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Re: [EnergyPlus_Support] Weather file & Design Day

On 19 Nov 2002, at 15:32, HSIEH Chun-Ming wrote:

> 1.We know that autosizing uses only design days to make it's
> calculations. But how does the value in design day we input affect the
> simulation results? Or say that why autosizing can't calculate
> directly from data of the weather file? Is there any conflict between
> weather file and design day when I set the "Run Period" and "Design
> Day" to be the same day?

There is no conflict if you want to specify the same day.  The design 
day conditions are determined by the user specified values in the 
desing day object(s).  Design days can be used for sizing and may 
also be simulated in full (see the RUN CONTROL object).

A RUN PERIOD takes data from a weather file.  Typically design days 
are set up to represent extreme conditions for sizing equipment, but 
the weather files are constructed to represent a typical year.  A RUN 
PERIOD which matches the date of your design day will use the 
conditions for that date from the weather data file, and this will 
not match the conditions in the design day description.

> 2. We always can see a couple of data for DesignDay. One is for summer
> and the other is for winter. If we only simulate the summer condition,
> then we don't need the DesignDay data of winter. Am I right?

The sizing routines will run all of the design days present in the 
input file and use the maximum cooling and heating loads to size the 
equipment.  You may use only one design day if desired.  However, 
version will crash sometimes for equipment which is sized 
to zero capacity.  This has been fixed for the next release, but you 
may need to include a heating design day to avoid this problem.

> 3. In the infiltration object, E+ has a basic equation to do
> calculatition. Infiltration =  I * F
> *[A+B(T1-T2)+C(windspeed)+D(windspeed)] Where is the windspeed value
> from?
>  From Weather file or using the value we input in the Design day?

For a Design Day simulation the value is from the design day object, 
for a Run Period simulation the value is from the weather file.


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