fixed temperature rise than they do in maintaining a fixed temperature outlet. There is at least one notable exception to this; an air-to-water heat pump that has a variable speed compressor that allows it to modulate and maintain a target outlet temperature. Type927 is a temperature level control device meaning that it is looking for inlet water conditions on both sides and for a control signal. If you have obtained your heating loads from some other software tool, I would recommend that you read them into TRNSYS using Type9 and impose them on a water stream using Type682 from the TESS Loads and Structures library. I would then place a thermostat sensing water return temperature in the loop and I would use its output to turn on the loop pump and the Type927 heat pump. You will not get a constant supply temperature of course but in reality, a single stage (or even multi stage) heat pump can't really give you a constant supply temperature; it can only give you a supply temperature that hovers around a set point. If you are using Type56 to generate your building's heating demand, I would take it out of energy rate control (ie turn OFF the automatic heating and cooling types in TRNBuild), and allow the zone temperatures to float. I would then use a thermostat watching the zone air temperature and some kind of delivery device (a fan coil, radiant floors, etc.) to deliver the hot water from the Type927 to the zone. Kind regards, david On 6/6/2012 12:20, Damien Casetta wrote: Hi, -- *************************** 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 |