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Disable zone/plant/system sizing

asked 2015-02-17 11:02:04 -0500

LSurf gravatar image

updated 2015-04-13 13:37:00 -0500

Under the simulation setting / simulation control, Openstudio provides the option of disabling sizing calculations. I need sizing calculations disabled, since they interfere with other components of my system.

Despite the OpenStudio settings, in the resulting idf-file sizing is enabled.

I figured this would be because some components required autosizing. I went through the process of editing the .idf-file to disable sizing, running it, filling in the missing data in OpenStudio. Now the model runs fine in E+ without the sizing, however OpenStudio still enables it.

The only workaround I can think about is disabling the sizing in the .idf-file by using an energyplus-measure.

Are there any other parameters I should check, or is there some other way of permanently disabling sizing in OpenStudio?

OpenStudio Settings

Resulting .idf

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answered 2015-02-17 15:31:57 -0500

OpenStudio has some logic in the osm -> idf code that says if there are zones and design days then turn on zone sizing no matter what. This is because OpenStudio is expecting there to be (autosized) equipment, and therefore will always write out a Sizing:Zone object if there is zones with equipment or ideal air loads.

The idea is to avoid the possibility of having a failed simulation, but clearly there are some cases where this is getting in the way. @MatthewSteen just filed an issue. I'm thinking maybe we need to relax the heavy handed override.

I'm still not completely clear why this is getting in the way of your simulation. I understand it adds some simulation time, but I can't grasp why it is negatively impacting simulation results unless you have autosized equipment bolted to the zone, in which case you would need the zone sizing simulation anyway.

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Thanks a bunch. Deleting the design days seems to do the trick. Openstudio now fails on the next issue, so I'll get to fixing that.

For deleting the designdays, there's no option in OpenStudio. I tried creating an empty ddy-file, which didn't work. What did work was to directly delete the design days from the .osm-file.

LSurf gravatar imageLSurf ( 2015-02-18 05:46:54 -0500 )edit

answered 2015-02-17 12:08:07 -0500

updated 2015-02-17 12:08:25 -0500

I don't know of another way to disable sizing, but here is the EnergyPlus measure I wrote to override the SimulationControl object with user-input options for zone, system, and plant sizing.

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Thanks a lot for sharing. For now, your measure doesn't run on my machine. (Ruby complains about not finding an in.idf)

If the other route fails I'll dig deeper in your measure. I'll certainly keep it in my liblary!

LSurf gravatar imageLSurf ( 2015-02-18 05:48:50 -0500 )edit

Interesting. It's an EnergyPlus measure, so it should be added as such to the 'Measures' tab in OpenStudio (or PAT). If you hadn't already, I would try to open a new measure by opening Apply Measure Now and clicking the icon for 'Create a Measure from Template and Add to My Measures'. Name the measure 'Apply Simulation Control' and set measure type to 'EnergyPlus Measure', then 'Create Measure and Open for Editing'. Copy and paste the text from the file I posted into measure.rb and save. It should then show up in the Library pane of the Measures tab under whatever Taxonomy group you assigned.

Eric Ringold gravatar imageEric Ringold ( 2015-02-18 08:36:54 -0500 )edit

Aah, there's my answer. I had accidentally added it as an OpenStudio measure. Thanks!

LSurf gravatar imageLSurf ( 2015-02-19 02:38:35 -0500 )edit

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Asked: 2015-02-17 11:02:04 -0500

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Last updated: Feb 17 '15