Quite often, this pursuit to achieve a unique system performance or energy efficient benchmark will draw a design engineer straight to some computer software and/or equipment manufacturer’s performance data. They quickly begin to look at the “big picture” results without necessarily thinking through some engineering basics such as startup, commissioning, and maintainability, as well as controllability of this innovative system.
Walk Before you Run
To be truly creative and able to think through the process, I believe the design engineer has to start with the basics:
- Create a flow diagram of the system.
- Write the sequence of operation for a guide — do not let someone else write it (refer to Back to Basics). This needs to be completed by the design engineer.
- Integrate the flow diagram with the control strategy, adding control valves, dampers, temperature transmitters, etc., as needed to complete the design.
- Be very knowledgeable of performance curves (fans and/or pumps) and equally familiar with the specific equipment performance curves for this innovative system.
- Complete heat loss and heat gain calculations.
- Determine minimum and maximum supply air, return air, and exhaust air.
After completing the above, the design engineer is now ready to use that computer software to simulate this innovative design performance. With the system simulation will come the need for input of performance data from the equipment manufacturer(s). Having started with good engineering basics, the results of the computer output can be critiqued for accuracy, based on a thorough understanding of how the system will function from maximum cooling to maximum heating.
Test Time
The design engineer isn’t finished yet. Next comes the “reality check” by having a facility engineer review the design for operation and maintenance of this innovative concept. Will the client’s technicians be capable of operating this system year in and year out? Is this great idea going to be maintainable?Analogous to giving a person a new bicycle, if they don’t know how to ride a bike, this unique piece of technology will prove to be ineffective.
As a final check, the design engineer should find another engineer to play “devil’s advocate” and review the concept and supporting data. Find another design engineer to “prove you wrong.” So often, engineering firms don’t make the time to provide a second opinion, quality assurance review, or examination of the construction documents. Firms can be too busy getting the work done to take the time to make sure it will be error-free.
When it comes to innovative hvac design, these “checks & balance” become even more important. First-of-a-kind systems can be even more important as a design firm’s reputation may be on the line. Equally important, with each innovative system is the financial investment by a customer who is counting on this design engineer to provide a successful project.
