Siemens 5SV and 5SU SENTRON RCD: Full Range Review
What does the Siemens SENTRON RCD range cover? Siemens splits residual current protection into three product lines: the 5SV RCCB (current-only, IEC 61008), the 5SU1 and 5SV1 RCBO (combined MCB and RCD, IEC 61009), and the 5SM3 module for smooth DC fault current. A panel builder without overcurrent protection already installed on a circuit needs the RCBO; one with existing MCBs per circuit only needs the RCCB in front of them. This review covers the 5SV3/5SV4/5SV6 sub-series, the SIGRES coating option, 5SM2 residual current relays for feeders above 125 A, and where each Siemens part sits against Schneider Acti9 and ABB F200.
Siemens 5SV RCCB Range: 5SV3, 5SV4, 5SV6
The 5SV RCCB line covers 2-pole and 4-pole devices from 16 A to 125 A rated current, in Types AC, A and F. Siemens splits the family by generation and feature set rather than by a single catalog number: 5SV3 is the base Type AC/A series, 5SV4 adds Type F coverage for single-phase variable-frequency loads, and 5SV6 extends to higher rated currents and four-pole feeder applications. Siemens 5SV RCCB models are stocked in our residual current devices collection.
None of the three carries overcurrent protection. Each 5SV device must be backed by an MCB or fuse sized to the conditional short-circuit current stated on the datasheet, typically 6 or 10 kA with a compliant upstream device. Sensitivity choices run 10, 30, 100, 300 and 500 mA — 30 mA is the version specified for socket circuits and personal protection, while 100-500 mA units belong on distribution boards where the goal is fire protection rather than shock protection, since a lethal current is reached well before 100 mA. Selectable IΔn switches exist on some feeder-oriented 5SV6 units, useful when one device covers several downstream circuits with different risk profiles.
Siemens 5SU1 and 5SV1 RCBO: Combined Protection in One Module
The 5SU1 is Siemens' compact 1P+N RCBO, combining an MCB (B or C curve, 6-40 A typical) with an RCD block in a single DIN-rail module the same width as a standalone MCB. It suits final circuits — lighting, sockets, small appliance loads — where board space is limited and one device per circuit is the design intent. 5SU1 and 5SV1 RCBO models are listed in our RCBOs collection. The 5SV1 designation appears on some regional RCBO variants with the same combined function; the practical difference between 5SU1 and 5SV1 in a given market is usually curve and current range coverage, not protection principle.
Compare this to Schneider's approach. Acti9 Vigi iC60 is an add-on block that clips onto an existing iC60 MCB, so a panel already stocked with iC60 breakers only needs the Vigi add-on, not a full RCBO replacement. Siemens 5SU1 is one-piece from the start. Neither approach is objectively better; it depends on whether the board is a new build or a retrofit onto MCBs already installed. For the broader distinction between the two topologies, see RCCB vs RCBO differences.
5SM3 Type B and 5SM2 Residual Current Relays
The 5SM3 is Siemens' Type B module, detecting smooth DC residual current in addition to the AC and pulsating DC that Type A and F already cover. It is the specified device for three-phase EV chargers, transformerless PV inverters and VFD outputs where a rectifier bridge can produce a genuine DC fault current — a waveform that a Type A device cannot reliably detect and can, in the worst case, desensitize entirely. 5SM3 units are physically larger than 5SV RCCBs because the toroidal core and electronics needed for DC detection take more room. For the full Type A vs Type B decision on these load types, see RCD for EV charger circuits.
Above roughly 125 A, Siemens moves to the 5SM2 residual current relay: a separate sensing relay wired to an external toroid that clamps around the phase conductors, paired with a shunt trip on the upstream breaker. This is the standard approach for large feeders and incoming supplies, where a fixed RCCB frame isn't available at the required current rating. ABB's equivalent is the RD3 relay family; Schneider's is Vigirex.
Formula: RCD Selectivity (Discrimination) — Source: IEC 60364-5-53 / manufacturer selectivity guides
IΔn(upstream) ≥ 2 × IΔn(downstream), with t(upstream) > t(downstream)
| Symbol | Description | Unit |
|---|---|---|
| IΔn(upstream) | Rated residual operating current of the upstream (time-delayed/selective) device | mA or A |
| IΔn(downstream) | Rated residual operating current of the downstream (instantaneous) device | mA |
| t(upstream) | Trip delay of the upstream device relative to the downstream device | ms |
Apply this when a 5SM2 relay on the incoming feeder backs up 5SV or 5SU1 devices on final circuits: set the upstream sensitivity at least double the downstream value and confirm the upstream unit carries a time delay — an S-type or selective relay setting — so a fault on one final circuit trips only that circuit's device.
