A school in Berkeley County School District was facing a costly and persistent HVAC issue: repeated failures of compressors and their associated variable frequency drives (VFDs) in its dedicated outdoor air units (DOAUs).
System Overview
The facility’s HVAC infrastructure includes:
- 105 water-source heat pumps (WSHPs)
- 9 DOAUs controlled by controllers with expansion modules from one of the big 3 HVAC vendors
- 3 air handling units (AHUs)
- A condenser water loop with cooling towers, boilers, and two condenser water (CW) pumps
The Problem
From the time the school opened, the DOAU compressors and VFDs required frequent replacement. After investigation, the district’s HVAC team identified the root cause: overly aggressive modulation control from the existing controllers.
Rapid ramp-up and ramp-down of compressor signals were placing unnecessary stress on mechanical components, leading to premature failures.
Bringing in a Specialist
To resolve the issue, the district partnered with Insight Comfort Solutions LLC, a South Carolina-based controls contractor led by Chris, a BAS professional with over 25 years of experience across multiple platforms.
“The customer initially asked if I could take over just the compressor modulation signal,” Chris explained. “But once we reviewed the system capabilities, it became clear we could deliver a much more complete solution.”
Rethinking the Control Strategy
The original plan was a partial retrofit using a Contemporary Controls BASpi-Edge controller. However, after evaluating system requirements and future flexibility, the scope evolved into a full DOAU controller replacement.
At that point, Chris selected the BAScontrol-E36, which provided:
- Sufficient onboard I/O for the application
- Dual Ethernet ports for network flexibility
- Native BACnet MS/TP support
The final architecture included:
- BAScontrol-E36 as the primary controller
- A BMT-DI10 expansion module connected via MS/TP
- A 10-inch EasyIO touchscreen for local visualization
A point-for-point I/O takeover was performed, replacing the existing control logic entirely.
The Result
The impact was immediate and measurable. The Master HVAC Mechanic for the school district said, “The system runs so much better. We were able to slow the compressor modulation down, so it reaches setpoint smoothly and then just cruises.”
By eliminating aggressive control behavior, the new system reduces mechanical stress, stabilized operation, and is expected to significantly extend equipment life and provide cost savings.
Takeaway
This project highlights a common issue in BAS retrofits: control logic—not just hardware—can be the root cause of equipment failure.
With the right controller and tuning strategy, even complex systems can be stabilized without major mechanical changes.
“Contemporary Controls was instrumental to the success of this project,” Chris added. “When I encountered a few minor bumps in the road, their technical support team was on top of things and resolved the issues in a timely manner.”
