Re: [EnergyPlus_Support] Compact HVAC

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

Regarding plenums.  The 5-zone building is modeled with a plenum zone between 
the roof and the ceiling of the occupied zones.  If the return air for the 
system flows through this space without return ducts, then this space is 
designated as a return plenum in the system decription.  This is the way 
CompactHVAC-5ZoneVAVWaterCooled.idf is modeled, but this is not a requirement.  
If the system has return ducts, then the system should be described with no 
return plenum.  This is the way CompactHVAC-5ZoneFurnaceDX.idf is modeled.  In 
conclusion, a return plenum is optional for both of these system types.  I 
would suggest that you try running these examples with and without a return 
plenum to see the impace.  If the plenum is exterior (as in these examples) I 
would expect a signficant change in results.  If the plenum is interior (such 
as between middle floors in a tall building), I would expect the change to be 
small.

Regarding chiller priority, the first chiller will run until the load exceeds 
its capacity, then the second chiller will start while the first chiller 
continues to run.  So, yes, it means two chillers running at the same time, 
when needed.

Mike


On 4 Nov 2005, at 3:59, eric_zhou1223 wrote:

> 
> Hi£¬
> I am studing on the CompactHVAC example files shipped with E+.
> Is a " Return Plenum " an indispensable part in the VAV or Unitary 
> AC equipment model?
> 
> I checked the documentation, it says:
> 
> "Field: Return Plenum Name
> Set to blank if no return plenum is to be modeled. If a return 
> plenum is modeled, it must be
> modeled as a zone with surfaces, and the name of the plenum zone 
> should be entered here."
> 
> So I can conclude that modelling a return plenum may be not 
> essential. Can a VAV system without a return-plenum modelling result 
> in a big difference on the simulation results?
> And in the example file "CompactHVAC-5ZoneFurnaceDX", this field 
> Return Plenum Name is left blank but it does include a return 
> plenum. Is it a carelessness?
> 
> Also,in Compact HVAC:Plant:chiller,for the last cell "priority", it 
> means a sequential start-up operation.
> I just wanna be sure whether it implies two chiller running at same 
> time, instead of an alternative action (when the second shifts in, 
> the first quits )?
> 
> Thank you for your help
> 
> Eric
> 
> 
> 
> 
> 
> 
> 
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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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