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[EnergyPlus_Support] PROBLEMS WITH THE REGULATION

PROBLEMS WITH THE REGULATION

Dear All,

I'm modeling an HVAC system composed by an Air Handling Unit with sections of pre-heating, cooling, and post-heating as you can see in the attached outline (the umidification section is actually missing in the model). The ADU serves two zones of about same dimensions and thermal chatacteristics. The post-heating coils is controlled by a scheduled set-point manager that detects the temperature in the node called a13, that is the common retourn of the two zone. Pre-heating coil (modeleld as an electric one, and the post-heating too) in winter period, and cooling coil (modeled as a water one) in summer period works at fixed point by set-point manager scheduled; their control nodes are just downstream the component themselves. Their regulation is PERFECT.
Instead the post-heating coil bheaviour is unstable, with fluctuations as larger as outdoor air temperature is far from that of set-point, then in winter I have the worst situation (see the graphs --- The fluctuations of the supply air temperature are even greater. It is supposed a 24/7 operation time). Note that the working starting point for the post-heating coil is always a constant temperaure, wich is achieved by the pre-heating or cooling coil respectively, so that outdoor air temperature should not have influences any more on post-heating coil operation.
All that is in total absence of internal gains and infiltrations and with low solar gains.
So, wich is the regulation applied by EnergyPlus in the simulation?
I'm guessig  EnergyPlus applies a regulations that HOWEVER takes into account the outdoor temperature trend. 
Someone can give me some suggestions?
However I'm interested to enhance my knowledge about the regulation implemented in energyplus (PI, PID?), and at the moment I did not find in the documentation the answers I'm looking for.
Thanks to all
If interested, I can post the IDF file in the same folder 

link to graphs:

https://www.dropbox.com/sh/m9g1aw2ylji5c99/1AB9RCwBTt


Best regards

Alessandro

Ing. Alessandro Gober
assegnista di ricerca
CIRI-EC - Facoltà di Ingegneria - Università di Bologna
Via Terracini, 28 ? 40131 Bologna ? Italia
http://www.edilizia-costruzioni.unibo.it

alessandro.gober@xxxxxxxx
tel: +39 051 2090566




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