Re: [EnergyPlus_Support] warm-up time

[Rick Strand <rkstrand@xxxxxxxx>]

As Ned and Dru have already mentioned, E+ does have a warmup period during 
which the program will iterate on the same day until it reaches 
"convergence".  For a design day environment, E+ will use the design day 
and repeat it until it reaches "steady periodic" conditions.  For a weather 
environment, E+ will use the first day of the weather file for the warmup 
period.  Once convergence is reached in any of these cases, it will then 
start the simulation time clock.  Note that it reinitializes temperature 
histories between different weather environments (individual design days or 
weather files) to the same starting initial condition before it starts the 
iterative warmup process.

As Ned suggested, if one wants to see how the building reacts to several 
days of extreme conditions, add an additional "normal" day to the weather 
period.  The results should show the temperatures/loads drift, with the 
amount of drift obviously a function of building type, materials, location, 
weather, etc.

Rick Strand

At 08:53 AM 3/11/2004, Edward Lyon wrote:
>As I understand the startup of an E+ calculation, the program must
>iterate to a repeatable starting condition before moving into the actual
>calculation.  Consequently, if you try to model single days (like just a
>design day), your model will always look like the conditions have been
>the same for a long time.  To see what you want, you probably need to
>calculate several days with the first days being your cool weather and
>the last days being your hot weather.  You should then see the building
>respond to a quick warmup.
>
>Ned Lyon
>
>Senior Project Manager
>Simpson Gumpertz & Heger Inc.
>
>41 Seyon Street
>Building #1, Suite 500
>Waltham, MA  02453
>
>Phone:  781-907-9000
>Fax:  781-907-9009
>
> >>> mohitmehta1@xxxxxxxxx 03/11/04 12:38 AM >>>
>
>hi:
>
>if am running a simulation of a high mass NV building between aug 14 -
>17 (4 hot days) - shouldn't the building take a few hours or days to
>warm up? like indoor and outdoor temperatures starting out the same on
>the first day (aug 14), and indoor air temperatures climbing gradually
>over the four-day period; finally balancing out? it appears that the
>mass starts out as preheated (warmed/cooled). does it use 3-4 warm-up
>days before the days that i am looking at are reported?
>
>thank you.
>
>~m
>
>
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