System Diagrams: Practice Making a System Diagram

Welcome to my virtual, variable flow, primary-secondary chiller plant.


I’ve been working on creating a model of a central plant in SketchUp for a while now so I can use it as a teaching tool and the image above is the current state of affairs.  There still is quite a bit of work to do, but its to the point where I have started using it in class on occasion.  

A Self-Study Exercise on Making a System Diagram

One of the things I use the virtual central plant for is to let the students make a system diagram of the portion of the plant that is shown above.  To set up the exercise, I give a little tour of the plant during which we deduce what the design intent might have been based on clues provided by the details of the machinery.   Then, I give everyone some time to make their diagram.

After that, I show them how I would go about making a diagram and what my answer might look like.  Then we explore how a variable flow primary-secondary plant works using the system diagram.  In the course of doing that, we discover that minor details in how the piping is arranged can make a huge difference in how the plant works, something that is much easier to see on the system diagram than standing in the middle of the maze of pipes.

In a recent class, the schedule got compressed and I was not able to do the “full meal deal” version of the exercise.  So, I decided to take advantage of modern electronics and make a version I could put up on the web for both the class attendees and others to access. 

I use this post to set up the exercise, including given the tour of the plant in the video clip that is embedded below.

After that, I provide links to screen shots of the model as well as the model itself so you can download them and try your hand at making the system diagram.

Once you have done that, you can go to the next post in the series and I will walk you through how I would go about developing my system diagram, and what my answer looks like.  I will then use the diagram to illustrate how a variable flow chilled water plant works, including some of the operational issues that can come up if the plant is not piped to match the design intent.

The Video Tour

So with out further elaboration, here is the video.  Once you watch it, past down for the links to the resources you need if you want to try your hand at developing a diagram.

Tour the Virtual Chilled Water Plant by Watching This Video (about 32 minutes)

The Resources

  • Click here to be taken to a file that contains enough screen shots of the plant to allow you to try making the chilled water diagram, along with the instructions you saw in the video.
  • Click here to get the actual SketchUp model if you want to be able to wander around in the plant and take a closer look.
  • Click here to download a copy of Sketch Up.  Its free and everything I did to create the plant can be done in the free version.  Its also fairly intuitive to use and there are a lot of great tutorials out there about how to use it, including one on how to move around in SketchUp, which is all you need to know to look at the plant in the model


David Sellers
Senior Engineer – Facility Dynamics Engineering

Click here for a recent index to previous posts

This entry was posted in Chillers and Chilled Water Systems, System Diagrams. Bookmark the permalink.

2 Responses to System Diagrams: Practice Making a System Diagram

  1. Chris Cox says:

    Every time I visit your website I despair at the infinite number of things I don’t know that I wish I did. Thank you for taking the time to share.

    • Thanks for visiting Chris,

      I’m just sharing things that others (and a few building systems) took the time to share with me. One of the things I like about this business is there is always something to learn. In some ways, I think the more we learn, the more we realize that we don’t know and the more amazing it all is. So, in some ways, its a blessing to realize there is more to learn and you have the curiosity and drive and opportunity to learn it. But I also know that some days that can seem overwhelming.

      In any case, I appreciate your visiting and the thanks.


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