Monitoring relays are the panel's paranoia, made installable: they watch a supply or a load for the conditions that precede damage — phase loss, wrong sequence, over- or under-voltage, current out of window — and trip a contact before the damage is news. Schneider's Harmony range covers the duty in two recognizable shapes: the RMNF22TB30-class three-phase supervisor with NFC phone setup, and the RM35JA32MW-class modular single-phase current relay. They are not competitors; they watch different worlds.
The three-phase supervisor: RMNF22TB30
This unit watches a three-phase supply the way a doctor watches vitals: all phases present, correct sequence, voltage inside windows, asymmetry within limits. Eight amperes of output contact, 208–480 V measurement range, and — the modern part — NFC configuration from a phone: thresholds and timings set from an app instead of a screwdriver and a datasheet. Pump panels, conveyor feeders and anywhere a lost phase quietly cooks a motor are its home ground.
The current-window watch: RM35JA32MW
The single-phase current relay watches a load's consumption instead: current above the window (jam, overload) or below it (dry run, belt loss, open circuit) trips the contact. It is the load's behavioral monitor — the device that knows a running motor drawing zero amps is not running. Pumps, heaters and fans with failure signatures that appear in current are its patients.
The decision rule
Supply health → three-phase supervisor; load behavior → current window. Panels commonly run both: the supply relay guards the feed, the current relay guards each critical load, and the panel's PLC collects their contacts into the alarm narrative.
Why is NFC setup more than a gimmick?
Because repeatability is the game: pre-configured settings cloned across fifty panels by phone beat fifty screwdriver-and-datasheet sessions with fifty chances for a typo. The NFC relay makes panel standardization practical, not aspirational.
Can one current relay protect a three-phase motor?
Only by watching one phase through a CT — it sees that phase's current, not the imbalance. Three-phase protection wants the three-phase supervisor or a phase-failure-capable device; single-phase current windows are for single-phase loads or per-phase supervision by design.