SIGRES Coating for Humid and Corrosive Sites
SIGRES is Siemens' conformal coating option applied to 5SV devices intended for damp, dusty or chemically aggressive environments: coastal installations, agricultural buildings, wastewater plants. The coating protects contact surfaces and the PCB from condensation-driven corrosion and airborne contaminants that would otherwise cause a device to nuisance-trip or, worse, fail to trip when required. It doesn't change the electrical rating or sensitivity class. It's a build variant of the same 5SV base part.
What we see in the field: RCDs installed in unheated plant rooms near coastal sites fail early, and it's rarely the electronics — it's corrosion creeping into the contact mechanism. A SIGRES-rated device costs more up front but avoids the repeat nuisance-trip callouts that eat into a maintenance budget faster than the price difference.
Choosing Between 5SV RCCB, 5SU1 RCBO and 5SM3
Start with what's already on the board. If MCBs are already installed and only earth-leakage protection is missing, a 5SV RCCB in front of the group is the compact option, provided the group's cumulative earth leakage stays well under the RCD's sensitivity to avoid nuisance tripping. If the circuit needs both functions from scratch, 5SU1 saves board width over a separate MCB-plus-RCCB pair. If the load includes an EV charger, PV inverter, or a VFD with smoothing capacitors after the rectifier, only 5SM3 (or a Type A device combined with a certified 6 mA RDC-DD) is compliant. Our RCD sensitivity guide covers the 10-500 mA decision in more depth, and RCD types explained covers the type letters.
| Criteria | Siemens 5SV RCCB | Siemens 5SU1 RCBO | Siemens 5SM3 |
|---|---|---|---|
| Protection function | Earth leakage only | Earth leakage + overload/short-circuit | Earth leakage, includes DC residual |
| Types available | AC, A, F | AC, A (typical) | B |
| Typical use | Group of circuits behind existing MCBs | Single final circuit, new board | EV charger, PV inverter, VFD output |
| Rated current range | 16-125 A | 6-40 A (typical) | 25-63 A (typical) |
| Board width | 2P/4P module | 1P+N, single MCB width | Wider than 5SV, DC electronics |
Siemens vs Schneider Acti9 vs ABB F200: Where SENTRON Sits
Functionally, the three brands converge. All three now default to Type A, all three publish a Type B range, and all three offer a super-immunized or coated variant for demanding sites. The differences that matter at spec time are packaging — Schneider's Vigi add-on block versus Siemens' and ABB's one-piece RCBOs — and which specific current and sensitivity combinations sit in stock at a given distributor. A full breakdown of trip curves, IΔn options and physical width across all three is in our RCCB brand comparison. The underlying engineering background for the whole product category is in our RCD protection guide.
Frequently Asked Questions
What's the difference between Siemens 5SV3, 5SV4 and 5SV6?
They're generation and feature variants within the same 5SV RCCB family rather than separate device classes. 5SV4 specifically adds Type F coverage for single-phase variable-frequency loads; 5SV6 extends the range to higher rated currents and four-pole feeder use. Confirm the exact type and current rating on the datasheet rather than assuming by series number alone.
Does a Siemens 5SU1 RCBO need a separate MCB?
No. The 5SU1 already integrates an MCB, either B or C curve, with the RCD block in one DIN-rail module, so no additional overcurrent device is needed on that circuit. A standalone 5SV RCCB, by contrast, always needs a backup MCB or fuse.
Is the Siemens 5SM3 just a 5SV RCCB with a different type letter?
Not electrically. The 5SM3 uses a different core and detection electronics capable of sensing smooth DC residual current, which a standard AC/A/F 5SV core cannot detect. It's also physically larger to accommodate that circuitry.
When should I use a 5SM2 relay instead of a 5SV RCCB?
Once the feeder current exceeds the largest fixed 5SV frame, typically above 125 A, a 5SM2 residual current relay with an external toroid and shunt trip is the standard route rather than a fixed RCCB body.
Is SIGRES coating necessary for indoor panels?
Not for a dry, climate-controlled panel room. It matters where humidity, dust or corrosive vapor is present — coastal sites, agricultural buildings, wastewater plants — and where nuisance trips or premature failure from corrosion would otherwise be a recurring problem.
Can Siemens 5SV RCCBs be mixed with ABB or Schneider MCBs on the same board?
Electrically, yes. An RCCB only needs a compliant backup device with adequate short-circuit rating, regardless of brand. Mechanically, check DIN-rail module width and any brand-specific busbar or comb requirements before mixing manufacturers on the same board.
Conclusion
Siemens covers the residual current spectrum with three distinct product lines rather than one universal part: 5SV for RCCB-only applications behind existing overcurrent protection, 5SU1/5SV1 for combined RCBO protection in a single module, and 5SM3 for smooth DC fault current on EV, PV and VFD circuits. SIGRES coating and the 5SM2 relay round out the range for harsh environments and large feeders. Match the type to the load's actual fault-current waveform before comparing brands. That decision, not the manufacturer name on the front cover, determines whether the installation is compliant.
