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Re: [EnergyPlus_Support] Re: Oversizing in a heating coil



The problem is due to autosizing a system which is providing neutral fresh air 
in a zone where the heating is to be met by baseboard heat.  Both the air 
handler and the baseboard are being sized to meet the entire heating load.  

In this case, the ZONE SIZING heating supply temp is specified as 20C and the 
zone heating setpoint is 20C, so the heating supply air flow rate for the air 
loop is being calculated as 2258.9 m3/s(!) (See component sizing reports in the 
eio output file).

In the ZONE SIZING objects, make these changes, and I think you will get a more 
reasonable result:

    flow/zone,              !- heating design air flow method
    <same value as outside air flow>; !- heating design air flow rate {m3/s}

Mike


On 24 Apr 2006 at 16:34, Elmer Morrissey wrote:

> Hi all,
> 
> I'm sure it is something small, but I cannot spot it. I've uploaded 
> the problem to the files section (in Problem submittals). It's 
> called in 'AA2.idf'. If anyone has the time, I would appreciate the 
> help.
> 
> Kind regards
> 
> -Elmer
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Elmer Morrissey" 
> <elmofuddly@...> wrote:
> >
> > Hello all,
> > 
> > I have a problem with a system. I have three zones which are 
> supplied
> > with fresh air (heated to 20C) and three electric heaters. The
> > electric heaters take priority and as a result, the heated air 
> fresh
> > air picks up any additional heat. The problem is with an autosized
> > system which manages the temperatures in the zones fine, the 
> problem
> > is in the plant loop.
> > 
> > The AHU consists of full FA setup with a supply fan and a heating
> > coil. The heating coil is connected to a constant volume system 
> (with
> > bypass pipes) and a boiler. When I autosize the system, it is set 
> to
> > an overly large level. The heating coil never requires these 
> flowrates
> > so the vast majority of hot water flows through the bypass pipes 
> (less
> > than 1% flows through the heating coil). This means that the pump 
> adds
> > all the heat and the boiler is never required.
> > 
> > Can any point out why the flowrate through the heating coil would 
> be
> > so hugely oversized leading to zero input from a boiler. 
> > 
> > My sizing parameters are 1,4;
> > 
> > Kind regards
> > 
> > -Elmer
> >
> 
> 
> 
> 
> 
> 
> 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@xxxxxxxx





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