| PDU Type | Determine the level of monitoring, control, and redundancy required. | - Basic: power distribution only
- Metered: local current or power readings
- Monitored: networked input and outlet measurements
- Switched: remote outlet control plus monitoring
| Networked models require suitable Ethernet connectivity, IP addressing, and management-system support. | Use a basic unit for simple distribution; choose monitored or switched models when visibility and remote control are operational priorities. |
| Input Voltage | Match the PDU input rating with the facility supply and rack power architecture. | - Single-phase systems commonly use approximately 100–240 V AC
- Three-phase systems commonly use approximately 208–415 V AC, depending on the electrical system
| Voltage, phase arrangement, and frequency must match the upstream circuit and the PDU nameplate rating. | Confirm the actual measured or documented supply voltage before ordering. Do not rely solely on nominal regional standards. |
| Phase Configuration | Assess whether the rack is supplied by single-phase or three-phase power. | - Single-phase: suitable for many low- and medium-density racks
- Three-phase: supports higher rack capacity and improved power distribution
| Three-phase PDUs may use different input connectors and require compatible upstream protection and installation procedures. | Select three-phase distribution when rack density, available capacity, or space efficiency justifies it. |
| Rated Current | Compare the PDU current rating with the circuit breaker rating and expected operating load. | - Typical rack PDU ratings include 10 A, 16 A, 20 A, 24 A, 30 A, and higher
- Actual usable capacity depends on local electrical rules and continuous-load limits
| The PDU rating must not exceed the capacity of the upstream circuit, connector, cable, or facility distribution equipment. | Size for normal operating demand with reserve capacity. Avoid operating continuously at the maximum nameplate rating. |
| Power Capacity | Calculate the required real power for all connected equipment. | - Single-phase apparent power: VA = V × A
- Three-phase apparent power: VA ≈ √3 × V × A
- Real power: W = VA × power factor
| Power factor, load balance, ambient conditions, and applicable derating can reduce practical capacity. | Use measured load data where possible and include planned equipment growth rather than sizing only for the present load. |
| Continuous Load and Headroom | Allow operating margin between expected load and the maximum permitted circuit capacity. | A commonly used design approach is to keep continuous demand at or below approximately 80% of the branch-circuit rating, subject to local electrical codes. | Some jurisdictions and installations may apply different requirements. The circuit breaker, conductor, connector, and PDU must be assessed together. | Plan for at least 20% practical capacity reserve unless the applicable code or engineering design specifies otherwise. |
| Outlet Configuration | Match outlet quantity, type, and location to the equipment power supplies. | - IEC 60320 C13: commonly used for standard server and network equipment cords
- IEC 60320 C19: used for higher-current equipment connections
- Mixed C13/C19 layouts are common in higher-density racks
| Check plug type, voltage rating, current rating, cord length, and clearance between adjacent outlets. | Count existing and planned devices, then reserve spare outlets for maintenance and future expansion. |
| Input Connector | Verify that the PDU plug or hardwired input method matches the facility receptacle or installation plan. | Common connector families include IEC 60309 industrial plugs and IEC 60320 appliance couplers, with ratings varying by voltage, phase, and current. | Connector shape alone is insufficient; voltage, pole configuration, grounding, current rating, and keying must all be compatible. | Confirm the exact connector specification with the electrical contractor before purchase or installation. |
| Frequency | Check whether the PDU and connected equipment support the facility frequency. | Common systems operate at 50 Hz or 60 Hz; some equipment supports both. | The PDU, upstream supply, and connected equipment should have compatible frequency ratings. | Choose a dual-frequency model only when its nameplate and technical documentation explicitly support the required range. |
| Voltage Compatibility of Loads | Review the input range of every server, storage system, switch, and auxiliary device. | Many modern IT power supplies accept a broad range such as 100–240 V AC, but not every device has universal input capability. | A PDU distributes the supplied voltage; it does not convert voltage unless it is specifically designed as a transformer-based system. | Verify equipment power-supply labels and documentation before connecting loads to a different voltage system. |
| Phase and Circuit Balance | For multi-phase PDUs, distribute loads evenly across phases. | Balanced loading reduces neutral-current stress and improves available capacity across the electrical system. | Equipment with single-cord inputs may not automatically balance itself across phases. | Use outlet-level or phase-level metering and document the intended connection plan for each rack. |
| Redundant Power Feeds | Determine whether equipment has dual power supplies and whether separate power paths are available. | - A/B distribution: each equipment power supply connects to a different PDU or upstream circuit
- Single-feed distribution: one PDU supplies the equipment
| Redundancy is effective only when the two feeds originate from genuinely independent circuits or power paths. | For critical equipment, use separately protected A and B feeds and verify that each feed can support the required load. |
| Monitoring Requirements | Identify the level at which power data must be measured. | - Input-level monitoring
- Phase-level monitoring
- Outlet-level monitoring
- Environmental sensor support
| More detailed measurement may require additional network configuration, sensors, or software integration. | Use outlet-level monitoring when capacity planning, chargeback, troubleshooting, or device-level energy analysis is required. |
| Remote Switching | Assess whether outlets need remote reboot, sequencing, or scheduled control. | Switched PDUs can provide outlet-level on/off control, delayed power-up, and grouped outlet operations. | Remote switching can interrupt equipment unexpectedly and should be protected by role-based access and operational procedures. | Use switching only where remote recovery or controlled startup provides a clear operational benefit. |
| Physical Installation | Check rack height, mounting orientation, cable routing, and available clearance. | Common formats include vertical 0U installation and horizontal rack-mount installation, including 1U and 2U designs. | Confirm rack depth, vertical mounting spaces, plug clearance, airflow paths, and access to circuit breakers or displays. | Choose vertical installation for maximum outlet density when compatible mounting space is available. |
| Environmental Conditions | Review operating temperature, humidity, altitude, and airflow conditions. | Typical data-centre environments are temperature- and humidity-controlled, but the exact allowable range is product-specific. | High temperature, restricted airflow, dust, or elevated altitude may require derating or a different enclosure specification. | Compare the PDU environmental rating with the rack location and the facility operating envelope. |
| Safety and Certification | Verify electrical safety approvals, grounding, overcurrent protection, and installation requirements. | Look for documentation showing compliance with applicable national and international safety standards, such as IEC or equivalent local requirements. | Certification requirements vary by country, voltage system, installation method, and facility policy. | Use only equipment approved for the installation jurisdiction and have fixed electrical work completed by qualified personnel. |
| Future Expansion | Estimate additional servers, storage, networking devices, and higher-density hardware expected during the service life. | A practical expansion allowance may include spare outlets, unused circuit capacity, and additional monitoring points. | Expansion must remain within the limits of the upstream electrical infrastructure, not just the PDU outlet count. | Balance expansion capacity against efficiency and cost; excessive oversizing can reduce utilization and increase capital cost. |
