Anonymous Major Research Laboratory

A major research laboratory operating a centralized chilled-water plant across more than 5,000 acres faced a critical infrastructure challenge: its Allen-Bradley PLC-5 control system, originally installed when the plant was centralized in 1990, was nearing end of life. A planned expansion of the research grounds required adding new water chillers with modern controls, but the facility could not afford significant downtime — chilled water runs 24/7 to support active experiments and one of the largest computing centers in the country. Any loss of cooling risked interrupting ongoing research and corrupting stored experimental data.

Working with Applied Control Engineering (ACE), a Rockwell Automation PartnerNetwork Solution Partner, the laboratory migrated from its legacy PLC-5 platform to the Allen-Bradley ControlLogix industrial control system using a phased approach that kept the plant operational throughout. ACE used a Rockwell Automation system conversion tool to prefabricate ControlLogix hardware in advance, minimizing on-site transition time. The migration proceeded in three phases: first replacing the legacy controllers while adding capacity for new chillers, then expanding to two additional chillers, then adding three more and migrating the remaining legacy I/O racks. Custom I/O configurations required close coordination between ACE and Rockwell Automation to maintain compatibility with the laboratory's non-standard setup.

The phased ControlLogix migration successfully expanded the plant's chilled-water capacity from 4,850 tons to 11,100 tons — more than doubling output. Key outcomes included:

• Control loss during migration cut from 8 hours to 4 hours — the plant ran in bypass mode on stored chilled water, keeping research operations uninterrupted
• Legacy I/O rack replacement averaged one week per rack, within the allotted timeline for each phase
• Projected energy savings of ~$400,000 per year from the more efficient control system
• Research operations continued normally throughout all three phases of the migration

• Phased migrations reduce risk for critical infrastructure — breaking a platform replacement into stages allows facilities to stay operational and catch issues early rather than betting on a single cutover.
• Pre-fabricating hardware off-site compresses on-site transition windows — using vendor conversion tools to build out replacement hardware in advance is essential when maintenance windows are measured in hours.
• Standardizing on a modern, supported platform pays dividends beyond the immediate project — ControlLogix's scalability enabled chiller additions across five years without re-architecting the control layer.
• Involve the control system vendor early when non-standard configurations exist — specialty I/O or legacy customizations require vendor-level input to avoid mid-project redesigns.