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Multiple terminal units in one thermal zone in OpenStudio

asked 2017-09-27 19:26:14 -0600

updated 2017-09-29 09:55:01 -0600

First Question: I would like to have one thermal zone for the whole south side of the building serving 8 conditioned spaces with one terminal unit in each of these spaces. How could I do that?

Second Question: If I had a very large space like a whole story open office of a 400m^2 area and having assigned it into one thermal zone, how could I have 8 terminal units on this space?

As regard the second question, the reason I want 8 terminal units in one thermal zone is because I think the results (between 8 and 1 terminal unit) are totally different in many ways.


  1. One terminal unit doesn't have the same comfort results across all the space area (in a 200m^2 area), for example if I put the terminal unit in the south side of the space, definitely a person in the north side will not have the same sensible comfort result
  2. One terminal unit doesn't consume the same energy as 8 terminal units.

If I made a mistake, please let me know.

This is REALLY very strange. I give an example: Let's suppose i assign 5 different spaces(this means that there are walls between them) into one thermal zone. How can these 5 spaces be serviced by ONLY ONE terminal unit ? There must be an option of assigning number of terminal units for heating/cooling of a space. If no, logic says that i have to assign one distinct thermal zone for each of my spaces that i want to be serviced! Can someone more experienced than me in OpenStudio answer my question?

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@Julien Marrec Sorry but i was editing my question and after i have pushed save i saw as notification that you edited it also, but now i can' see what you have written.

Rafael Miliopoulos gravatar image Rafael Miliopoulos  ( 2017-09-28 08:30:19 -0600 )edit

@Julien Marrec Somewhat new to the forum. I have just found the revision history so ignore my last comment.

Rafael Miliopoulos gravatar image Rafael Miliopoulos  ( 2017-09-28 08:49:26 -0600 )edit

2 Answers

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answered 2017-09-28 07:40:06 -0600

Dinosaver gravatar image

Energy modeling software usually follows the logic when you show functionally different parts, not physically different. If your terminals are connected to the same system and follows the same control - they are functionally the same, no need to model 8 of them. If you want to model a situation when your terminal devices follow different control or are connected to different systems - then you do it as usual (not sure OS will allow you, but original E+, Design Builder and Simergy will allow you). Assigning huge areas to one thermal zone may be incorrect from reality point of view. Different parts of the same air volume will have different temperatures at the same time, and you probably want to design your engineering systems to cope with this.

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Sorry, my questions were not so clear so i edited my question. Please have a look of it. Thanks in advance!

Rafael Miliopoulos gravatar image Rafael Miliopoulos  ( 2017-09-28 08:19:14 -0600 )edit

OpenStudio as any other energy modeling software does not model your systems as they are in reality. Your comment that one terminal unit does not consume the same energy as 8 is not really correct. I mean, in the real world with the real equipment - that's true. But from energy modeling perspective it is one of your tasks to set up parameters of this one "virtual" terminal units that it represents 8 "real" units.

Dinosaver gravatar image Dinosaver  ( 2017-10-02 09:36:35 -0600 )edit

Thanks! Now i have mad it clear in my mind about the OpenStudio's logic.

Rafael Miliopoulos gravatar image Rafael Miliopoulos  ( 2017-10-02 13:51:08 -0600 )edit

answered 2017-10-02 07:47:23 -0600

You can do a couple things:

  1. Create one zone with 8 spaces and one virtual terminal unit that is the sum of the 8 terminal units (assumes that they all operate together)
  2. Create a zone for each space and include 8 terminal units (this probably leads to longer simulation time without much of a benefit in increased accuracy)
  3. If the spaces are similar enough (size, usage, etc.) create one space with a multiplier, assign one zone with one terminal unit and the results will be multiplied (similar to #2 but with shorter simulation time).
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Thanks for your response! I've already used the solution #2. Fortunately the project is not so complicated and the time simulation is ok!

Rafael Miliopoulos gravatar image Rafael Miliopoulos  ( 2017-10-02 13:53:10 -0600 )edit

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Asked: 2017-09-27 19:26:14 -0600

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Last updated: Oct 02 '17