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Re: [EnergyPlus_Support] RE:AHU1 Gallery Store PostZTR Hum.idf



If I understand correctly, this system is supposed to supply a fixed flow rate 
at a specified supply temperature rather than adjust supply temperature to 
match the zone load.

Assuming that is correct, the problem is that the various setpoint managers are 
fighting with each other because the cooling coil and heating coil are using 
the same control node.  SET POINT MANAGER:SCHEDULED "AHU1 Supply Air Temp 
Manager" places a setpoint on "AHU1 Fan Outlet Node".  Then SET POINT 
MANAGER:SINGLE ZONE MAX HUM "zBaseGalleryStore Max Hum Manager" places a 
humidity ratio setpoint on the same node.  What is not well-documented is that 
the CONTROLLER:SIMPLE resets the control node setpoint if the max humidity 
conditions requires more cooling.  To see the impact of this, add report 
variable "System Node Setpoint Temp" for AHU1 FAN OUTLET NODE.

Because of this, the heating coil controller needs to use a different control 
node.  An easy solution would be to add "AHU1 HC Outlet Node" to the NODE LIST 
for "Supply Air Temp Nodes".  And change the AHU1 Heating Coil Controller 
control node to be "AHU1 HC Outlet Node".  This should solve the problem.

Mike


On 12 Sep 2005, at 14:58, civilnug wrote:

> Hi All,
> 
> I've put the above idf in the Problem_Submittals file. In it I have, 
> in order, a mixing box, cooling coil, heating coil and humidifier on 
> the air loop. This is fed into an area by a direct air system and has 
> to have tightly controlled relative humidity levels (50% +/- 5%). The 
> system is operating perfectly in winter but my problem is occuring 
> during the summer months when attempting to get control of the rh. 
> 
> The cooling coil kicks in to drag down the temperature below the 
> supply air temperature so as to get the humidity ratio to the right 
> level, my problem is that the heating coil won't kick in to bring the 
> temperature back up to the specified supply air temperature.
> 
> Any help would be greatly appreciated.
> 
> Regards,
> John McCarthy.
> 
> 
> 
> 
> 
> 
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
> 
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
> 
> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 
> 
> 



========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx




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