N+1 redundancy in a data center power system means providing the capacity required to support the critical load—represented by N—plus one additional capacity component. The additional component gives the facility another source of available capacity when equipment is being serviced or when the power system is operating with one component unavailable.
N+1 configurations can be used with UPS systems, generators and other critical-power equipment. For facilities building, expanding or upgrading power infrastructure, Critical Infrastructure Group can help source UPS systems, commercial and industrial generators and supporting equipment for redundant data center power configurations.
What Does the “N” Mean in N+1?
In an N+1 configuration, N represents the amount of equipment required to support the intended load.
For example, if three UPS modules are required to support the critical load, those three modules represent N. Adding a fourth compatible module provides the additional capacity component represented by +1.
The same concept can be applied to generator plants and other capacity systems. If the required load can be supported by a defined number of generators, an additional generator may be incorporated to provide N+1 capacity.
The exact configuration depends on equipment size, system architecture and the data center’s operating requirements. CI Group can help customers identify available equipment once those capacity and electrical requirements have been established.
Why Do Data Centers Use N+1 Redundancy?
N+1 gives a data center additional flexibility in how critical-power capacity is provided.
Instead of installing only the exact amount of equipment needed for the connected load, the system includes an additional capacity component. That additional equipment can support a power strategy designed around equipment servicing, system upgrades and overall availability.
Uptime Institute identifies redundant capacity components as an important part of data center infrastructure planning. Its Tier Classification System progresses from basic capacity to redundant capacity, concurrent maintainability and fault tolerance depending on the facility’s business and availability objectives.
Review Uptime Institute’s Data Center Tier Classification System.
How Does N+1 Apply to UPS Systems?
UPS systems can be configured in several ways to provide additional capacity. Depending on the equipment, an N+1 arrangement may use multiple UPS modules within a modular system or multiple UPS systems configured to support the required load.
The U.S. Department of Energy discusses N+1 UPS configurations in its data center design guidance and notes that the number and size of UPS units are important considerations when planning both redundancy and operating efficiency.
Review the U.S. Department of Energy’s Best Practices Guide for Energy-Efficient Data Center Design.
When selecting a new UPS configuration, operators can consider current load, future capacity requirements and the desired redundancy arrangement together.
For more on determining the required system capacity, see What Size UPS Does a Data Center Need?
CI Group offers UPS equipment across a broad range of sizes, including 1201+kVA UPS systems for large data center and mission-critical applications.
How Does N+1 Apply to Backup Generators?
The same capacity concept can be incorporated into a data center generator plant.
If the facility requires a certain number of generator sets to support its designated critical load, additional generator capacity can be included as part of the redundancy strategy.
This is especially relevant for larger facilities where several generator sets may operate together. The project team can establish the required critical load, individual generator capacity, electrical configuration and desired redundancy before equipment is selected.
CI Group supplies generators across a wide range of capacities, including 2001+kW generator systems for large-scale data center and critical-infrastructure projects.
For generator-specific planning, see How Do You Size a Backup Generator for a Data Center?
N+1 Is One Part of the Complete Power Architecture
Redundant capacity works together with the rest of the data center’s electrical infrastructure. UPS systems, generators, transfer equipment and distribution paths all contribute to how power reaches the critical load.
Uptime Institute notes that equipment count by itself does not establish a particular Tier classification. The way capacity components are connected to distribution paths and the way the overall infrastructure operates are also important.
For that reason, a data center can use N+1 equipment as one part of a broader critical-power strategy tailored to its availability requirements.
CI Group’s resource Distributed Redundancy: Maximum Availability at Minimal Cost provides additional information about redundancy approaches for critical-power systems.
Redundant Capacity Can Also Support Planned Maintenance
One of the practical advantages of additional capacity is the ability to plan maintenance around the equipment supporting the critical load.
UPS systems, batteries, generators and supporting electrical equipment all require periodic service. A power architecture with appropriately planned redundant capacity can provide greater flexibility when maintenance or equipment replacement is scheduled.
CI Group provides UPS Maintenance Services and UPS Preventative Maintenance & Inspection for data centers and other mission-critical facilities.
See How Often Should a Data Center UPS Be Maintained? for additional maintenance planning information.
Planning an N+1 Data Center Power Configuration
Before sourcing equipment for an N+1 configuration, the project team should establish:
- The critical load the system must support
- Required UPS capacity in kW and kVA
- Generator capacity required for the designated critical load
- The number and size of capacity components
- Required voltage and electrical configuration
- Battery runtime requirements
- Planned data center expansion
- Maintenance and replacement requirements
- Available space for additional equipment
- The overall power-distribution architecture
With those requirements defined, equipment can be matched to both the present load and the facility’s longer-term power strategy.
Build Redundant Capacity Into Your Data Center Power Plan
N+1 redundancy gives data center operators a practical way to add capacity beyond the minimum equipment required for the critical load. Whether the project involves UPS systems, generators or a broader critical-power expansion, planning the additional capacity from the beginning makes it easier to select equipment that supports the facility’s operating objectives and future growth.
Critical Infrastructure Group can support these projects with new, surplus and refurbished UPS equipment, large-capacity generators, automatic transfer switches, UPS rentals and related critical-power services through its Data Center Power Infrastructure solutions.
Need Equipment for an N+1 Data Center Power Configuration?
Share your UPS capacity, generator, voltage and project requirements with CI Group. We can help identify available critical-power equipment for new data center construction, expansion and replacement projects.