{"schemaVersion":1,"slug":"residual-current-monitor","name":"Residual current monitor","kind":"symbol","abbreviation":"RCM","aliases":["RCM","earth leakage monitor","residual current monitoring device"],"category":"measurement-protection","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"Device with a toroid that measures residual current and gives a warning or signal without interrupting the circuit itself.","description":["A residual current monitor measures residual current with a summation toroid around the circuit conductors and signals when it exceeds a threshold. It is used where an unexpected trip would be unacceptable but rising leakage still needs attention, for example in data centres and process plant.","An RCM does not disconnect the circuit by itself, so it is not a substitute for an RCD where automatic disconnection is required. The symbol shows the toroid and monitor, but the reader must find out whether its output drives an alarm only or a separate switching device."],"readingNotes":["Check whether the output alarms or trips another device.","Confirm that all live conductors, including neutral, pass through the toroid."],"drawingChecklist":["Show toroid and conductors","State threshold","Reference alarm or trip output"],"distinction":"An RCM signals residual current; an RCD measures it and also disconnects the circuit.","facts":[{"label":"Sensing","value":"Summation toroid around live conductors"},{"label":"Action","value":"Signal or alarm, no integral disconnection"},{"label":"Preview","value":"Functional illustration of the device role; not a product footprint or certified standard graphic"}],"references":[{"sourceId":"pub-symbol-rcd-categories","relevance":"Public residual current device categories for comparison with monitoring devices."},{"sourceId":"pub-symbol-earth-fault","relevance":"Public context for residual current measurement."}],"related":["core-balance-current-transformer","earth-fault-current-relay","insulation-monitoring-relay"],"artwork":"s28-residual-current-monitor","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","plainEnglish":{"title":"What does Residual current monitor mean?","introduction":"A residual current monitor measures residual current with a summation toroid around the circuit conductors and signals when it exceeds a threshold. It is used where an unexpected trip would be unacceptable but rising leakage still needs attention, for example in data centres and process plant.","example":"An RCM does not disconnect the circuit by itself, so it is not a substitute for an RCD where automatic disconnection is required. The symbol shows the toroid and monitor, but the reader must find out whether its output drives an alarm only or a separate switching device.","drawings":"Check whether the output alarms or trips another device. Confirm that all live conductors, including neutral, pass through the toroid. An RCM signals residual current; an RCD measures it and also disconnects the circuit.","terms":[{"name":"Terminal","meaning":"An identified point where a conductor connects."},{"name":"Signal","meaning":"Electrical information passed between devices, rather than necessarily the main power supply."},{"name":"Rating","meaning":"A value stating the conditions for which equipment is specified."}],"diagram":"flow","steps":["Identify the device and form","Read the connections and state","Check the equipment reference"],"caption":"A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.","sources":[{"label":"Residual current device categories","url":"https://www.se.com/au/en/faqs/FAQ000218859/"},{"label":"Residual current and neutral-earthing protection context","url":"https://new.abb.com/medium-voltage/digital-substations/campaigns/earth-fault-protection-portfolio/earth-fault-offering"}],"detail":"Device with a toroid that measures residual current and gives a warning or signal without interrupting the circuit itself. An RCM signals residual current; an RCD measures it and also disconnects the circuit.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/residual-current-monitor","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/residual-current-monitor.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pub-symbol-rcd-categories","title":"Residual current device categories","publisher":"Schneider Electric","url":"https://www.se.com/au/en/faqs/FAQ000218859/","type":"manufacturer","scope":"Public manufacturer explanation of the equipment function and selection context.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public residual current device categories for comparison with monitoring devices."},{"id":"pub-symbol-earth-fault","title":"Residual current and neutral-earthing protection context","publisher":"ABB","url":"https://new.abb.com/medium-voltage/digital-substations/campaigns/earth-fault-protection-portfolio/earth-fault-offering","type":"manufacturer","scope":"Public manufacturer explanation of the equipment function and selection context.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public context for residual current measurement."}]}