Vertiv VA5N21A1 Horizontal Switched Rack PDU with Transfer Switch and Outlet-Level Monitoring
Overview
The Vertiv VA5N21A1 is a 20A, 120V single-phase horizontal rack power distribution unit that combines switched outlet control with a built-in rack transfer switch — a pairing that eliminates the need for a separate ATS in space-constrained 0U deployments. Designed for data center rows, edge compute cabinets, and high-density lab racks, the VA5N21A1 delivers individual outlet switching, real-time current/voltage/power monitoring, and an enterprise-grade protocol stack from a compact horizontal form factor. If your environment demands per-outlet power cycling without sending a technician to the rack, or you need automatic source failover baked directly into the PDU, this is the unit to evaluate.
Key Features
- Switched + Transfer Switch in a Single Unit: The VA5N21A1 combines monitored, switched PDU functionality with rack transfer switch capability. That means you get remote outlet cycling AND dual-source redundancy without adding a separate ATS appliance — critical in racks where every U counts and power redundancy is non-negotiable.
- Six NEMA 5-20R Outlets at 20A/120V: Six individually controlled NEMA 5-20R receptacles fed from a NEMA L5-20P locking input plug. At 1.9 kW total capacity and 100–120V nominal input, this unit is sized for edge and branch deployments running moderate-density compute, networking gear, or security appliances — not a 30A/208V high-density compute row.
- Outlet-Level Monitoring — Current, Voltage, Power: Each outlet's current draw, voltage, and power consumption can be tracked individually, not just at the PDU input. This matters for capacity planning: you can identify which specific load is pushing the branch toward its 20A ceiling before a breaker trips, rather than discovering it after an outage.
- LCD Display for Local Status: The integrated LCD panel gives on-site personnel immediate visibility into load status without requiring a network connection or laptop. Useful during initial commissioning or when the management network is unavailable.
- Enterprise Protocol Stack — SNMP v1/v2c/v3, LDAP, RADIUS, TACACS+: The VA5N21A1 supports a full enterprise security and management protocol suite over its single RJ-45 Ethernet port. SNMP v3 enables encrypted, authenticated polling by your NMS or DCIM platform. LDAP, RADIUS, and TACACS+ integration means PDU access can be governed by your existing AAA infrastructure — no local credential sprawl across dozens of units.
- IPv4/IPv6 Dual-Stack with DHCP, HTTPS, SSH: Management traffic runs over IPv4 or IPv6, and both HTTPS and SSH are supported for encrypted remote access. HTTP can be disabled if your security policy requires encrypted-only management — a practical consideration in PCI-DSS or HIPAA environments.
- SMTP, Syslog, and NTP Integration: Alerting via SMTP (email on threshold breach or outlet fault) plus Syslog export to your SIEM and NTP synchronization for accurate event timestamps. These aren't premium add-ons — they're standard on the VA5N21A1, making it straightforward to fold into an existing NOC monitoring workflow.
- Modbus TCP Support: Modbus TCP enables integration with building management systems (BMS) and industrial automation controllers, extending PDU monitoring into broader facility infrastructure — relevant for co-location operators and facilities teams managing power at the room or floor level, not just the rack.
- USB + Serial (RS-232) Console Ports: One USB port and one RS-232 serial port provide out-of-band management access paths. The serial port is particularly useful for initial configuration or recovery scenarios where the network interface is misconfigured or unreachable.
- Horizontal 0U Mounting, 3m Power Cord: The horizontal mounting orientation and 3-meter (approximately 9.8 ft) input cord give you flexibility in where the unit mounts within the rack and how far it can reach to a floor PDU or wall receptacle. The 0U rack footprint means it installs in the mounting channel without consuming any device U-space.
- LED Indicators for At-a-Glance Status: Status LEDs supplement the LCD panel for fast visual triage when walking a data center floor — outlet state and alarm conditions visible without navigating menus.
Integration and Compatibility
The VA5N21A1 integrates with Vertiv power management and monitoring tools and is compatible with third-party DCIM platforms that support SNMP v1/v2c/v3 or Modbus TCP. The dual AAA protocol support (LDAP, RADIUS, TACACS+) allows the unit to slot into enterprise identity management environments without requiring a standalone local user database. For teams managing a mixed fleet of rack PDUs across a DCIM platform, the unit's SNMP MIB can be imported for consistent polling. The SMTP alerting and Syslog output integrate directly with most NOC toolchains. Review your power distribution planning requirements — particularly whether you need a 20A/120V single-phase circuit or require a 208V or 30A variant — before ordering. The NEMA L5-20P input plug requires a matching 20A/120V locking receptacle at the source; confirm your cabinet's whip or floor PDU output before deploying.
