Re: [EnergyPlus_Support] Re: humidity control

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

1.  The zone supply air flow rates are calculated by ZONE SIZING based on 
sensible load requirements, so the SYSTEM SIZING object will not alter the air 
flow rates.  Also, note that the "type of load to size on" field in the SYSTEM 
SIZING object only accepts "sensible" (see Input Output Reference).  I see that 
the IDD file does not mention this, so I will add a note.

2. In the file you submitted last week, in CONTROLLER:OUTSIDE AIR, ECONOMIZER 
is active.  If that is active in your current idf, then that would explain the 
increase in outside air flow.

3. Check the setpoint controls on the main heating coil.  It should attempt to 
heat the air to the desired setpoint, assuming that the entering hot water 
temperature is adequate.

Mike


On 6 Jun 2006 at 9:26, hbn_pch wrote:

> Mike,i report the system node temp and system node volflowrate,find 
> that system node temp is low enough(perhaps had achieved dew point) 
> but system node volflowrate remain max(sizing in eio).It seems that 
> the air loop capability is sized too small.Then i adjust the sizing 
> parameter to 2 and find it can control temp and hum well.I try 
> another model for a test,find it should set sizing parameter to 3 for 
> control aim.All is autosized in the model.Why is it sized so small?
> Does it just sized the sensible load?But when i change the size type 
> in system sizing to total,the result did not change yet.
> 
> question 2 :I set 0.0094m3/s in the zone sizing for outside air and 
> oa method is flow/person.There is 20 people in the zone,min oa remain 
> 1.So for all day,the outside air volflowrate should remain 
> 0.188m3/s.But for simulation ,i find sometimes the outside air 
> volflowrate would increase.What caused this change?
> 
> question 3 :When i use vav:reheat,i set the vav outlet node temp in 
> winter to 16.I find in winter design day,the vav damper remain min 
> and the vav outlet node temp did not achieve setpoint temp.I checked 
> other simulation day,find that the vav outlet node temp did't not 
> achieved setpoint at all,sometimes are very small.Then it will be 
> reheated by reheat coil .How did the main heating coil and reheat 
> coil distribue the heating task?
> 
>   Appreciated your kind help.
>   PCH
> 
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "mjwitte" <mjwitte@...> 
> wrote:
> >
> > If you report the System Node Setpoint Temp at the air loop outlet
> > node, you will see that the controller is trying to control to the
> > specified RH setpoint, but the cooling coil is unable to supply air
> > that is cold enough to meet this.  I tried making some changes to 
> get
> > this to autosize to a better result, but have not been successful 
> yet.
> > 
> > Mike
> > 
> > 
> > 
> > 
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "hbn_pch" <hbn_pch@> 
> wrote:
> > >
> > > Dear,
> > >    I want to control humidity for a single zone.I create the 
> model like 
> > > the examplefile '5ZoneWaterCooled_HighRHControl.idf',but the Zone 
> Air 
> > > Relative Humidit was not controlled to setpoint in my model,while 
> the 
> > > examplefile can.
> > >    I really can't find the problems.appreciated your kind 
> help.I've 
> > > upload  correlative file named 'RH CONTROL.zip'
> > >    Thanks very much
> > >    pch
> > >
> >
> 
> 
> 
> 
> 
> 
> 
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> 
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>  
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> 
> 
> 
>  
> 
> 
> 
> 
> 


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





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