[EnergyPlus_Support] Re: Dry bulb differs from EPW to Output Report

["frorv" <m0rph3r@xxxxxxxxx>]

That makes total sense.

Thank you very much, Linda Lawrie!

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Linda Lawrie <linda@...> wrote:
>
> This is expected. The difference comes from interpolating hourly weather data
> for subhourly timesteps in EnergyPlus. In an hourly weather file, the
> temperatures and other state-point readings are the value at the time the
> reading was taken. For example, in the USA_IL_Chicago-OHare_TMY2.epw file, the
> outdoor dry bulb value for July 2, hour 1, is 19.4C. This is the temperature
> at 1:00 am.
> 
> If you set TIMESTEP IN HOUR = 1, then EnergyPlus will report 19.4C for 07/02
> 01:00 and will use that value for the entire one hour timestep.
> 
> If TIMESTEP IN HOUR = 4, then 19.4C is used only for the time step which ends
> at 01:00. The other timesteps use linearly interpolated values between the
> hourly weather file values. When you report at the "hourly" frequency in
> EnergyPlus, you see the average temperature over the hour. If you report at
> the "timestep" frequency, you will see the values from the weather data file
> appear at the last timestep of each hour.
> 
> At 08:04 AM 4/6/2010, frorv wrote:
> >Fellow E+ users,
> >
> >I used an EPW file along with an example file provided with E+ and 
> >chose as an output report variable the 'Outdoor Dry Bulb' hourly. It 
> >happens that the temperatures are different in the weather file and 
> >in the output results... for example:
> >EPW -> E+
> >8.1 -> 7.1
> >7.4 -> 7.7
> >6.6 -> 6.9
> >
> >I am using E+ v4.0.0, but I also tried with v1.2.2 and the results 
> >are similar!
> >
> >Is this normal?
> >If so, why does it happen? If not, how do i avoid it?
> >
> >Thank You and Best Regards,
> >FrOrv
> >
>




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