Frequently Asked Questions
Q: What is the difference between the monitored and switched functions on the VA5N21A1?
A: The monitored function provides real-time current, voltage, and power readings at the outlet level, giving you visibility into load distribution. The switched function allows remote power cycling or on/off control of individual NEMA 5-20R outlets — useful for rebooting hung devices without a site visit. The VA5N21A1 includes both capabilities plus a rack transfer switch function for dual-source redundancy.
Q: What input plug does the VA5N21A1 use, and what circuit does it require?
A: The VA5N21A1 uses a NEMA L5-20P locking plug and requires a 20A, 120V (100–120V nominal) single-phase circuit. The unit accepts 50 or 60 Hz input frequency. Confirm your cabinet or floor PDU has a matching NEMA L5-20R receptacle before ordering.
Q: Which network management protocols does the VA5N21A1 support?
A: The VA5N21A1 supports SNMP v1, v2c, and v3; HTTPS and SSH for encrypted management access; DHCP, NTP, SMTP, Syslog, LDAP, RADIUS, TACACS+, Modbus TCP, RSTP, and both IPv4 and IPv6. This covers integration with most enterprise NMS, DCIM, and AAA platforms without additional hardware.
Q: Can the VA5N21A1 be managed out-of-band if the Ethernet port is unreachable?
A: Yes. The unit includes a USB port and a serial (RS-232) port for out-of-band console access — useful for initial configuration or recovery when the network management interface is misconfigured or the management VLAN is unavailable.
Q: What is the total power capacity of the VA5N21A1?
A: The VA5N21A1 is rated at 20A input with a maximum load of 1.9 kW at 120V. It distributes this across six NEMA 5-20R outlets. Per standard de-rating practice, plan for a maximum continuous load of approximately 16A (80% of the 20A breaker rating) to avoid nuisance tripping.
Q: Does the VA5N21A1 mount horizontally or vertically?
A: The VA5N21A1 is designed for horizontal mounting in standard EIA/IEC 19-inch rack cabinets. It occupies zero U-space in the device mounting area (0U form factor), installing in the rack's horizontal cable management or mounting channel rather than taking up rack units.
The VA5N21A1 sits at an interesting intersection in the rack PDU market: it's the unit you reach for when a basic monitored PDU isn't enough (you need switching) but you also need to solve for power redundancy in the same rack footprint without bolting on a separate ATS. The NEMA L5-20P / 6-outlet NEMA 5-20R configuration at 1.9 kW puts it squarely in the edge compute, branch office server closet, and mid-density co-lo cage bracket — not a hyperscale row.
Technical Highlights:
- Dual-Mode PDU + Transfer Switch: Combining switched outlet control and rack-level transfer switch in one horizontal 0U unit eliminates a separate appliance, saving rack space and reducing cable runs to two power sources instead of four.
- SNMP v3 + LDAP/RADIUS/TACACS+: The full AAA stack means this unit can authenticate against Active Directory or a RADIUS server — no shared local passwords to rotate across a fleet of PDUs. SNMP v3 with encryption is a hard requirement in many compliance frameworks; it's present here by default.
- Outlet-Level Current/Voltage/Power Monitoring: Granular per-outlet telemetry over a single RJ-45 Ethernet port. For DCIM platforms polling via SNMP, this delivers the resolution needed to spot load imbalances before they become incidents — not just total-unit current.
Deployment Considerations:
- The NEMA L5-20P input is a locking plug — verify your cabinet's power whip or floor PDU has a matching L5-20R receptacle. Swapping to a standard 5-20R source requires an adapter that introduces a potential failure point; plan the source circuit correctly from the start.
- At 1.9 kW / 20A, the VA5N21A1 is appropriate for moderate-density loads. Apply the 80% de-rating rule: plan for no more than ~16A continuous across all six outlets. If your target rack exceeds that, evaluate a higher-amperage Vertiv variant before committing.
This unit is the right call for a branch office or co-location cage deployment where you need remote outlet reboot capability, dual-source failover, and DCIM-compatible telemetry — all without consuming a single rack unit of device space.
