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Re: [EnergyPlus_Support] about "Purchased air" RH setpoint



My apologies for the late addition here.  

PURCHASED AIR is a very simple system.  Two issues that may present a problem 
for you here:

1.  When using the outside air ventilation rate with PURCHASED AIR, if the zone 
load is small and requires a supply air flow less than the specified outside 
air flow rate, then the OA will be reduced.

2.  PURCHASED AIR supplies air to the zone at a specified humidity ratio.  The 
latent load to provide this is reported as part of Purchased Air Total Cooling 
Energy (or Rate).  Because PURCHASED AIR does not maintain the zone at a 
specified RH setpoint, I believe that summing the "Zone/Sys Moisture Load Rate 
Predicted" will be incorrect.  Whatever latent load is not met in the current 
timestep will appear again as part of the moisture load predicted in the next 
timestep.

Mike




On 28 Jul 2004, at 7:23, Richard Raustad wrote:

> See object ZONE CONTROL:HUMIDISTAT for calculating latent cooling load
> and use the predicted moisture load to view the result:
> 
> Report Variable,
> *, !- Key_Value
> Zone/Sys Moisture Load Rate Predicted, !- Variable_Name
> timestep; !- Reporting_Frequency
> 
> 
> 
> 
> Zheng Li wrote:
> 
> > Dear all:
> >
> > I am using the "Purchased air" to calculate a living/dining room
> > cooling load in summer design day with and without the outside air
> > ventilation rate, i.e., 7.5liter/per person. I want to compare the
> > difference of the sensible and latent cooling load under these two
> > conditions. I have put the indoor temperature setpoint 24C as a
> > "SCHEDULE" and the "ZONE CONTROL: THERMOSTATIC"into the IDF editor,
> > but how can I make a setpoint for indoor RH, i.e., 50% at the same
> > time? Without the RH setpoint, EP also can calculate the cooling load,
> > is there a default RH setpoint in EP? If yes, where and how can I
> > change it value?
> >
> > I am waitting for the answer.
> >
> > Thanks a lot!
> >
> > LI
> >
> >
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> -- 
> Richard A. Raustad
> Senior Research Engineer
> Florida Solar Energy Center
> University of Central Florida
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx




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