[EnergyPlus_Support] Re: Oversized equipment

["eric_zhou1223" <eric_zhou1223@xxxxxxxxx>]

Thank you for the response,Mike. It sounds like my description of 
OAFractionSched misled you. In fact, I have to get preliminary sizes 
when I start to simulate a A/C system. The real air conditoning unit 
is however an oversized one than the E+ suggest --it can supply 
overmuch cooling amount than needs. Users have to adjuge the FA 
damper to force normal outdoor air intake.  In this simulation, I 
use the real FA flow rate (about same with the autosize value) , and 
the real cooling capactiy(larger than the autosize value).  
The "flowrate/capacity" will be out of range.  How can I simulate 
this case?

Or I can describe it like this:  I simulate an AC unit and get good 
autosize values about the unit. Then given that I want to know what 
it will look like to change to an oversized equipment, by keep 
preliminary size of OA and enlarge the nominal cooling supply two 
times --this situation I guess could happen in reality.
I hope this time I explain the question clearer. THank you in 
advance.


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
<mjwitte@...> wrote:
>
> My apologies for the delayed response.
> 
> I am not sure I understand completely what you are trying to do.  
When 
> economizer operation is not active, the outside air flow rate is 
calculated as 
> follows.  All names in quotes are field names for 
CONTROLLER:OUTSIDE AIR:
> 
> a) If "MinimumLimit"=FIXED MINIMUM, then OAFlowRate = "minimum 
outside air flow 
> rate" * "Minimum Outside Air Schedule"
> 
> b) If "MinimumLimit"=PROPORTIONAL MINIMUM, then OAFlowRate 
= "minimum outside 
> air flow rate" * "Minimum Outside Air Schedule" * (Current system 
flow 
> rate/Design system flow rate) 
> 
> It sound like you need to specify a value for "minimum outside air 
flow rate".  
> If you autosize this, the autosize value is the sum of the outside 
air 
> requirements in the ZONE SIZING objects for zones served by this 
air loop.
> 
> Does this give you enough information to control the outside air 
flow as 
> desired?
> 
> On 7 May 2006 at 4:12, eric_zhou1223 wrote:
> 
> >   Hi all,
> > 
> >  I was trying to simulate  an oversized equipment in a real 
> > project.  A huge amount of outside air was introduced in the 
> > simulation, because I must manually size both the capacity and 
flow 
> > rate at the same time and increase them proportionally to avoid 
the 
> > out of range error.
> > 
> > To keep appropriate outdoor air intake,  I have to remain the 
> > autosizing value of airflow rate while only to increase the 
> > autosized capacity to the real value by some way.
> > 
> > I noticed there is a OAFractionSched in Controller:outside Air 
which 
> > now is all set to 1. Can I change it to a small number (such as 
> > 0.01) to consider a situation where an oversized equipment is 
used 
> > like in my case?   Is it the key to solve an oversized unit's 
> > simulation?  I found modifying OAFractionSched as 0.01 didnot 
lead 
> > to an expected result like "OA =0.01* original air flowrate" . 
> > Instead,it was a much smaller value seemingly no related to the 
> > original one.
> >  
> > Could anybody instruct me how to simulate an oversized equipment 
> > like this? Thank you.
> > 
> > Eric
> > 
> > 
> > 
> > 
> > 
> > 
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> > 
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> > 
> > Attachments are not allowed -- please post any files to the 
appropriate folder
> > in the Files area of the Support Web Site.
> > 
> > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.idf 
and press the
> > "search" button.
> >  
> > Yahoo! Groups Links
> > 
> > 
> > 
> >  
> > 
> > 
> > 
> > 
> 
> 
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support      
> EnergyPlus-Support@...
>







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