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Re: [EnergyPlus_Support] Re: dual setpoint with deadband thermostat/furnace control problems



The predicted loads (e.g. "zone sensible load to heating setpoint predicted") 
are what the thermostat is asking for.  If they are not met in a given 
timestep, the zone temperature will deviate from setpoint and the predicted 
load in the next time step will effectively include what was not met in the 
previous time step.  So these are not valid variables to accumulate over time.  
Use the coil loads and/or "zone/sys sensible heating load" (and cooling).   

Note that in your inputs, the fan schedule is always on and the "Supply Fan 
Operating Mode = CONTINUOUS".  Any time that the thermostat is in deadband, 
"zone/sys sensible heating load" will be equal to the supply fan heat.  That is 
probably the heating that you were seeing on the summer design day.  I am 
guessing that you want the fan mode to be Cycling instead of Continuous.

Also, the default ground temperatures of 18C are probably not appropriate.  
Because this is a residential application, the ground heat loss is a 
significant contribution to total loads.  Read about ground heat transfer in 
the Input Output Reference and in the Auxiliary Programs document.

Mike


On 6 Feb 2006 at 13:25, Richard Raustad wrote:

> Add these report variables to your input file and see if the heater is 
> turning on. It's not.
> 
> Report Variable,
>     *,                       !- Key_Value
>     Heating Coil Rate,  !- Variable_Name
>     hourly;                  !- Reporting_Frequency
> 
> Report Variable,
>     *,                       !- Key_Value
>     Heating Coil Runtime Fraction,  !- Variable_Name
>     hourly;                  !- Reporting_Frequency
> 
> Report Variable,
>     *,                       !- Key_Value
>     DX Coil Sensible Cooling Rate,  !- Variable_Name
>     hourly;                  !- Reporting_Frequency
> 
> Report Variable,
>     *,                       !- Key_Value
>     Fan Electric Power,  !- Variable_Name
>     hourly;                  !- Reporting_Frequency
> 
> With these additional variables you can then compare the actual 
> cooling/heating rate to that predicted.
> 
> For heating, add the fan and the heating coil rate and compare to the 
> predicted.
> For cooling, subtract twice the fan energy from the cooling coil 
> sensible rate and compare to predicted.
> 
> I did not do an annual run but I did see 2700 watts for cooling on the 
> summer design day (38C) and
> 9000 watts for heating on the winter design day (-17C) which seems 
> reasonable.
> 
> darthskunky wrote:
> 
> > Thank you very much!  I have a few other questions if you've got the
> > time.  I changed the variables you advised, and output an hourly
> > report for the design days.  When looking at the report, there are a
> > few hours on my summer design day in which the furnace seems to be
> > heating.  I don't understand why this is, considering a) the outdoor
> > temperature is between 30 and 37C and b) I set a deadband from 20-
> > 25C.  To me, this means the heating will not come on unless the
> > indoor temperature is 20C or below.  Am I misunderstanding what the
> > output "zone/sys sensible heating rate" represents?
> > Also, when I do an annual run with monthly data, the outputs I'm
> > looking for are instantaneous sensible and latent cooling loads (as
> > well as total heating load (which I am mostly familar with in the
> > units of BTUH) and winter envelope losses and total heating load. I
> > was under the impression that the "zone sensible load to heating
> > setpoint predicted" and "zone sensible load to cooling setpoint
> > predicted" variables represented the total heating and cooling
> > sensible loads, but the numbers just don't look right to me.  25,000
> > watts of cooling for an 1800sf building?
> >
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad
> > <RRaustad@...> wrote:
> > >
> > > Change these 2 report variables to hourly and change the run
> > control
> > > object to only do the design days.
> > >
> > > Report Variable,
> > >     *,                       !- Key_Value
> > >     Furnace Fan Part-Load Ratio,  !- Variable_Name
> > >     timestep;                !- Reporting_Frequency
> > >
> > > Report Variable,
> > >     *,                       !- Key_Value
> > >     Furnace Compressor Part-Load Ratio,  !- Variable_Name
> > >     timestep;                !- Reporting_Frequency
> > >
> > >
> > > RUN CONTROL,
> > >     Yes,              !- Do the zone sizing calculation
> > >     Yes,              !- Do the system sizing calculation
> > >     Yes,              !- Do the plant sizing calculation
> > >     Yes,              !- Do the design day simulations
> > >     No;               !- Do the weather file simulation
> > >
> > > You will see that the simulation is maintaining the set points
> > > correctly. 20C in winter and 25C in summer just
> > > as your compact HVAC thermostat requested.
> > >
> > > COMPACT HVAC:THERMOSTAT,
> > >     Thermostat,         !- Thermostat Name
> > >     ,                   !- Thermostat Heating Setpoint Schedule
> > >     20.0000005298191,   !- Thermostat Constant Heating Setpoint {C}
> > >     ,                   !- Thermostat Cooling Setpoint Schedule
> > >     25.0000006622738;   !- Thermostat Constant Cooling Setpoint {C}
> > >
> > > If you make an annual run and see a time when both heating and
> > cooling
> > > occur, it is because the simulation ran at a
> > > reduced time step and you are seeing the average values over the
> > hour.
> > > Use a detailed
> > > time step to see what is happening during these times. Example:
> > >
> > > Report Variable,
> > >     *,                    !- Key_Value
> > >     Furnace Fan Part-Load Ratio,  !- Variable_Name
> > >     detailed;             !- Reporting_Frequency
