Siemens SIRIUS 3RV2 MPCB: Full Range Review
What does the Siemens SIRIUS 3RV2 range cover? The 3RV2 is Siemens' current motor protection circuit breaker (MPCB) family under the SIRIUS modular system, built to IEC 60947-4-1 and spanning frame sizes S00 through S3 with thermal settings scaling from a fraction of an amp up toward the roughly 100 A ceiling of the largest frame. Pick the wrong frame or the wrong variant and the breaker either won't cover the motor's full-load current or sits oversized in the panel for no reason. This review covers the frame lineup, thermal-magnetic versus magnetic-only variants, trip class, coordination with 3RT2 contactors, the link-module mounting system, and how the family compares to the older SIRIUS generation and to competing European MPCBs.
How the 3RV2 Fits Into the SIRIUS Modular System
SIRIUS is Siemens' umbrella brand for motor control components: contactors (3RT2), overload relays (3RU2, 3RB3), and the 3RV2 circuit breaker itself. The 3RV2 isn't a standalone product line. It is designed from the start to bolt onto a 3RT2 contactor through a link module, forming what Siemens calls a load feeder. That mechanical relationship drives most of the design choices inside the 3RV2 — frame width, terminal position, even the shape of the front dial are set to match the contactor it will sit on top of.
Three protective functions live in the one housing: an adjustable bimetal overload element dialed to the motor's full-load current (FLC), a fixed magnetic trip that responds only to short-circuit-level current (roughly 12-13x the dial setting), and a manual handle that doubles as the local isolation point. What we see in the field is that panel builders standardizing on SIRIUS often pick the 3RV2 purely for the link-module fit, then discover afterward that the frame size also happens to match their motor's FLC. The mechanical decision and the electrical decision aren't always made in that order, and it shows in how many panels get built around a contactor first.
Frame Sizes S00 to S3: How the Range Scales
Frame size in the 3RV2 family tracks physical width and current class together. S00 is the narrowest frame and covers the lowest thermal settings in the range, the frame most small pump and fan motors land on. S0 steps up both the physical width and the setting window for mid-range motors. S2 and S3 carry the family up toward its roughly 100 A ceiling, and the frame gets correspondingly wider to carry the busbar and terminal ratings a breaker that size needs.
The consequence for a panel builder: frame size isn't just a current decision, it's a layout decision. A DIN rail populated with S00 frames packs far more feeders per meter than the same rail populated with S3 frames. Get the frame sizing wrong on a multi-feeder panel and the enclosure gets bigger, not just the bill of materials.
| Criteria | S00 | S0 | S2 / S3 |
|---|---|---|---|
| Relative current class | Lowest in the range | Low-mid | Mid up to the ~100 A ceiling |
| Physical width per pole | Narrowest | Narrow | Progressively wider |
| Typical motor size | Small pumps, fans, fractional-to-a-few-amp loads | General small-to-medium motors | Medium-to-large motors near the frame's setting ceiling |
| Link-module fit | Matches smaller 3RT2 frames | Matches mid 3RT2 frames | Matches larger 3RT2 frames |
Thermal-Magnetic vs Magnetic-Only: 3RV2011, 3RV2021, 3RV2031
Most of the 3RV2 lineup, including the 3RV2011, 3RV2021 and 3RV2031 series, ships thermal-magnetic: adjustable bimetal overload plus fixed magnetic short-circuit trip, in one unit. That's the default choice for a straightforward motor branch circuit where a single device should handle overload, short circuit and isolation.
Magnetic-only variants exist for a different job. They drop the thermal element entirely and trip only on short-circuit current, leaving overload protection to a separate device, typically a 3RU2 thermal overload relay or a 3RB3 electronic overload relay mounted on the contactor. That split makes sense when the application wants finer overload protection than a bimetal dial gives — a 3RB3 electronic relay reads true motor current and can add features like ground-fault or thermistor input — or when the overload relay is standardized separately from the breaker across a plant.
Choosing between the two isn't about one being better. It's about where the overload decision sits. Thermal-magnetic keeps the whole protection function in one device on the DIN rail, simpler to spec and simpler to replace. Magnetic-only pushes overload sensing onto the relay, which can be worth it on critical motors but adds a part number and a wiring step most feeders don't need.
Trip Class and Coordination With 3RT2 Contactors
The 3RV2 family runs Class 10 as standard, per IEC 60947-4-1: from a cold start, the thermal element must trip within 10 seconds at 7.2 times the dial setting (see MPCB trip classes 10, 20 and 30 for how this compares against slower-tripping classes for high-inertia loads). That ceiling is tight enough for the great majority of direct-on-line motors, whose start current settles well before the 10-second mark.
