Schneider Zelio RXM, RSB and RSL Interface Relays Review
What is the Schneider Zelio interface relay range? Zelio covers interface relays in three families — RXM (miniature plug-in, IEC 61810), RSB (interface plug-in relays with integral socket options) and RSL (slim, roughly 6 mm wide) — spanning 24 VDC to 230 VAC coils and 1 to 4 change-over contacts on RXZE and matching sockets. Pick the wrong family and you either burn DIN-rail width you don't have, or pay for socket flexibility a fixed panel design never uses. This review covers coil and contact coverage across RXM, RSB and RSL, socket and accessory differences, where each family fits a PLC panel, and how the range compares against ABB's CR-P/CR-M/CR-U on the same interfacing job.
What Sits Inside the Zelio Range: RXM, RSB and RSL
Zelio is Schneider's control-relay brand, and the interface segment inside it splits by contact count, socket philosophy and DIN-rail footprint rather than by voltage class. RXM is the miniature plug-in line: RXM2 gives 2 CO (DPDT), RXM4 gives 4 CO, and both mount on RXZE sockets with clip-on LED and coil-suppression modules. RSB is built around the socket as much as the relay — several RSB variants ship with an integral or matched socket rather than treating relay and socket as two separately specified parts. RSL is the density play: a slim body around 6 mm wide, meant to sit rail after rail next to a PLC output card where every millimetre of cabinet width counts.
None of the three is a strict upgrade of another. A panel builder standardizing on RXM for general control interfacing will still reach for RSL the moment a 32-point I/O rack needs one relay per point in a cabinet sized for half that. What we see in the field: teams that mix families inside one panel do it deliberately, RXM for the bulk of the interfacing and RSL only where rail space is the binding constraint — not as a random parts-bin choice.
RXM: The Miniature Plug-in Workhorse
RXM is the default choice for general Zelio interfacing — the relay most panels reach for first. RXM2 (2 CO) and RXM4 (4 CO) cover the bulk of PLC-to-load jobs: driving a contactor coil, a solenoid valve, an indicator circuit. Coil options run from 24 VDC through the common AC ratings up to 230 VAC, so the same physical footprint services a DC-logic panel and an AC-control panel without changing socket type.
Socket and Module Ecosystem
RXZE sockets take RXM relays in screw or push-in terminal versions, and the same socket footprint accepts clip-on LED and suppression modules. That modularity is the actual selling point: swap a burned coil without re-wiring the socket, add a freewheel diode module after the fact if a design review flags a DC coil driven straight from a PLC transistor output. Socket rating, not relay rating, sets the ceiling on what you can wire into the terminal — check both when you spec a job, not just the relay's datasheet.
RSB: Interface Plug-in Relays with Integral Sockets
RSB targets a different failure mode: relay and socket bought, stocked and specified as separate line items, then mismatched on-site. Several RSB variants come with the socket built in or pre-matched, so the part number itself defines the terminal type and pinout instead of leaving that to a second purchase order. For a panel shop running through hundreds of interface points a week, that removes one class of wiring error — a relay plugged into the wrong-pinout socket bought from a different line item.
RSB covers 1 CO and 2 CO variants for straightforward interfacing jobs where you don't need RXM's 4 CO density or RSL's width. It sits between RXM's general-purpose flexibility and a purpose-built single-function relay — useful when a bill of materials benefits from fewer distinct socket part numbers, even if it means less mix-and-match flexibility later.
RSL: Slim Relays for High-Density I/O
RSL is where Zelio answers the density question directly. At roughly 6 mm wide, an RSL relay takes about a third the rail space of a standard plug-in body, which matters when a PLC output card has 32 or 64 points and every one needs isolation before it reaches field wiring. Push-in terminal options on RSL speed up wiring on runs where dozens of identical relays go in one after another — a screw terminal re-torqued 40 times on the bench costs real assembly time that push-in avoids.
The trade-off is contact capacity: slim bodies generally carry fewer or lower-rated contacts than RXM's 4 CO ceiling, because there isn't physical room for more contact sets in a 6 mm shell. RSL is a density and speed-of-wiring choice, not a higher-capacity one.
Coil Voltage and Contact Ratings Across the Three Families
All three families share the same coil-voltage logic even though contact counts differ. 24 VDC is the workhorse rating for PLC-driven panels because it matches the PLC's own logic-side supply; 24/48/110/230 VAC options cover control circuits fed from a transformer secondary rather than a DC rail. Contacts are rated separately for AC (commonly 6 A / 250 VAC, AC1) and DC, and DC breaking capacity drops sharply as voltage rises — there's no natural current zero-crossing to help quench the arc, so a DC1-rated contact at 24 V does not scale linearly to 110 VDC.
Formula: Relay coil power draw — Source: IEC 61810, general coil-rating principle
Pcoil = Vcoil × Icoil
| Symbol | Description | Unit |
|---|---|---|
| Pcoil | Coil power consumption | W |
| Vcoil | Rated coil voltage | V |
| Icoil | Coil holding current at rated voltage | A |
Interface relay coils draw a few hundred milliwatts to roughly 1 W — small next to a contactor coil, but not zero when a PLC output card is driving sixteen or thirty-two of them simultaneously. Total coil load across a rack is worth summing before you assume the output card's common current rating has headroom to spare. This is also where relay coil voltage selection and coil suppression choices interact: a DC coil without a freewheel diode clamps nothing when the PLC transistor output switches off, and the collapse spike finds the transistor instead.
