[TRNSYS-users] reading EP weather data

Jeff Thornton thornton at tess-inc.com
Thu May 26 11:09:02 PDT 2005

At 04:35 AM 5/26/2005, Adriana Angelotti wrote:

>I'm using type 89 mode -3 to read EnergyPlus weather data (an epw file).
>Time step is 1h.
>It seems that type 89 shifts and interpolates all data (except solar 
>radiation data), as in the example
>you can read below. Is it correct? What does it mean?
>Thank you for helping.


It's important to realize that the outputs from TRNSYS components are (and 
should be) the average value over the timestep, not the value at the end of 
the timestep.  Energy+ files contain instantaneous values of ambient 
temperature.  Looking at the Energy+ data you provided, the temperature was 
4 degrees at midnight and 1.2 degrees at 1 am.  Using simple linear 
averaging, the average temperature over the period of midnight to 1 
a.m.(recorded as hour 1 by TRNSYS) is then (4+1.2)/2 or 2.6 degrees; 
exactly that provided by Type 89.  I hope this helps.


Thermal Energy System Specialists (TESS)
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