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Re: [EnergyPlus_Support] RunPeriod vs. DesignDay
The statistics for design conditions may not be from
30 years... the data for many of the locations outside
the US in the ASHRAE 2001 Fundamentals are for
a much shorter period-- usually only 13-20 years.
(A recent ASHRAE research project found that at
least 13 years of data were necessary to result in
reasonable design conditions.)
To make it easier, the EnergyPlus Weather Converter
now automatically creates the design day data in IDF
format (.DDY) if the location was included in the ASHRAE
Fundamentals. Check out the .DDY files included
in the .ZIP files for each of the EPW files on the EnergyPlus
web site. Using a text editor, you can just cut and paste
the DDY into your IDF.... www.energyplus.gov/weatherdata.html
NOTE! The DDY has MOST BUT NOT ALL of the design
data you'll need... see the files for more information.
Also--the DDY includes all 11 design day combinations
that are possible from the ASHRAE Fundamentals--you
probably would want to choose fewer!
"Michael J.
Witte" To: EnergyPlus_Support@xxxxxxxxxxxxxxx
<mjwitte@xxxxxxxx cc:
> Subject: Re: [EnergyPlus_Support] RunPeriod vs. DesignDay
03/13/2003 05:24
PM
Please respond to
EnergyPlus_Suppor
t
Ming:
No, it would not be the same. Run Period data is taken from a
weather data file and will almost always not be the same as the
design day data. The design days in the datasets are single days
statistically determined from 30-yr weather data to be used for
equipment sizing. The weather files are a collection of actual
months from a similar (often the same) 30-yr data set. Also, for
autosizing equipment, design days are required. You cannot autosize
based on data from a weather file.
Mike
On 13 Mar 2003, at 22:06, waspoorboy wrote:
> Hi,
>
> RunPeriod defines a period of time for simulation.
> (ex.3/13/2003-4/13/2003)
> DesignDay is an "user created" day (weather) data for simulation.
> ------------ I guess there're different aspects for using these two.
> But I don't quite get it. (To me, in some sense DesignDay is just one
> or more selected day(s) from RunPeriod) ------------ In
> 1zoneuncontrolled.idf, two DesignDay are used. 1/21 and 7/21. Is it
> equivalent to use the following instead ? RunPeriod 1/21-1/21 and
> RunPeriod 7/21-7/21
>
> Thanks,
> Ming
>
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