[EnergyPlus_Support] Design Cooling and Heating Loads

["joao.rosa83" <joao.rosa83@xxxxxxxxx>]

Hello,

I want to simulate an AHU system for several zones, so i need to obtain the design heating and cooling loads. I'm a new user so first i want to obtain the loads with the ideal loads system and then compare to the loads obtained by the sizing:system and sizing:zone.

The AHU system works with 100 % outside air, without mixing between the supply air and the air returning from the zones.

First question: It is possible to simulate a system with 100% outside air without mixing with the exhaust air zone? In the ideal loads the outside air is mixed with zone exhaust air and then heated or cooled in order to matach the zone demand given by the thermostat. If the air is pre-mixed there are less loads compared to the case where the system has to cool/heat the outside air. 

Second Question: When i simulate the AHU system for the several zones (with the airloops, cooling/heating coils,.....) what represents the zone design load? When I size the zone I need to put the zone air supply conditions (temperature and humidity) and then the program calculates the design air flow to the zone. In the sizing:system the program uses the sum of all the zones air flow and then sizes the heating and cooling coils for the conditions that I want to supply the air (the conditions that I put to the zone air supply). I don't understand why the sum of all the zone heating/cooling loads it is not equal to the heating/cooling sizing of my AHU system.

Sorry for my bad English. Thanks for your help. 

João



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