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Re: [EnergyPlus_Support] Zone heating loads and heating meter not equal

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Zone heating loads and heating meter not equal
From: "Michael J. Witte" <mjwitte@xxxxxxxx>
Date: Fri, 26 May 2006 13:01:33 -0500
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> 3b.  The parasitic electric power is also adjusted by PLR (intended to
> model load-dependent parasitics such as a draft inducer fan), but it
> appears there is an error here.  Even when the boiler load is zero, the
> MinPLR times the parasitic load is being consumed.  Only 7.5W in this
> case, but it shows up every hour.  A bug report will be posted for
> this. 

A clarification on this.  This file is for version 1.2.3.  When transitioned to 
1.3.0, the occurence of parasitic loads with zero boiler load are greatly 
reduced.  I also checked several example files with boilers and did not find 
this problem occuring (every time the boiler load was zero, the parasitic load 
was also zero).  So, this problem is not as global as I thought.

Mike
  


On 26 May 2006 at 10:07, Michael J. Witte wrote:

> 1.  First, why is Heating:Electricity not equal to Boiler Electric
> Consumption? 
>  Searching the .mtd output file for Heating:Electricity shows that Boiler 
> Parasitic Electric Consumption is also on that meter and reported by the
> boiler 
> as a separate value (not included in Boiler Electric Consumption).  
> 
> 2.  Second, the boiler theoretical efficiency is 0.8.  I presume you intended
> something closer to 1.0.  The BOILER:SIMPLE model does not explicitly compute
> losses from the boiler to its surroundings, so this probably should be
> slightly 
> less than 1.0 for an electric boiler.  
> 
> 3.  Third, the boiler "Minimum Part Load Ratio" (MinPLR) is set to 0.1.  
> 
> 3a.  When the boiler has a load greater than zero, but less than 0.1, the 
> boiler will consume 0.1 of full-load power.  
> 
> 3b.  The parasitic electric power is also adjusted by PLR (intended to model
> load-dependent parasitics such as a draft inducer fan), but it appears there
> is 
> an error here.  Even when the boiler load is zero, the MinPLR times the 
> parasitic load is being consumed.  Only 7.5W in this case, but it shows up 
> every hour.  A bug report will be posted for this.  
> 
> 3c.  There are max iteration errors occuring, and there is an open CR related
> to equipment MinPLRs and iteration problems.  In this case (variableflow
> boiler 
> with varible speed pump and non-zero MinPLR) the problem is showing up.  
> Setting the MinPLR to zero eliminates the max iteration errors (reducing 
> execution time significantly).  
> 
> 4.  There was a bug in version 1.2.3 (CR 6877) with variable flow plant loops
> where temperatures did not always resolve completely.  This is fixed in
> version 
> 1.3.0.  This has a minor impact, but can contribute to some differences.  
> 
> So, with pump heat at zero, MinPLR at zero, and Efficiency at 1.0 (using 
> version 1.2.3), the coil load and boiler output agree within 0.1%, and the
> main 
> boiler electric consumption equals the boiler output.  
> 
> Mike
> 
> 
> On 26 May 2006 at 17:31, Sam Roose wrote:
> 
> > Setting the pump head to zero gives me 1.25 (instead of 1.06) and 0.52
> > (instead of 0.47).
> > I can see what you mean by the chiller COP varying now. The chiller output
> > meets the chiller electricity * the chiller COP now.
> > The boiler output is still some way form meeting the boiler electricity,
> and
> > does not balance after a long time.
> > 
> > So...
> > 
> > Chiller Electric Power is virtually equal to cooling electricty
> > Chiller electric power x COP is virtually equal to both (total zone
> cooling
> > coil use + chilled water pump electricity) and chiller evap heat trans
> rate.
> > 
> > However, Boiler electric power and Heating electricity are not quite equal
> > and Boiler electric power is not close to equalling (total zone cooling +
> > hot water pump electricity). Any ideas?
> > 
> > Sam
> > 
> >  5/26/06 5:10 AM, "Michael J. Witte" <mjwitte@xxxxxxxx> wrote:
> > 
> > > Are you allowing for pump heat in the hot/chilled water loops?  Try
> > setting
> > > the 
> > > pump head to zero to eliminate pump heat, then check again.  Also, the
> > chiller
> > > efficiency is probably not constant (unless you are using the constant
> COP
> > > chiller).  First, check that the chiller evap heat transfer load matches
> > the
> > > coil loads (plus pump heat).  Then look at the chiller COPs to  see if
> the
> > > electric consumption is reasonable.  Also, if the chilled/hot water loop
> > > temperatures are not maintaining setpoint at all times, there will be an
> > > imbalance until the loop returns to setpoint, but the energy should
> > balance
> > > when summed over time.
> > > 
> > > Mike
> > > 
> > > 
> > > On 25 May 2006 at 18:05, Sam Roose wrote:
> > > 
> > >> > I have just uploaded a file called "DESIGN_DAY_WEATHERFILE" that
> works
> > >> fine,
> > >> > except that the sum of the zone heating loads in the output file
> (total
> > >> > water heating coil energy for 25 zones) does not equal the "Heating:
> > >> > Electricity" meter, which is the same value as the boiler electricity
> > once
> > >> > converted to kWh. The same occurs with cooling (sum of total water
> > cooling
> > >> > coil rate vs cooling:electricity). With the file I have sent, the sum
> of
> > >>
> > the
> > >> > heating coils is 1.06 of the heating meter (should be 1.00) and the
> sum
> > of
> > >> > the cooling coils is 0.47 (should be 0.33 due to a COP of 3 being
> > used).
> > >> > 
> > >> > I have noticed I can bring the zone heating load sum more into line
> with
> > >>
> > the
> > >> > heating meter by changing the maximum and minimum supply temperatures
> in
> > >>
> > the
> > >> > autosizing inputs, but the values diverge again if I make a major
> > design
> > >> > change.
> > >> > 
> > >> > The file was set up in version 1.2.3
> > >> > 
> > >> > Is the sum of the zone heating loads independent from the weather
> file?
> > Is
> > >> > there some other reason this occurs?  Thanks in advance
> > >> > 
> > >> > Sam Roose
> > >> > 
> > >> > 
> > >> > 
> > >> > 
> > >> > 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
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 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
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> > > 
> > > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.idf and
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> > > 
> > > 
> > > 
> > > 
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> > > 
> > 
> > 
> > 
> > 
> > [Non-text portions of this message have been removed]
> > 
> > 
> > 
> > 
> > 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
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> > Yahoo! Groups Links
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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
> 
> 
> 
> 
> 
> 
> 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
> 
> 
> 
>  
> 
> 
> 
> 






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References:
- Re: [EnergyPlus_Support] Zone heating loads and heating meter not equal
  - From: Sam Roose
- Re: [EnergyPlus_Support] Zone heating loads and heating meter not equal
  - From: Michael J. Witte

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