RE: [EnergyPlus_Support] Design Days

There are many questions related to yours in the group mail.

If you read the I/O manual carefully, you will understand the purpose of each field in the designDay object.

In the .DDY file, there are many objects for Winter and Summer.

If you look at the title name, theres is a percentage value 0.4% 1%, .. 99.6%

The maximum drybulb temperature is taken from the weather file and compiled into statistics in the .STAT file.

The value of the max. dryBulb and the Wetbube at MD is used the third field, if WMD appears in the title.

You can make up your own later on.

There is no Winter in Singapore. So I use four DesignDay data to represent four seasons to line up the solar agnle with the building, to study the heat through windows.

If you know the purpose of using the different ones, use as many as you want. The maximum and mininum values would be used for EPlus sizing, and they are listed in the fn-Zsz.csv fnSsz.csv files.

The best way to learn is to run a few 5zone example files.

I change the sky clearance, dates, day types, etc. to simulated different local conditions withing using the weather file.

Of course, the simulation is not exactly as using the annual weather file.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: homero.noboa@xxxxxxxxx
Date: Tue, 27 Mar 2012 13:44:04 -0500
Subject: Re: [EnergyPlus_Support] Design Days

Hi Linda. Thanks for your prompt response.

Could you please tell us what happens when I include two summer design days in my model idf? Does E+ uses the worst? Uses the last? Is OK to include more than 1 design day per season?

Thanks.

Homero.

On Tue, Mar 27, 2012 at 1:26 PM, Linda Lawrie <linda@xxxxxxxxxxxxxx> wrote:

Read the design conditions section of the ASHRAE HOF (Handbook of Fundamentals).

The design days that are included with the EPW files (extension .ddy) are direct derivatives of those yearly conditions.
Sizing only uses the peak of any heating/cooling.
You could actually have a cooling peak on a winterdesign day but that wouldn't be common.

the next release after this will include monthly design conditions as shown in the HOF as well. Again, some peaks may happen at lower sun angles than the hottest months.

At 12:23 PM 3/27/2012, hnoboam wrote:

Dear List.

In many many example idfs I have seen only two design days used, one for summer, one for winter. However, in the weather file package for any site, for example for Beijing, the ddy file contains many design day definitions.
My questions are:
1. All the choices of design days are for me to choose one that I like?
2. What happens if I include more than one winter design day and/or more than one summer design day? I just did this and E+ ran, not sure what it did with the different autosized values.

Thanks

Homero

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