RXM vs RSB vs RSL: Which Family for Which Job
The honest answer depends on what the panel is optimizing for — rail space, wiring speed, or BOM simplicity — not on which family is generally superior, because none is.
| Criteria | RXM | RSB | RSL |
|---|---|---|---|
| Contact count | 2 CO or 4 CO | 1 CO or 2 CO | Fewer, lower-density contacts |
| Socket approach | Separate RXZE socket, modular | Integral or pre-matched socket | Slim dedicated socket |
| DIN-rail width | Standard plug-in footprint | Standard footprint | ~6 mm, high density |
| Best fit | General-purpose PLC interfacing | High-volume runs, fewer part numbers | 32+ point I/O racks, tight cabinets |
| Terminal options | Screw or push-in | Screw or push-in (model-dependent) | Push-in common |
A control panel with moderate point count and a preference for field-swappable relays leans RXM. A panel shop running the same interfacing design across many cabinets, where reducing distinct socket SKUs saves real procurement time, leans RSB. A cabinet where the PLC card itself dictates 48 isolated points in a footprint sized for 20 standard relays has one workable answer: RSL. This depends on whether the PLC output sinks or sources current too — check that against the coil polarity before locking the family in, since a sinking-output card and a DC coil wired for a sourcing output will simply never pull in.
Where Zelio Sits Against ABB's CR Range
ABB's interface and control relays answer the same job through CR-P (pluggable, 1-4 CO), CR-M (industrial plug-in, higher current, 2-4 CO) and CR-U (universal range), each on its own CR-series socket with clip-in LED and suppression modules. The two brands cover overlapping ground — miniature and slim plug-in relays, screw and push-in socket options, higher-current power variants — and differ mainly in slim-module width, socket keying and accessory ecosystem rather than in the underlying interfacing principle. Neither brand's slim or miniature line is a drop-in mechanical replacement for the other's socket, so a cross-brand swap means requalifying the socket footprint, not just matching contact ratings.
For teams standardizing a panel design across suppliers, the practical decision usually comes down to what's already stocked and what the existing socket tooling on the shop floor supports — see the interface and coupling relay engineering guide for the full cross-brand breakdown, including Finder, Phoenix Contact and Weidmuller equivalents.
Fitting Zelio Relays Into the Rest of the Panel
An interface relay rarely works alone. It sits between a PLC output and whatever load needs isolating — most often a contactor coil, sometimes a plug-in relay and socket system feeding a second control loop. Getting the family right matters less than getting the basics right around it: matching coil voltage to the driving output, sizing contact rating to the actual load rather than a generic assumption, and fitting suppression on any DC coil driven by solid-state PLC outputs. See how to select an interface relay for PLC outputs for the selection sequence in full. Where the switched load is a motor branch rather than a coil, a thermal overload relay handles the overcurrent protection side — a job the interface relay itself is not rated to do.
Frequently Asked Questions
What's the practical difference between RXM and RSB?
RXM pairs a relay with a separate RXZE socket, so relay and socket are specified and stocked independently and can be mixed across variants. RSB variants come with an integral or pre-matched socket, which cuts the chance of pairing a relay with the wrong socket pinout on high-volume builds.
When does RSL make more sense than RXM?
RSL makes sense when DIN-rail width is the binding constraint — typically a PLC I/O rack with a high point count in a cabinet that wasn't sized for standard-width plug-in relays. RXM remains the better default where rail space isn't tight and 4 CO density or field-swappable sockets matter more.
Do RXM, RSB and RSL all use the same coil voltages?
They share the same range of common coil ratings — 24 VDC plus 24/48/110/230 VAC options — but the specific voltages stocked for a given contact count vary by model. Confirm the exact coil voltage against the part you're ordering rather than assuming full cross-family availability.
Can Zelio RXM relays plug directly into ABB CR-P sockets?
No. Each brand's socket footprint, terminal keying and accessory system is specific to its own relay line. Swapping brands means requalifying the socket, not just matching contact ratings.
Does an RXM relay need a coil-suppression module when driven by a PLC transistor output?
On a DC coil, yes if the output is a transistor rather than a relay-output card — the freewheel diode module clamps the coil's collapse spike when the transistor switches off. Skip it and repeated switching risks the driving transistor.
Which Zelio family suits a panel shop building the same design repeatedly?
RSB's integral-socket models are worth evaluating first, since they reduce the number of distinct socket part numbers on the BOM. Where 4 CO density is needed, RXM remains the wider-coverage option even on repeat builds.
Conclusion
RXM, RSB and RSL are not tiers of the same product — they answer different constraints inside the same interfacing job. RXM covers general-purpose PLC-to-load interfacing with the widest contact and socket flexibility. RSB trades some of that flexibility for fewer part numbers and less mismatch risk on repeat builds. RSL trades contact capacity for DIN-rail density where the I/O count leaves no other option. Match the family to the cabinet constraint first, then confirm coil voltage against the driving output and contact rating against the actual load — the family choice only pays off if those two checks are done right behind it.
