Re: [EnergyPlus_Support] unable to reach set point temperatures in zones

["Jean Marais jeannieboef@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>]

Hi, the lag I refer to is the amount of additional time it takes to transfer the thermal energy to the air. Think of it as a response time. When I turn the fancoil on 100% it will condition the air very quickly, whereas the radiant system is still getting to the needed temperature. This is more true the more massive the structure. E+ has now also a simplified radiant model (previously only the massively imbedded pipe model was available) which may be more responsive and possibly better simulates the more lightweight hanged hydronic ceiling panels.

Generally, for this reason, avoid changing the setpoint temperature by more than 2 Kelvin or turning the equipment on and off too often (there are exceptions, but this is a good starting point).

Re sizing: Chilled ceiling...77 W/m2 is pretty exact, but in the right ball park for a chilled ceiling. Rating values relevant only for the active area are about 65 to 125 W/m2 depending on rating conditions and technology. 

Re Setpoint Schedule: I use compact schedules exclusively. Therein I define the air setpoint that the equipment will try to meet at any given time on any day type. If you need to, define other values for the day type summerdesignday and winterdesignday. I suggest always keeping the same value here to avoid steps resulting in peak loads and oversized equipment.

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Posted by: Jean Marais <jeannieboef@xxxxxxxxx>

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