A school campus in South Carolina was facing a costly and persistent HVAC issue: repeated failures of compressors and their associated variable frequency drives (VFDs) within its dedicated outdoor air units (DOAUs).
Since the facility was commissioned, the DOAU compressors and VFDs have required frequent replacement. A detailed investigation identified the root cause as overly aggressive modulation control from the existing control system. Rapid ramp-up and ramp-down of compressor signals were placing excessive stress on mechanical components, leading to premature failures.
Replacing the existing controller with a Contemporary Controls BAScontrol-E36 stabilized operation, reduced equipment stress, and lowered maintenance costs.
System Overview
The facility’s HVAC infrastructure included:
- 105 water-source heat pumps (WSHPs)
- 9 DOAUs, controlled by controllers with expansion modules
- 3 air handling units (AHUs)
- A condenser water loop with cooling towers, boilers, and two condenser water (CW) pumps
Bringing in a Specialist
To resolve the issue, the school district partnered with Insight Comfort Solutions LLC, a South Carolina-based controls contractor specializing in building automation systems (BAS).
“The customer initially asked if I could take over just the compressor modulation signal,” said Chris, the Insight Comfort Solutions LLC contractor who led this project. “But once we reviewed the system capabilities, it became clear we could deliver a 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, the contractor selected the BAScontrol-E36 controller, 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 system runs so much better,” said the master HVAC mechanic for the school district. “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 reduced mechanical stress, stabilized operation, and is expected to significantly extend equipment life and provide cost savings.
Key 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,” the contractor said. “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.”
