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Siemens 3RH1921-1EA20 — Contactors

Siemens 3RH1921-1EA20 SIRIUS Auxiliary Switch, 2 N/O, 10 A,

MPN3RH1921-1EA20
Active

Siemens SIRIUS auxiliary switch, 3RH1921-1EA20, 2 N/O contacts, screw-type terminals, snap-on mounting for S0 contactor size, 10 A rated.

Source DocumentedChannel stated on listing & quote
Condition PhotosReal unit photos / video on request
WhatsApp AnswersFast human replies for machine-down parts
Worldwide DispatchDHL/FedEx — transit quoted per order
Independent China distributor & sourcing agent· Listing updated Sep 2026

Specifications

3RH1921-1EA20 — Identification
ParameterValue
Contactor frame sizeS0
3RH1921-1EA20 — Ratings & Performance
ParameterValue
Rated value @ 24 V10 A
Rated value @ 60 V4.7 A
Rated value @ 110 V3 A
Rated value @ 220 V1.2 A
3RH1921-1EA20 — Contacts & Poles
ParameterValue
Auxiliary contact reliability1 faulty switching per 100 million (17 V, 1 mA)
3RH1921-1EA20 — Connection & Mounting
ParameterValue
Conductor cross-section, solid or stranded2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)
Conductor cross-section, finely stranded w/ ferrule2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)
Mounting methodsnap-on mounting
3RH1921-1EA20 — Environmental
ParameterValue
Operating temperature range-25 ... +60 °C
Storage temperature range-55 ... +80 °C
3RH1921-1EA20 — Mechanical
ParameterValue
Width10 mm
Height80 mm
Depth71 mm

Product details

What this auxiliary switch does in the panel

It's the part you add when the main contactor needs to report its position back to the PLC, interlock a second device, or drive a panel light. The screw-type terminals accept 2x (0.5...1.5 mm²) solid or 2x (0.75...2.5 mm²) stranded, and the 10 mm width means it won't eat up DIN rail space the way a separate relay would. Rated at 10 A for AC-12 duty, the contacts handle typical control-circuit loads — PLC inputs, contactor coils, indicator lamps — without derating down to 24 V. The mirror contact feature per IEC 60947-4-1 (verified with 3RT1 contactors) means the N/O contacts cannot weld closed if the main contacts weld, a requirement for safety circuits that monitor contactor state.

Current ratings across the voltage range

The switching capacity varies significantly with applied voltage, which matters when you're mixing control voltages in the same panel. At 24 V the contacts are rated 6 A (with a 10 A rated value for the contact block itself), at 48 V and 60 V it drops to 2 A, at 110 V it's 1 A, at 230 V it's back to 6 A, and at 400 V it handles 3 A. The 230 V figure covers common single-phase control circuits in European panels; the 400 V rating covers line-voltage pilot devices in three-phase motor starters.

Mounting and integration with S0 contactors

Snap-on mounting directly to the contactor — no DIN rail required, no extra brackets. The 71 mm depth and 80 mm height match the S0 contactor envelope, so the assembly stays within the same panel footprint. Designed as a first laterally mountable block, it can sit on either side of the contactor, which helps when you need to stack multiple auxiliary blocks or a pneumatic timer alongside it.

RoHS compliance date is listed as July 1, 2006, covering the original EU directive. The part carries no explicit UL or CSA mark in the evidence, so verify with the factory if your site requires a listed component for the panel certification.

Frequently asked questions

Will the 3RH1921-1EA20 drop into a panel specified around the 3RH2122-1BA40 without rewiring?

Both are SIRIUS auxiliary switches for S0 contactors with the same snap-on mounting and screw terminals, so the physical fit is identical. The 3RH1921-1EA20 carries two N/O contacts; the 3RH2122-1BA40 carries a different contact arrangement, so verify your control logic before swapping.

What compliance documentation does Siemens provide for the 3RH1921-1EA20?

RoHS compliance is documented with a substance prohibition date of July 1, 2006. The mirror contact design is certified per IEC 60947-4-1 when used with 3RT1 contactors.

MPN
3RH1921-1EA20