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Alternatives to Power Control Switchgear Replacement

Aging, undersized, or obsolete switchgear does not always require outright replacement. This article summarizes approaches for increasing the reliability, functionality, maintainability, and capacity of existing paralleling switchgear in backup power systems.

Background Information

Power control switchgear is essential to the proper function of backup power systems in larger facilities. Used across diverse applications including healthcare, information technology, commercial buildings, and industrial plants, these systems offer robust and sophisticated control for connecting multiple power sources and electrical loads to bus. For more information on their design and function, review the ASCO Power Technologies white paper entitled Power Control System Basics.
Options for Updating Gear

The effective service life of power control systems and paralleling switchgear can often be maximized by completing key modifications. Common upgrade strategies can often be used in lieu of outright replacement. Four approaches include:
  1. Component Replacement
  2. Door-and-Panel Replacement
  3. Control Segregation
  4. Program Upgrades
The following sections summarize these options as well as considerations for expanding the capacity of an existing power control system.

Component Replacement

Component replacement is the simplest and most direct type of modification. It is used to replace worn or malfunctioning devices as well as older components that are no longer supported by their manufacturer. Legacy components are replaced directly with new units and the system retains the same level of functionality.

When considering component replacement, it is important to evaluate whether the scope of the project will require a more comprehensive approach or an alternative strategy. Changing operating sequences or transition types, adding Supervisory Control and Data Acquisition functions, adding redundant components, and enlarging capacity are all reasons to consider whether system replacement is warranted to meet facility needs.

Door-and-Panel Replacement

“Door-and-panel” projects replace all monitoring and control components mounted on doors and interior panels within switchgear, and reuse existing structures, circuit breakers, bus work, current transformers, and mechanical equipment. New component arrangements are factory-engineered to a customer’s specification, then the equipment is installed and wired on new doors and panels before it is shipped from the factory. At the job site, technicians remove old equipment, install the new doors and panels, connect the wiring, and test the upgraded equipment.

This approach minimizes installation time and operational disruption, while providing a comprehensive solution that can provide features and functions similar to a factory’s newest designs. In addition, upgrades can include bus optimization to manage loads, hardwired backup components, large touchscreens with the latest monitoring and control software, and redundant master programmable logic controllers. Door-and-panel projects can also incorporate operating sequence changes or provide communications to other power management systems.

Control Segregation

Control Segregation involves disconnecting switchgear devices from their existing control devices and connecting them to new controls in a custom-engineered equipment frame or lineup. This approach is also suitable for changing operating sequences and adding new control and communication functions.

To complete this work, new sections containing updated equipment are designed, manufactured, and tested at the factory, then installed at the facility. Custom interconnect panels are also fabricated at the factory and to the legacy switchgear sections. Common feature additions include: (1) capabilities that keep only needed generators online; (2) capabilities for connecting prioritized loads; and (3) adding control touchscreens equipped with the latest software features.

As with the other modification strategies, control segregation upgrades can be completed for a fraction of the cost of replacing an entire paralleling switchgear system. Nevertheless, the new equipment requires additional floor or wall space.

Program Upgrades

New capabilities can sometimes be provided by changing or expanding operating sequences in power control systems. This can be completed by developing new software and installing it into existing hardware. This approach involves thoroughly evaluating facility requirements, existing sequences and code, and as-built equipment drawings. Thereafter, an equipment manufacturer develops and tests new code, which a technician subsequently installs into existing switchgear components. Depending on the scope and complexity of the changes, recommissioning of the backup power systems may become necessary.

Capacity Increase

Some power control systems are preconfigured for adding additional capacity. For instance, a hospital may have originally provided capability for paralleling six generators, but installed only four when the system was constructed. In these situations, adding capacity can be a straightforward process provided that sufficient space remains available for new generator sections in the equipment lineup.

If the power control system was not originally designed for expansion, there still may be opportunity to add capacity. This requires careful consideration of the existing design, including the ampacity of the main bus and the short circuit rating of the system. It also requires a thorough understanding of compatibility between existing and new control components. Each of these issues can be best evaluated by contacting a qualified equipment manufacturer or a qualified power system engineer.


Upgrade options for power control systems and paralleling switchgear include direct component upgrades, door-and-panel replacements, control segregation, and software program upgrades. Using one or more of these approaches can enable a facility to improve reliability and maintainability while expanding functionality and capacity. For more information, review the ASCO document entitled Modernizing Existing Power Control Systems or contact an ASCO Power Technologies Representative.

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