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[EnergyPlus_Support] Re: humidity control



I am not sure that I would trust the results of a humidistat setting
when running a DX cooling coil system.  The humidistat can probably make
the cooling coil operate, but the part load operation of the DX coil is
currently not calculating a proper SHR correction for part load
operation.  If you were to run a simple model and double the size of a
DX cooling coil, you would see that there is more dehumidification under
part load conditions with the larger unit.  This is counter to observed
field performance of real DX equipment.  Your model probably over
dehumidifies the space with part-load cooling and consequently never
trips the humidistat operation when you most need it. Consequently,
until the DX cooling model is modified, I would not trust either the
calculated interior conditions or the energy consumption of an added
humidistat control used with DX cooling.

Ned Lyon

Senior Staff Engineer
Simpson Gumpertz & Heger Inc.

41 Seyon Street
Building #1, Suite 500
Waltham, MA  02453

Phone:  781-907-9000
Fax:  781-907-9009


>>> shirey@xxxxxxxxxxxxxxxxxx 7/31/2003 8:50:49 AM >>>
Yes the DX cooling coil responds to the humidistat.  Look at the 
documentation for the object UNITARYSYSTEM:BLOWTHRU:HEATCOOL or 
FURNACE:BLOWTHRU:HEATCOOL. Look at the fields related to "high 
humidity control".

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "zhaicq98" <chaoqinz@a...> 
wrote:
> Mike,
> 
> Does the DX cooling coil respond to the humidistat? I compared two 
> files, one with humidistat object, another one without humidistat. 
> But the output of indoor air condition and energy consumption is 
> exactly the same. 
> 
> Thanks,
> Chaoqin
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
> <mjwitte@g...> wrote:
> > Yes, your understanding of the thermostat is correct.
> > 
> > Also, the desiccant dehumidifier does not currently repond to the 
> > humidistat.  It controls to a fixed leaving humidity ratio 
> specified 
> > in the desiccant object.
> > 
> > Mike
> > 
> >


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