> > >
> > > Make all your report variables "detailed" so the info lines up in
> > the
> > > csv file.
> > >
> > > And make the run period smaller to reduce the size of the output
> > file:
> > >
> > > RunPeriod,
> > >     5,                 !- Begin Month
> > >     1,                 !- Begin Day Of Month
> > >     7,                 !- End Month
> > >     31,                !- End Day Of Month
> > >     UseWeatherFile,    !- Day Of Week For Start Day
> > >     Yes,               !- Use WeatherFile Holidays/Special Days
> > >     Yes,               !- Use WeatherFile DaylightSavingPeriod
> > >     No,                !- Apply Weekend Holiday Rule
> > >     Yes,               !- Use WeatherFile Rain Indicators
> > >     Yes,               !- Use WeatherFile Snow Indicators
> > >     1;                 !- Number of years of simulation
> > >
> > >
> > >
> > > darthskunky wrote:
> > >
> > > > I'm modeling a fairly simple home that's around 1800 square feet
> > with
> > > > a COMPACT HVAC furnace (set up mostly to autosize.)  I've been
> > having
> > > > trouble figuring out what's going on with the thermostat, which I
> > > > believe is has a control type of dual setpoint with deadband,
> > which is
> > > > what I want. I set the heating to 68 and the cooling to 77.
> > > > Nevertheless, looking at my hourly data, there seem to be days
> > when
> > > > the heating and cooling systems are directly opposing eachother.
> > > > Would someone be willing to look at my files to see what's going
> > on?
> > > > I'm new to EnergyPlus and have been having numerous problems
> > obtaining
> > > > anything close to what seem like valid outputs.  My input file is
> > > > pretty simple, so troubleshooting might not be too hard.  I'll
> > upload
> > > > the files.  The idf is called habitatcomposite.  If someone could
> > help,
> > > > I would be incredibly grateful, as I need to get this figured out
> > > > pretty soon.  Thanks a lot!
> > > > MC
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > The primary EnergyPlus web site is found at:
> > > > http://www.energyplus.gov
> > > >
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> > > >
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> > tware+program&w3=Medical+software+program&w4=Wedding+program+software&
> > w5=Cad+software+program&w6=Maintenance+program+software&c=6&s=177&.sig
> > =eUI27kyL1-jKHpWWDj86mg>
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> > > > ------------------------------------------------------------------
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> > > >
> > >
> > > --
> > > Richard A. Raustad
> > > Senior Research Engineer
> > > Florida Solar Energy Center
> > > University of Central Florida
> > > 1679 Clearlake Road
> > > Cocoa, FL  32922-5703
> > > Phone:   (321) 638-1454
> > > Fax:     (321) 638-1439 or 1010
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> > >
> > > [Non-text portions of this message have been removed]
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> >
> >
> >
> >
> >
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> <http://groups.yahoo.com/gads?t=ms&k=Maintenance+program+software&w1=Maintenan
> ce+program+software&w2=Cad+software+program&w3=Wedding+program+software&w4=Ema
> il+software+program&w5=Backup+software+program&w6=Medical+software+program&c=6
> &s=177&.sig=1vvYeC0b-tZO57M432dQRg> 
> > 	Cad software program 
> >
> <http://groups.yahoo.com/gads?t=ms&k=Cad+software+program&w1=Maintenance+progr
> am+software&w2=Cad+software+program&w3=Wedding+program+software&w4=Email+softw
> are+program&w5=Backup+software+program&w6=Medical+software+program&c=6&s=177&.
> sig=-3yw1LK8S4-HRkLds0_2Uw> 
> > 	Wedding program software 
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> rogram+software&w2=Cad+software+program&w3=Wedding+program+software&w4=Email+s
> oftware+program&w5=Backup+software+program&w6=Medical+software+program&c=6&s=1
> 77&.sig=kZ-IchgeLCG70coAyI80VA> 
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> <http://groups.yahoo.com/gads?t=ms&k=Email+software+program&w1=Maintenance+pro
> gram+software&w2=Cad+software+program&w3=Wedding+program+software&w4=Email+sof
> tware+program&w5=Backup+software+program&w6=Medical+software+program&c=6&s=177
> &.sig=cBF2-ztpaLvnaTJPx6CBLQ> 
> > 	Backup software program 
> >
> <http://groups.yahoo.com/gads?t=ms&k=Backup+software+program&w1=Maintenance+pr
> ogram+software&w2=Cad+software+program&w3=Wedding+program+software&w4=Email+so
> ftware+program&w5=Backup+software+program&w6=Medical+software+program&c=6&s=17
> 7&.sig=5osb1n7Lxk9MOEehsYRNDg> 
> > 	Medical software program 
> >
> <http://groups.yahoo.com/gads?t=ms&k=Medical+software+program&w1=Maintenance+p
> rogram+software&w2=Cad+software+program&w3=Wedding+program+software&w4=Email+s
> oftware+program&w5=Backup+software+program&w6=Medical+software+program&c=6&s=1
> 77&.sig=xY9IJ6qMj0nggKKNjQxl0g> 
> >
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> 
> -- 
> Richard A. Raustad
> Senior Research Engineer
> Florida Solar Energy Center
> University of Central Florida
> 1679 Clearlake Road
> Cocoa, FL  32922-5703
> Phone:   (321) 638-1454
> Fax:     (321) 638-1439 or 1010
> Visit our web site at: http://www.fsec.ucf.edu
> 
> UCF - From Promise to Prominence: Celebrating 40 Years
> 
> 
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> The primary EnergyPlus web site is found at:
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> 
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> 
> Attachments are not allowed -- please post any files to the appropriate folder
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> "search" button.
>  
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> 
>  
> 
> 
> 
> 
> 


========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx





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