Monitoring Relay Cross-Reference: Zelio RM vs ABB CM Replacement

What is a monitoring relay cross-reference? A cross-reference matches a monitoring relay from one manufacturer's catalog — for example Schneider Electric Zelio Control RM17TE — to the functionally equivalent unit in another range, such as an ABB CM-MPS, based on measured quantity, threshold range, output contact arrangement and mounting width, not part number. Get the auxiliary-supply requirement or output logic wrong and a "drop-in" replacement doesn't wire the same way the old relay did, or leaves the panel without fail-safe protection on a lost supply. This guide covers how function-based matching works, how Zelio Control RM17, RM22 and RM35 map to the ABB CM range across phase, voltage, current, level and temperature monitoring, what to check on the terminal block before swapping, and where the two ranges genuinely diverge.

Why a Part Number Never Tells the Whole Story

An RM17TE and a CM-MPS both watch a three-phase supply. Neither number tells you that on its own. The catalog code encodes the manufacturer's internal range logic — RM17 is Schneider's single-function tier, CM-MPS sits in ABB's three-phase monitor family — and two codes that look similar can cover different functions, while two very different-looking codes can do the same job.

What we see in the field: panel builders sometimes order "the same relay, different brand" from a distributor list without checking the actual function set, and end up with a phase-sequence relay where they needed a voltage-window relay. The fix is to match on function first, part number second.

Match by Function, Not by Catalog Code

Four parameters decide whether two monitoring relays are interchangeable:

Measured quantity — phase sequence/loss, voltage, current, level, or temperature. Threshold range and adjustability — a fixed-threshold relay is not a substitute for one with an adjustable window. Output contact arrangement — one change-over contact (SPDT) versus two (DPDT) changes how many circuits the relay can drive directly. Auxiliary supply requirement — some three-phase monitors draw power straight from the measured lines and need no separate 24V or 230V feed; others don't.

Miss the auxiliary-supply column and the replacement relay sits dead in the panel until someone runs a new feed to it.

Three-Phase Supply and Phase-Sequence Relays: RM17TE vs CM-MPS / CM-MPN

Schneider's RM17TE checks phase sequence, phase loss, asymmetry and over/undervoltage on a three-phase supply in one module. ABB's CM-MPS covers the same function set and, like the RM17TE, needs no separate auxiliary supply on most variants — it self-powers from the monitored lines. CM-MPN is the ABB variant built for supplies that do need an aux feed. For a deeper look at how these relays work, see the phase sequence and phase failure relay article.

Wrong rotation on a motor means it runs backwards. Both ranges block the start until sequence is correct — that part of the function is not brand-specific, it is the reason this relay class exists.

Voltage and Current Monitoring: RM17UB / RM35UA vs CM-ESS / CM-EFS

Single-phase voltage monitoring on the Schneider side runs from the compact RM17UB up to the multifunction RM35UA, both with adjustable over/undervoltage thresholds and hysteresis. ABB's single-phase current monitoring sits in the CM-ESS and CM-EFS lines; ABB's voltage monitoring is covered within the broader CM range rather than a single dedicated code, so the cross-reference has to go by function set, not a 1:1 code mapping. Before committing to a substitute, walk through the how to select a phase and voltage monitoring relay checklist — it uses the same four parameters as this guide.

Current monitoring splits the same way: undercurrent catches a broken belt, a dry-running pump, or a lost load; overcurrent catches a jam. RM35JA on the Schneider side and CM-EFS on the ABB side both do this via a built-in shunt or an external CT depending on the current range.

Level and Temperature Monitoring: RM35LV vs CM-ENS / CM-ENE, RM35ATR vs CM-TCS / CM-MSS

Level relays on both sides use conductive sensing — electrodes measure liquid presence between probes, with sensitivity in kOhm adjustable for the liquid's conductivity. RM35LV, with a positive-safety variant for dry-run-critical applications, maps functionally to ABB's CM-ENS/CM-ENE pair.

Temperature is where the standard matters more than the brand. A PTC thermistor relay — RM35ATR on the Schneider side, CM-TCS or CM-MSS on the ABB side — trips when the sensor embedded in the motor winding reaches its reference resistance per IEC 60947-8, roughly 3.3 kOhm. A PT100/PT1000 relay instead reads an actual temperature value and switches at a set point; the two sensor types are not interchangeable even within one brand's range. See the monitoring relay engineering guide for the full breakdown of sensing types.

Hysteresis and Threshold: Getting the Setting Right When You Switch Brands

Hysteresis is the reset band around the trip threshold, and it's the setting that most often gets copied wrong across a cross-reference. If the old relay's hysteresis was expressed as a percentage of the threshold and the new one uses an absolute value, or the reverse, a setting that looks identical on paper produces a different reset point in practice.

Trip delay is the other setting worth re-checking: a brief supply dip that the old relay rode through on a 2-second delay will nuisance-trip on a replacement set to 0.5 seconds, even though the threshold is identical. Walk through both settings using the how to set a voltage monitoring relay guide before commissioning.

What to Check Before You Swap the Relay

Terminal layout first — module width (17.5 or 22.5 mm typically) and terminal position rarely match across brands even when the DIN-rail footprint does, so re-wiring is normal, not a sign something's wrong. Output contact count next: a relay with one change-over contact can't directly replace one wired for two independent circuits without adding an auxiliary contactor.

Output logic is the one that gets missed most: normally-energized (fail-safe, de-energizes on fault or on loss of the auxiliary supply) versus normally-de-energized wiring changes what happens to the downstream contactor or PLC input if the relay itself loses power. Confirm automatic versus manual (latched) reset too — a latched relay needs a manual reset action after every trip, which some retrofits don't account for.

The output contact from either range drives a contactor coil, a PLC input, or an alarm circuit rather than switching the load itself, so check the downstream contactors coil rating against the relay's contact rating on both the old and new part.

Conclusion

A monitoring relay cross-reference works when it matches function, not catalog code: measured quantity, threshold range, output contact count, output logic and auxiliary-supply requirement. Schneider Zelio Control and ABB CM cover the same core functions — three-phase supply, voltage, current, level, temperature — with different module widths, terminal layouts and, on some models, different auxiliary-supply needs. Confirm those five parameters before ordering a substitute, recheck hysteresis and trip delay on commissioning, and treat the physical rewiring as routine rather than a sign of a bad match. Browse the full monitoring and control relays range to compare current stock across both brands.