What the Raritan PX4 measures
Understanding Residual Current Measurement
Data centre reliability depends on detecting electrical faults before they cause damage. When insulation degrades in your facility’s circuits, dangerous current escapes through ground conductors and exposed metal, creating fire risks and equipment damage. Without proper monitoring, these hazards remain invisible until catastrophic failure occurs.
The Raritan PX4 delivers real-time residual current measurement across your power distribution infrastructure, identifying insulation degradation at early stages. By continuously monitoring current leakage to ground, the PX4 enables you to address faults proactively and comply with electrical safety standards, protecting both your equipment and facility.
In a healthy circuit, current flows in the phase and neutral conductors only. When insulation degrades, some of that current escapes via the ground conductor. It travels through exposed metal, through cable shielding, through whatever path leads to earth. That is residual current.
At low levels it is invisible. At higher levels it trips protection devices, damages equipment, and creates fire risk. Most metered PDUs have no sensor for it.
Residual current is any current that flows outside the intended phase-neutral circuit path, typically via the ground conductor as a result of insulation degradation or a ground fault. IEC 62020 defines the thresholds and testing requirements for residual current monitors. A residual current monitor (RCM) measures this leakage continuously and triggers an alarm when it exceeds a configured limit.
What the Raritan PX4 measures
The PX4 embeds RCM sensors in the inlet section. Two sensor types cover different leakage scenarios.
- [1]Type A: AC leakage detection down to 6 mA, across all lines (1-phase or 3-phase) — build-to-order option M5
- [2]Type B Single Channel: AC and DC leakage, 15–300 mA range, all lines — build-to-order option M11 (PX4 M27)
- [3]Type B Three Channel: AC and DC leakage per phase, 3-phase units — build-to-order option M18 (PX4 M28)
- [4]Patented automated self-test: 15 mA injected through sensor on a schedule — no electrician, no downtime
- [5]EN50600 2-2 compliant: embedded neutral current metering accurate to 1%
When a threshold is crossed, the PDU activates a local alarm, raises an alert in firmware, and sends configurable notifications via email, SMS, or SNMP trap. Thresholds are set through the PDU firmware and can feed into DCIM software or a building management system via MODBUS.
The audit question most metered PDUs cannot answer
Safety audits for colocation operators, government facilities, and critical infrastructure typically include this question: how does your organisation detect insulation faults in live racks?
A standard metered PDU measures current on the phase and neutral conductors. It has no sensor for current that escapes via the ground path. Residual current from a degrading server PSU or a mis-wired connection falls entirely outside its measurement window.
For colocation operators, a residual current event that trips protection devices means customer downtime and SLA exposure. For government and critical facilities, leakage current above safety thresholds can constitute a compliance failure. EN50600 2-2 requires neutral conductor monitoring. Raritan PDUs with RCM meet that requirement.
RCM is a build-to-order option on Raritan PX4 models. If your rack infrastructure is already Raritan, adding this capability does not require a separate appliance or additional wiring.
Frequently asked questions
Residual current monitoring (RCM) is a capability embedded in intelligent PDUs that continuously measures any current flowing via the ground conductor rather than through the intended phase and neutral path. This residual current indicates insulation degradation or a ground fault. The Raritan PX4 embeds RCM sensors at the inlet and triggers configurable alerts via email, SMS, or SNMP trap when leakage exceeds a set threshold.
Raritan PX4 offers two RCM sensor options. Type A detects AC leakage current down to 6 mA across all lines in single-phase or three-phase PDUs. Type B detects both AC and DC leakage current in the 15–300 mA range per IEC 62020, with a single-channel option covering all lines and a three-channel option monitoring each phase separately in three-phase deployments.
IEC 62020 is the international standard for residual current monitors. It defines the residual operating current threshold above which an alarm must be triggered and specifies testing accuracy requirements. EN50600 2-2, the European data centre infrastructure standard, includes neutral conductor monitoring as a requirement. Raritan PDUs with RCM are EN50600 2-2 compliant and include embedded neutral current metering accurate to 1%.
A standard metered PDU measures total current draw, voltage, and power consumption on the phase and neutral conductors. It has no sensor for current that escapes via the ground path. Residual current resulting from insulation degradation flows outside the measurement window of a basic PDU, so it goes undetected until a protection device trips or visible damage occurs.
Raritan RCM sensors include a patented automated self-test function. The PDU injects a 15 mA test current through the RCM sensor on a schedule configured by the operator. If the sensor responds correctly, it returns to normal monitoring. If the sensor fails the test, the PDU raises a sensor fault alert. This eliminates the need for periodic manual testing by an electrician and removes associated downtime.
Colocation operators, government facilities, healthcare data centres, and critical infrastructure operators are the environments where RCM is most commonly required. For colocation, a residual current event that trips protection devices causes customer downtime and SLA exposure. For government and critical facilities, leakage current above safety thresholds can constitute a compliance failure under health and safety regulations or data centre design standards such as EN50600.
Enova Technologies is an authorised Raritan reseller in Singapore. Contact us to discuss RCM options for your rack PDU deployment.
Ask us about Raritan RCM
Published by
eNOVA Technologies is Singapore's specialist distributor for data centre IT management solutions, representing Adder, Guntermann & Drunck, Raritan, Sunbird, ZPE Systems, and VuWall across Singapore and Southeast Asia. Our technical content is produced with AI assistance and reviewed by our in-house team before publication.
This article was produced with AI assistance and reviewed by the eNOVA Technologies team. All technical claims are verified against manufacturer documentation.
