Question-and-Answer Resource for the Building Energy Modeling Community
Get s tarted with the Help page
Ask Your Question

Design Size Vs User Defined Size

asked 2018-06-14 19:37:45 -0600

Ranjani gravatar image

updated 2018-06-15 05:12:18 -0600

I am a new user of Energy plus and Open Studio (2.5). Can I get some guidance for the following questions?-

  1. I autosized the system capacities in Open Studio and was looking at Component Sizing Summary report. I am not sure which values to use? Design size or User specified Size?

image description

  1. I used the 'Autosize measure' in Open Studio to autosize the HVAC system capacities, but it didnt work. Am I missing any step in-between? The idea is to find a quicker way to autosize the HVAC systems than manually doing it at each system level.
edit retag flag offensive close merge delete


When you say "it didn't work", what does that mean? Please provide more details.

MJWitte gravatar image MJWitte  ( 2018-06-18 10:36:45 -0600 )edit

Hi, I meant the systems weren't autosized after the simulation was complete. I exported an OSM file from CBECC-Com which already had the proposed system capacities. Instead of manually authorizing the system, I wanted to use the Autosize measure in Open Studio. Can you give me some guidance on this? Thanks

Ranjani gravatar image Ranjani  ( 2018-06-18 11:04:17 -0600 )edit

1 Answer

Sort by ยป oldest newest most voted

answered 2018-06-18 10:35:20 -0600

Most output reports are documented in detail in the Output Details and Examples document, but I see that this documentation hasn't kept pace with some of the reporting changes over time, this report included.

In general, for reporting of sizing results, "Design" values are calculated by EnergyPlus sizing, and "User-Specified" values are directly specified (e.g. hard value for a flow rate) or modified by a user input (e.g. multiplied by a sizing factor). The user inputs that impact "user-specified" values include sizing factors and flow rates in the sizing inputs (ref. Sizing:Parameters,Sizing:Zone, and Sizing:System) and hard values in the component objects.

Which values to use? Often, there will only be a "design" value reported, so that's the one to use. If both values are reported, then the "user-specified" value should be the one to use assuming that all of the inputs are correct. When the two values differ significantly, it is important to understand exactly why based on the detailed inputs in the input file.

edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer


Question Tools



Asked: 2018-06-14 19:37:45 -0600

Seen: 206 times

Last updated: Jun 18 '18