3 Steps:

1. Enable Natural Environments and Select a valid weather file.
2. Specify valid start and end times and step size.
3. Choose an initial starting temperature for all part(s) or choose to seed the transient run with a steady-state analysis at the first time step.

Step 1: Enable natural environments and select a valid weather file.

Go to the Edit>Environ Tab.

Select Natural (Weather).

You must specify a valid weather file. Click Browse to locate the file.
ThermoAnalytics software includes several sample weather files. They are installed in the "work/weather/" directory. For example, in a typical RadTherm installation on Windows, the sample weather files would be located at:

C:\Program Files\RadTherm\Work\Weather\

The weather files are text files. You can view their contents with any text editor. Once you have selected the weather file, the start date and time will appear next to the file location. You can change the start date, which defaults to the date reflected in the file name.

You can edit the global location information, default soil type: and initially, we recommend that users use Modeled Solar inputs and Sky Temperature data. These parameters are difficult to measure and modeled data is often the better choice.

Step 2: Assign start and end times, and then select time step.

If you wish to run a solution over the full time frame of the weather file, click on the Assign button to assign the start and end times of the solution to the weather file values.

Go to the Analyze>Params Tab
Check to make sure the start and end times of the thermal solution are correct. Modify them if desired.
IMPORTANT: Choose a step size that is appropriate for your needs. The default is 0.5 minutes. If you run a large model and save results every 0.5 min, you will have a very, very large file full of results. Therefore, if you choose a short timestep, you may wish to store results only every X  number of timesteps. Just below the Solution Parameters box, you can specify "Save results every X timesteps."

For a quick run, you may wish to select a high tolerance value, allowing a faster run time with less accurate results. For example, choose "Tolerance" and set the tolerance to 0.1C or 0.1F. The results will not be highly accurate, but the run time will be shorter.

Step 3: Define the initial conditions.
In the Editor>Parts tab, you can define the starting temperature for the front and back of all parts. The default initial temperature setting is "Seed SS." This means that the whole modeling system will be allowed to come to equilibrium with all T=0 inputs (including weather) before moving to the first time step.

To define initial temperatures for each part individually, select each part in turn and select "Bypass SS." Enter the desired starting temperature for the FRONT and BACK sides of each part. The default is 20C. Note that if you have a highly conductive part and you choose different Front and Back temperatures, the simulation may "bounce" energy between the two thermal nodes.

To set all of the initial temperatures to a single value, select all of the parts using the Parts List. From the menu bar, select Window>Parts List (in Version 5 or 6, it is found under View>Parts List).

Click the "Select All Parts" button. Click "Bypass SS" and enter a value. This will affect all parts, and the BACK value will default to the value you entered. If the Current Part is a fluid or an assigned temperature part, and you do not see the Seed SS or Bypass SS, hold the CONTROL Key and click TWICE on a "calculated" temperature part in the Parts List. This procedure will make that part current, and the Front and Back tabs will be enabled.

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