Re: [EnergyPlus_Support] Hotel Model PTAC Sizing

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

The SYSTEM SIZING object is interacting with the ZONE SIZING.  When a user-
specified supply air flow rate is present in the SYSTEM SIZING object, the 
sizing algorithm assumes the users wants to scale all of the zone supply air 
flow rates to match the specified value.  This is altering the PTAC autosized 
flow rates.  The following change will fix this:

Exisiting SYSTEM SIZING object contains:

    flow/system,             !- cooling design air flow method
    3.1152,                  !- cooling design air flow rate {m3/s}
    flow/system,             !- heating design air flow method
    3.1152;                  !- heating design air flow rate {m3/s}

Change these lines to:

    design day,             !- cooling design air flow method
    ,                  !- cooling design air flow rate {m3/s}
    design day,             !- heating design air flow method
    ;                  !- heating design air flow rate {m3/s}

This will eliminate the interaction of the system sizing object and the zone 
sizing.  This requires that the DOAS be fully hard-sized (or nearly so).  In 
this input file, that is the case.

Mike


On 9 Mar 2007 at 22:04, asheaffe wrote:

> I have been trying to get a DOAS model working with PTACs.  The model 
> is posted as D1C_397.  It uses a central system to deliver ventilation 
> air at a constant 20C and PTACs to heat or cool from there to 
> thermostat setpoints.  The problem I am having is that the PTAC sizing 
> is inaccurate and doesn't respond to changes in the zone sizing 
> object.  I had talked to Mike Witte before about this model and we 
> agreed that this method should work.  Any Ideas?
> 
> Thanks,
> 
> Andrew
> 
> 
> 
> 
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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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