For those in the energy management, energy engineering, building maintenance or facilities operations industry, this task of developing a system diagram, can make a huge difference in troubleshooting issues you may have on site, or can aid in a better understanding of how a building normally operates.
The simple definition of a system diagram, is a simplified flow path diagram that shows only major components, supply/return ducts/pipes, and the regions these equipment supply (i.e. zone 1 conference room, zone 2 restroom, etc). With a solid, complete system diagram and a building energy use profile (this data can be downloaded from your local utility company, TBD on blog post for this), the energy engineer now knows pretty much everything about this building. They know how a building operates, what the hours of operation are, which loads turn on first/last, when lights are left on, whether the HVAC system is demand controlled or climate controlled, and the list goes on.
But if you’ve ever troubleshot a system, analyzed building control systems and run cycles, you know that a complete system diagram can make your life a whole lot easier. So we thought we’d come up with a simple checklist of things to help guide you along the journey to developing your first system diagram. Again, there are other great resources out there, this is simply another source to bring clarity to a fundamental part of energy engineering.
How to List:
First, start with a hand-drawn schematic. Take your clipboard, pencil and paper and walk the site. Start in the mechanical room where the boiler, HVAC and hydronic systems are usually located (all buildings differ, but most of them in California are heated via a boiler/VAV forced air configuration and electric/gas HW heater systems for domestic HW).
Start with a large component (like the air handling unit, or intake louver), and start walking the ducts to see where they end up. Go slow, read any directional signs on the ducts and piping, as you will want to put these directions on your diagram. Keep a close eye on how return air (if applicable) returns back to the AHU or makeup air handler.
Remember that there will be multiple iterations of the system diagram. You will find it’s hard to draw everything perfect on your first try. Also, have someone check your work to confirm if you’ve marked everything down correctly. Engineering is full of QC/QA checks to ensure a high standard of quality is upheld.
Utilize As-build drawings if available. It helps to have an idea of how many zones your system supplies air and water to ahead of time. Construction firms and/or contractors are required to provide as-build drawings to the client 90 days after construction has completed (or as applicable in the agreed upon contract). These come in handy when walking a building to compile a system diagram.
Here’s some photos to help show just how iterative this process is:
Hand-drawn initial system walk, my airside didn’t change much from the initial drawing.
Here’s our first attempt at the waterside (hydro) system:
You can utilize the as-builts provided either by the customer if you’re consulting or supplied to you by the designer/contractor if you’re the customer. It’s nice to use one separate highlighter colors to trace out the supply and return air ducts. In this example, we had 4 air handling units serving a small mall area with other amenities like barber, food court, freezers and such.
Pretty old as-builts can sometimes confuse people, so the most info you can get from these the better, a simple system diagram is well worth the headaches of reading through these as-builts.
The next step, once you feel you have enough info to move forward, choose a program you want to design on (PowerPoint, Word, AutoCAD, etc) – we used PowerPoint as it’s easy to email and print out quickly for our clients. Start laying out the drawing!
Here’s what we came up with:
(Airside)
(Waterside)
There will most likely be another iteration of changes to come, after the client looks it over and provides comments. Our airside was pretty straightforward, but the hydro is a little bit more complicated. We needed to really focus on simplifying the document down to the basics, which too some finagling and a lot of time. You should focus on major components, such as:
Chiller
Boiler
AHU’s (Air Handling Units)
Pumps
Motors
Valves
You can notice, we’re still working on the waterside system, as we’re missing both the chiller and 3 additional AHU’s that are supplied with both HW and Chill Water for heating and cooling. But it’s a good start for now.
Thanks for reading and we’ll provide updates once our customer has had a chance to look over our system diagram. We’ll also get into providing a final report, where you should keep it and who should know it exists in our next course: Developing a System Diagram Part 2.
Cheers
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