Advancing Technology in Upgrading or Replacing Vintage Low-Voltage Motor Control Centers

Low-voltage motor control centers (LV MCCs) are universally applied in the process industries. These electrical assemblies are perhaps one of the most dynamic in the industry, ever-changing as the low-voltage motor loads are constantly added and modified in response to necessary process revisions and upgrades. As existing LV MCCs approach 40-50 years in age, industry users are challenged with a decision either to replace vintage motor control centers (MCCs) at their end of life or consider to upgrade existing assemblies. This article will discuss the upgrade versus replace alternatives, addressing Underwriter's Laboratories 845 North American industry standard requirements and how this affects the design, installation, and maintenance of both upgraded and new MCCs. Application issues including considering the cost of replacing load cables versus the reuse of existing cables, high-resistant ground systems and opportunities for process improvements, and network communications that leverage the latest technology will be discussed. Finally, a case study comparing the replacement of an existing MCC versus a field upgrade based on changing out all exiting starter and feeder circuit breaker units including an estimate of the total installed cost for both alternatives for this application will be reviewed.