Formula: Trip Class Time Reference — Source: IEC 60947-4-1, Table 7
ttrip ≤ tclass at I = 7.2 × Ie (cold start)
| Symbol | Description | Unit |
|---|---|---|
| ttrip | Actual thermal trip time at 7.2× the dial setting | s |
| tclass | Class ceiling (10 s for Class 10) | s |
| Ie | Thermal overload current setting, dial value set to motor FLC | A |
Trip class alone doesn't settle coordination. Siemens publishes tables pairing each 3RV2 frame and setting with a specific 3RT2 contactor size and declares the resulting Type (see MPCB Type 1 vs Type 2 coordination for the full definitions). Type 2 means that after a short-circuit event the contactor contacts may show light welding that's easily separated, and the feeder stays serviceable without replacing parts; Type 1 allows more damage as long as it doesn't endanger anyone nearby. The published table is the only reliable source for which 3RV2 and 3RT2 pairing hits Type 2 at a given short-circuit rating. Matching frames by current alone doesn't guarantee it.
Link Modules: Mounting the 3RV2 Directly to a 3RT2 Contactor
A link module is the mechanical and electrical bridge between a 3RV2 breaker and a 3RT2 contactor. It replaces three-phase jumper wiring with a bolt-on busbar connector, so the two devices snap together into a single feeder block on the DIN rail. Wire once into the top of the breaker and once out of the bottom of the contactor, and the phase connections between them are handled by the module, not loose leads. For more on how the breaker and contactor combine into a complete branch circuit, see MPCB plus contactor: building a motor starter.
This is where frame matching matters again: the link module is sized to a specific 3RV2 frame and a specific 3RT2 frame, so specifying the breaker without checking the paired contactor frame is a common way a feeder order comes back short a part number. Some panel builders standardize an entire line on one contactor frame and then discover the smaller-motor feeders needed a different link module than the one ordered in bulk. Worth checking before a large order goes in, not after.
Terminals, Accessories and Where 3RV2 Sits Against Schneider and ABB
The 3RV2 range offers screw and spring cage-clamp terminal options across most frames, plus the accessory categories common to the whole MPCB class: auxiliary contact blocks for remote status, alarm switches that report a trip distinct from a manual open, and door-coupling rotary handles for panels where the breaker sits behind a closed enclosure door. None of these change the protection function. They change how the feeder reports status and how it's operated from outside the panel.
Set against the rest of the field: Schneider's TeSys GV2/GV3/GV4 and ABB's MS116/MS132/MS165 cover the same three-function combination — adjustable thermal, fixed magnetic, manual isolation — at Class 10, each with its own coordination tables and each with a magnetic-only variant for pairing with a separate overload relay. The practical differences sit in frame breakpoints, terminal style, phase-loss sensitivity, and how deep the link-module or clip-on accessory ecosystem goes for each brand's own contactor line; see the Schneider GV2 vs ABB MS132 vs Siemens 3RV2 comparison for the full breakdown. This depends on which contactor family a panel is already standardized on. Swapping breaker brands mid-line usually means swapping the link modules and coordination tables along with it, not just the part number on the breaker.
Frequently Asked Questions
What frame sizes does the Siemens SIRIUS 3RV2 cover?
S00, S0, S2 and S3, scaling from the smallest thermal settings up toward the family's roughly 100 A ceiling. Frame width increases at each step to carry the higher terminal and busbar ratings.
What's the difference between a thermal-magnetic 3RV2 and a magnetic-only variant?
Thermal-magnetic units, including the 3RV2011, 3RV2021 and 3RV2031 series, combine adjustable overload and fixed short-circuit tripping in one device. Magnetic-only variants drop the thermal element and rely on a separate 3RU2 or 3RB3 overload relay for overload protection.
Which contactor does the 3RV2 pair with, and how?
The 3RV2 is designed to mount directly onto a 3RT2 contactor through a link module, which carries the three-phase connection between them without separate jumper wiring. The pairing has to match on frame size, not just current rating.
What trip class does the SIRIUS 3RV2 use?
Class 10 as standard, per IEC 60947-4-1: the thermal element trips within 10 seconds at 7.2 times the dial setting from a cold start. That covers the great majority of direct-on-line motor starts.
Can a 3RV1 be swapped directly for a 3RV2?
Not automatically. The 3RV2 is the current generation and the two families differ in frame breakpoints and accessory fit, so a like-for-like swap needs the cross-reference confirmed against the specific 3RV1 part before ordering.
Does the SIRIUS 3RV2 protect against phase loss?
Yes. The family includes differential/phase-loss tripping that reacts to single-phasing faster than the bimetal alone would, which matters because the remaining phases see a current rise of roughly 1.7x when one phase is lost.
Conclusion
The SIRIUS 3RV2 covers frame sizes S00 through S3 at Class 10, in both thermal-magnetic and magnetic-only builds, designed from the start to mount onto a 3RT2 contactor through a link module. Getting a 3RV2 feeder right means matching three things at once: the frame to the motor's FLC, the link module to the paired contactor frame, and the coordination Type to what the published table declares for that pairing. Current rating alone doesn't settle any of the three. For background on trip-class and coordination fundamentals, or how the 3RV2 stacks up against Schneider and ABB, see the MPCB engineering guide. Stoklink stocks genuine motor protection circuit breakers and manual motor starters across the Siemens, Schneider and ABB ranges, alongside the contactors and thermal overload relays that complete the feeder.
