Ballroom Air Handling Unit Scoping Exercise
This virtual AHU has 21 opportunities for improvement; can you find them?
This exercise lets you practice your existing building commissioning scoping skills on an air handling system serving the main ballroom in a large, high rise hotel. The exercise can stand on its own, but it was originally designed as a follow-on to the Chilled Water Plant Scoping Exercise. So, if you have not tried the Chilled Water Plant Scoping Exercise, then you should take a minute to read the Setting the Scene portion of that exercise because there are some pieces of information there that create context for this model, like the type of day it is outside and what's going on at the central chilled water plant at the time for instance.
To get you started, the next section provides a few leading questions to be thinking about as you explore the air handling system. As was the case for the leading questions in the Chilled Water Plant Scoping Exercise, there are reasons for the questions; for instance, it's possible that they lead you to clues. But if you want to simply jump right in, click here to go to the bottom of the page where you will find the files you need to work with. This link takes you to the SketchUp Resources page if you have not already been there, which has copies of SketchUp you can download and other information about working with the models.
Since this is an air handling system, psychrometrics could come up. So you may find a psych chart to be useful and this link takes you to a place where you can download a free one that will allow you to do the basics along with instructions about how to use it.
To get you started, the next section provides a few leading questions to be thinking about as you explore the air handling system. As was the case for the leading questions in the Chilled Water Plant Scoping Exercise, there are reasons for the questions; for instance, it's possible that they lead you to clues. But if you want to simply jump right in, click here to go to the bottom of the page where you will find the files you need to work with. This link takes you to the SketchUp Resources page if you have not already been there, which has copies of SketchUp you can download and other information about working with the models.
Since this is an air handling system, psychrometrics could come up. So you may find a psych chart to be useful and this link takes you to a place where you can download a free one that will allow you to do the basics along with instructions about how to use it.
Setting the Scene
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Having observed the central chilled water plant under load on a cool foggy day, You decide to head out to a mechanical room with the chief, her HVAC technician, and the utility program representative to see what one of the loads on the system is doing. The chief suggested the Ball Room AHU because they recently had a balancer come in and verify its total flow and the 25% minimum outdoor air setting.
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The mechanical room where the unit is also located on the first floor, but about 250 feet away from the plant at the opposite end of the building. As you head down towards it, the chief mentions that she knows the unit is doing a pretty good job in terms of delivering the targeted Ballroom condition of 72°F because on the way down to the plant to meet up with you, she and her technician checked it out themselves.
The opening session of the Building Commissioning Association Conference is taking place in one half of the ballroom today and the last thing she wanted was a room full of 250 or so commissioning engineers with something to complain about with regard to building system performance. She also mentions that the other half of the room is not in use. When you ask her how typical that is, she thinks about it for a minute and says it probably is how the room is used for 30-40% of the 5,000 or so hours a year the system operates. She says she can get you a more exact number from event planning if you think that would be a useful piece of information.
The opening session of the Building Commissioning Association Conference is taking place in one half of the ballroom today and the last thing she wanted was a room full of 250 or so commissioning engineers with something to complain about with regard to building system performance. She also mentions that the other half of the room is not in use. When you ask her how typical that is, she thinks about it for a minute and says it probably is how the room is used for 30-40% of the 5,000 or so hours a year the system operates. She says she can get you a more exact number from event planning if you think that would be a useful piece of information.
A Few Leading Questions
- What is the supply air temperature from the system and is it what you would expect it to be based on the information you have available to you?
- Trace out the path that a cubic foot of outdoor air takes as it makes its way from outside the building, through the system and back outside of the building again.
- What type of system is this (constant volume, variable volume, multi-zone, reheat, etc.)?
- Is AHU the hot water coil a reheat coil, a preheat coil, or a warm-up coil? Explain the reasoning behind your conclusion.
- Assess the economizer in terms of its current operating state and its ability to perform the intended function. Explain your your conclusions and what you think the implications of what you observe might be.
- What is the efficiency of the filters provided in the system?
- Is there a load on the chilled water coil? Explain how you reached your conclusion.
- What would you estimate that the relative humidity is in the ball room at the time you are looking at the system? Explain how you reached your conclusion.
- Are there any design review lessons to be learned from the installed configuration of this system? If so, what are they and why do they matter?
- What are some of the opportunities to improve performance, or save energy and resources that you observed?
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To do the exercise, you will need a version of SketchUp running on your computer as discussed on the SketchUp Resources page. Once you have SketchUp installed and running, you should be able to down load the file with the model in (the first file to the right) and begin working with it. You may also want to download a copy of the scene guide (the second file to the right).
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The model has been back-saved to SketchUp version 8, so as long as the version you are using is that one or newer, it should open up.
As was the case for the chilled water plant exercise, all of the opportunities you can discover in the model have what I call "obvious indicators" associated with them. You can take a look at the introduction to that model for more information on what I mean by that if you are not familiar.
Once you have made your list, you can download my finding list (the third file called "Answers" in the group of files above) and compare it to yours. In addition to listing the findings, the answer file tells you:
I should mention that for this particular model, the missing insulation on the piping drops to the coils is not really a finding. It's just a detail I have not finished on the model and eventually, the lines will be fully insulated.
As is the case for the other models, eventually, we hope to develop a track for each of the findings that will get into the details of how to assess it, how to do the math, now to implement the improvement, and how to verify that what you did is working. So check back occasionally to see how we are progressing on that lofty goal.
But meanwhile, try your hand at scoping out the air handling system and see what you find in terms of opportunity to save pretend energy and make pretend improvements. Hopefully, you'll have some fun, learn something, and gain a bit of confidence that carries you out in the field to do the real thing and help us solve the problems we face in the world today.
As was the case for the chilled water plant exercise, all of the opportunities you can discover in the model have what I call "obvious indicators" associated with them. You can take a look at the introduction to that model for more information on what I mean by that if you are not familiar.
Once you have made your list, you can download my finding list (the third file called "Answers" in the group of files above) and compare it to yours. In addition to listing the findings, the answer file tells you:
- What the obvious indicator is,
- What scene numbers are associated with the finding,
- What type of benefit is associated with the finding,
- What the next steps would be in terms of developing the finding, and
- What are the precautions and other considerations you should be thinking about as you move forward.
I should mention that for this particular model, the missing insulation on the piping drops to the coils is not really a finding. It's just a detail I have not finished on the model and eventually, the lines will be fully insulated.
As is the case for the other models, eventually, we hope to develop a track for each of the findings that will get into the details of how to assess it, how to do the math, now to implement the improvement, and how to verify that what you did is working. So check back occasionally to see how we are progressing on that lofty goal.
But meanwhile, try your hand at scoping out the air handling system and see what you find in terms of opportunity to save pretend energy and make pretend improvements. Hopefully, you'll have some fun, learn something, and gain a bit of confidence that carries you out in the field to do the real thing and help us solve the problems we face in the world today.
