Centra Credit Union – Retro-Commissioning (RCx)
Duke EnergyThe Challenge
Over time, the building’s control strategy had drifted into a “set it and forget it” mode: Both of the facility’s rooftop HVAC units ran 24/7, regardless of occupancy. Duct static pressure and hot water pump differential pressure were fixed, causing fans and pumps to work harder than needed. Zone setpoints, discharge air temperature, and hot water temperatures were conservative and not reset for unoccupied periods. Over time, this led to rising energy bills and unnecessary equipment wear.
The Solution
Through Duke Energy’s RCx Find-and-Fix program, Michaels Energy identified a number of low-cost control improvements, including:
- Scheduling & optimal start: RTUs now match business hours (5:00am-6:00 a.m. start, off evenings and weekends) with a one-hour optimal start, instead of running around the clock.
- Static pressure and pump differential pressure reset: Supply fan static pressure is reset between 0.75 and 1.75 inches based on VAV damper positions, and hot water pump differential pressure is reset between 10 and 20 psi, trimming fan and pump energy.
- Temperature adjustments: Wider occupied/unoccupied temperature ranges, a discharge air temperature reset (55–65°F), and a hot water temperature reset with lower unoccupied temperatures cut both electric and gas use.
- Economizer optimization: Comparative dry-bulb economizing for both RTUs improves “free cooling” hours versus fixed lockout setpoints.
Results
The combined measures deliver Centra Credit Union verified annual savings of about $27,403 in the form of 151,250 kWh and 13,480 Therms. During the study, Michaels identified future savings potential of $1,719 annually if additional measures are implemented. With controls now aligned to real occupancy and conditions, Centra has a more efficient, more flexible HQ, along with a controls platform that can support future measures such as additional fine-tuning of setpoints and sequences.
Client Feedback
“The energy review, conducted by Michaels Energy, identified opportunities to improve efficiency and reduce operating costs. Implementation of these recommendations has resulted in meaningful cost savings for Centra, while supporting longer-term sustainability objectives, and strengthening energy management practices. We appreciate the collaboration with Michaels Energy and the opportunity to see tangible results.”
—Sharon Taylor, VP Facilities, Centra Credit Union