Re: [EnergyPlus_Support] Multimode Humidity Control Issues

["Michael J. Witte" <mjwitte@xxxxxxxx>]

1.  If you want the supply air to have a fixed humidity set point, then use Set 
Point Manager:Scheduled with the control variable set to MAXHUMRAT.

2.  The multimode coil in this input has the same performance curves for both 
"Normal Mode" and "Dehumid Mode".  Without different performance for the 
dehumid mode, the coil cannot do anything special.  This option is intended for 
system which switch refrigerant flow, such as sub-cool reheat, to achieve a 
lower SHR in the "dehumid" mode.  If I understand correctly, the DX system you 
are modeling does not operate this way.  I am guessing that it uses cool/reheat 
to achieve the desired supply air humidity.  For that, set the DXSystem:AirLoop 
"Dehumidification Control Type" to CoolReheat.

3.  The multimode coil is not necessary for this, but it won't hurt.  The extra 
input will just be ignored.

4.  I would suggest adding these report variables for the node leaving the DX 
coil to monitor the setpoints and results:

System Node Temp
System Node Setpoint Temp
System Node Humidity Ratio Max
System Node Humidity Ratio

Mike


On 30 Jan 2007 at 20:44, asheaffe wrote:

> I am trying to model a large unitary system with humidity control.  I 
> have taken the previous advice relayed by Richard to use the multimode 
> coil for this purpose.  No matter how I try, I cannot get the humidity 
> control portion of the coil to work.  Furthermore, I am being told 
> that the part-load ratio limits are exceeded.  I am totally stumped 
> here.
> 
> I posted a file D1C_14.zip with the error.  I am trying to create a 
> system which delivers air at a consistent temp of 20C and a wetbulb of 
> 12.5C.  The only way I can see to do this is to create a dummy zone, 
> with no loads that serves as the controlling zone for the humidistat.  
> Is there a better way to do this?
> 
> Thanks,
> 
> Andrew
> 
> 
> 
> 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.
> 
> EnergyPlus Documentation is searchable.  Open EPlusMainMenu.idf and press the "search" button.
>  
> Yahoo! Groups Links
> 
> 
> 
> 
> 


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





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