RE: [EnergyPlus_Support] Re: Is it possible to ask e+ for an output of only 1 specific day?

This is not an easy question to answer.

You can set the time step to one, so the output may only have data at hourly intervals. The number of output data is reduced.

But it does not mean that the time needed for calculation is also reduced, because a large chunk of air is extracted and filled in a zone may cause the temperature to change more per step, and take longer to converge. The result may be oscilating and diverge, and cause the system to crash. The condition depends on the internal load size, thickness of wall materials, and many other factors. Too small a timestep is also no good for thick walls.

When the result is displayed at hourly interval, the value is averaged over a longer time, therefore, the 'quality' may be reduced.

I use timestep 6 most of the time. (10 mins interval..) I like to see the value chage and settle, whenever a schedulve value or the input is changed.

You can run the simulation at 10 min intervals and still display the output data hourly or mixed.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: motabmx1@xxxxxxxxx
Date: Fri, 28 Oct 2011 16:11:48 +0000
Subject: [EnergyPlus_Support] Re: Is it possible to ask e+ for an output of only 1 specific day?

I have another question,

in the timestep object I have specified 2 instead of 4 as recommended by e+, I did that so the information in output variable is reduces to half-hour intervals. Is this correct? or the time step object will have an effect in the quality of the results

thanks all for yours replies

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
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> The problem is not with EPlus. Which day do you want and why? If you wanted to see the output on any day, just scroll the ResultViewer to the day you want. Some display program would give you the values as you move the cursor line to that time value. If you run only the DesignDay or the one day weather file, be careful. The single day or a few days result may have some initialization error for the first few days. So you will have to choose multiple runs and view the second or third sets of results. Repeat more times, if they are not the same. I can view the whole year's result at hourly or 10 minute intervals on a spread sheet plot as well. RVI selects the items to display, the rows show you all the data for the timestep. You can see up to 800 data points on each display screen. (one pixel per row.) This is what post processors are for.
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> Dr. Li
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: motabmx1@...
> Date: Fri, 28 Oct 2011 13:41:51 +0000
> Subject: [EnergyPlus_Support] Is it possible to ask e+ for an output of only 1 specific day?
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> hi all,
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> anyone knows if it is possible to ask for only one day from the outputs
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> I would like to not have to go through out all year when I am only intersted in the internal room temperature of one zone at one specific day
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> thanks all
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