Vertiv VA4N21A2 Monitored Rack Transfer Switch PDU — 20A 120V Horizontal

Overview

The Vertiv VA4N21A2 is a 20A, 120V single-phase monitored rack PDU designed for horizontal 0U rack deployment. Purpose-built for data center and IT closet environments where administrators need real-time visibility into current, voltage, and power consumption at the unit level — without stepping up to full outlet-switching hardware. Ten NEMA 5-20R receptacles handle the typical mix of 1U servers, network gear, and storage nodes that populate high-density rows. The VA4N21A2 ships with a NEMA 5-20P plug on a 3-meter (approximately 10-foot) cord, giving enough reach to span horizontal cable management channels in most mid-depth cabinets without an extension.

This PDU sits at the monitored tier of the Vertiv power distribution lineup, meaning you get full environmental telemetry and a rich network management stack — SNMP v1/v2c/v3, HTTPS, SSH, Modbus TCP — without paying for per-outlet switching you may not need. If your load management strategy is handled upstream at the breaker or UPS level, the VA4N21A2 delivers exactly the right feature density for the price point.

Key Features

• Unit-Level Current, Voltage, and Power Monitoring: The onboard LCD and network interface report all three metrics simultaneously. For a 20A/120V circuit supplying a rack of 1U compute, this is the difference between knowing you have 3A of headroom and guessing — critical when adding hardware to a partially loaded row.
• Ten NEMA 5-20R Outlets: A 20A circuit feeding ten 5-20R receptacles matches the standard North American server power cord (C13 to 5-20P) without requiring adapters. At a maximum draw of 16A continuous (80% NEC derate on a 20A branch), you have roughly 1.6A average budget per outlet across a fully loaded unit — plan density accordingly.
• SNMP v1/v2c/v3 with HTTPS and SSH: The VA4N21A2 integrates into any standards-based DCIM or NMS platform that can poll SNMP. v3 adds authentication and encryption, which matters in environments running RADIUS or TACACS+ for centralized access control — both are natively supported. No proprietary agent required.
• RADIUS and TACACS+ Authentication: Centralized credential management means PDU access follows the same IAM policies as your switches and out-of-band management gear. Audit trails land in the same SIEM. This is the spec that separates an enterprise-class PDU from a basic metered strip in a shared-access rack environment.
• LDAP Integration: Directory-based role assignment lets you grant read-only monitoring access to NOC staff and full administrative access to data center engineers without managing local accounts on every PDU individually.
• IPv4/IPv6 Dual Stack: Native IPv6 support means the VA4N21A2 fits into any modern network segment without NAT workarounds — relevant in environments transitioning their management plane to IPv6 ahead of broader network refreshes.
• SMTP and Syslog Alerting: Threshold-based email alerts and syslog forwarding let you route power anomalies directly into your ticketing system or log aggregator. Define a current ceiling for the circuit and get notified before a breaker trips — not after.
• Horizontal 0U Mounting: The horizontal form factor installs in a 1U slot without consuming rack unit space from your compute budget, or mounts to the inside of the rack frame using standard toolless brackets. The black finish blends with most vendor cabinets.
• NTP Time Synchronization: Timestamped event logs are only useful if the clock is accurate. NTP sync ensures power events correlate correctly with application logs and UPS alarms across the facility.
• Modbus TCP Support: Modbus TCP extends integration beyond traditional IT management tools to building management systems (BMS) and SCADA platforms — relevant in mixed IT/OT environments like manufacturing floors or edge compute deployments adjacent to industrial control systems.

Integration and Compatibility

The VA4N21A2 connects to standard rack power distribution management ecosystems via its RJ-45 Ethernet port. The protocol stack — SNMP v3, HTTPS, SSH, SMTP, Syslog, NTP, DHCP, and Modbus TCP — covers the full range of DCIM platforms, including those used in co-location, enterprise, and edge environments. The single RJ-45 serial port supports out-of-band console access for initial configuration or recovery without network connectivity. The USB port provides local management and firmware update capability. Review your UPS and power infrastructure topology before deploying: the 20A/120V rating assumes a dedicated 20A branch circuit — do not share this circuit with other 20A-rated loads. For facilities running 208V or higher input, see the broader Vertiv Geist RPDU family for the appropriate voltage variant. If per-outlet switching and reboot capability are required, evaluate the switched tier of the same product line rather than the VA4N21A2's monitored-only architecture. Consult a power planning guide to size branch circuits and determine whether unit-level or outlet-level monitoring is the right fit for your cabinet density.

Frequently Asked Questions

Q: What is the maximum load the VA4N21A2 can handle continuously?

A: The VA4N21A2 is rated at 20A input (NEMA 5-20P). Per NEC 80% continuous load rule, the safe sustained draw is 16A — approximately 1.9kW at 120V. Plan rack density so aggregate outlet load stays at or below this threshold.

Q: Does the VA4N21A2 support per-outlet power switching or remote reboot?

A: No. The VA4N21A2 is a monitored PDU, not a switched PDU. It provides real-time current, voltage, and power monitoring and alerting, but does not offer per-outlet on/off or remote reboot capability. If outlet-level switching is required, evaluate the switched tier of the Vertiv Geist RPDU line.

Q: What authentication protocols does the VA4N21A2 support for network management access?

A: The VA4N21A2 supports RADIUS, TACACS+, and LDAP for centralized authentication and role-based access control, in addition to local accounts. SNMP v3 provides authenticated and encrypted SNMP polling.

Q: How is the VA4N21A2 mounted in a rack?

A: The VA4N21A2 is a horizontal 0U design, meaning it installs in a 1U rack slot or mounts to the interior of a rack frame without consuming compute rack units. It does not support vertical 0U side-rail mounting.

Q: What input cord and plug does the VA4N21A2 use, and how long is it?

A: The VA4N21A2 ships with a 3-meter (approximately 10-foot) cord terminated in a NEMA 5-20P plug, compatible with standard 20A branch circuit outlets found in most North American data centers and IT closets.

Q: Can the VA4N21A2 integrate with building management systems or industrial control platforms?

A: Yes. The VA4N21A2 supports Modbus TCP, which enables integration with BMS and SCADA platforms beyond traditional IT DCIM tools — making it viable in edge compute or mixed IT/OT environments.