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DesignBuilder simulation-time

asked 2018-10-24 18:03:24 -0500

Anna gravatar image

updated 2018-10-24 19:15:24 -0500

Hi All,

How much time do you expect a simulation (15,000 sf, 20 zone, 16 HVAC systems, 6 time step/hour) would take in DesignBuilder? A relatively simple building...

I have a configuration that is slightly below the requirements

and are wondering how much improvement in simulation time I could expect if I would upgrade the machine.

Any suggestions are greatly appreciated. Thank you

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answered 2018-10-25 02:26:36 -0500

Dave gravatar image

Hi Anna, you will no doubt appreciate that this is a fairly subjective question and there are a variety of factors that can affect simulation time. I would suggest you raise a support ticket and ask this question of our tech support team, as their extensive experience of reviewing models and the machines that run DesignBuilder are likely to give them a sense of this.

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Thank you, Dave. I've raised the ticket. I'm just really looking for some rough estimate, that would help me figure out if upgrading the machine makes sense. I'm experiencing a run time of 15-20 minutes for this small project, which is longer than what I would expect based on some past simulations I've done in EP-Launch. I like DesignBuilder so far, but looking for the ways to use it more efficiently, if possible.

Anna gravatar imageAnna ( 2018-10-25 09:26:55 -0500 )edit

answered 2018-10-26 08:43:46 -0500

mikesweeney gravatar image

In my experience DesignBuilder's runtime is very close to EP Launch.

-Have you tried exporting the IDF from DesignBuilder and then running it in EP Launch to test out whether this is a DB or an EP issue?

-Have you ensured that you're running the simulation at the same timestep and shading calculation period?

-Are you using the simulation manager or just running directly within DesignBuilder? The simulation manager might not be faster but it allows for 3 simulations at a time and runs in the background so it reduces the headache of long simulation times.

One other quick thought from experience, without knowing the details of your model - the addition of perimeter radiation can drag down simulation time quite a bit in comparison with other hvac controls that would seem comparably complex to model. If you do have perimeter radiation, try switching up the type (i.e. radiator to convector or vice versa) and seeing if it impacts the simulation time.

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I takes 7 minutes to run the IDF in EP Launch, which is two times faster than running the same model in DesignBuilder. I'm using 6 time steps per hour and shading calculation period of 20 days . Can you please explain what you mean by " the same timestep and shading calculation period". I'm not using Simulation Manager but will definitely explore that option. HVAC is very simple: VAV system with PFB, no radiant heating. Thanks !

Anna gravatar imageAnna ( 2018-10-27 06:23:05 -0500 )edit

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Asked: 2018-10-24 18:03:24 -0500

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Last updated: Oct 26 '18