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Siemens 3RH1921-2FA31 — Contactors

Siemens 3RH1921-2FA31 SIRIUS Auxiliary Switch Block, 3NO+1NC

MPN3RH1921-2FA31

Siemens SIRIUS auxiliary switch block, 3 NO + 1 NC, spring-loaded terminals, snap-on mounting for 3RT1 contactor relays and motor contactors, IP20 front, 51 mm depth.

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

3RH1921-2FA31 — 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
3RH1921-2FA31 — Contacts & Poles
ParameterValue
Auxiliary contact reliability1 faulty switching per 100 million (17 V, 1 mA)
3RH1921-2FA31 — Connection & Mounting
ParameterValue
Mounting methodsnap-on mounting
3RH1921-2FA31 — Environmental
ParameterValue
Operating temperature range-25 ... +60 °C
Storage temperature range-55 ... +80 °C
3RH1921-2FA31 — Mechanical
ParameterValue
Width44 mm
Height38 mm
Depth51 mm

Product details

It uses spring-loaded terminals for the auxiliary and control circuit connections, accepting 2x (0.5 to 2.5 mm²) solid or stranded wire without ferrules, or 2x (0.5 to 1.5 mm²) with core-end processing. The block measures 51 mm deep by 44 mm wide by 38 mm high and carries an IP20 protection rating on the front face.

Lifecycle and replacement

This part is a phased-out product. The manufacturer lists the successor as the SIRIUS 3RH2 series auxiliary switch blocks. For new designs or a direct drop-in replacement, evaluate the 3RH2 series — the 3RH2131-2AK60 (3 NO + 1 NC, spring terminals, size S00) is the closest functional peer, though it mounts on size S00 contactors rather than the S0 through S12 range of the original.

The AC-15 rated operational current varies by voltage: 10 A at 24 V, 6 A at 125 V, 6 A at 230 V, 6 A at 250 V, 3 A at 400 V, and 1 A at 690 V. These are the inductive-load ratings for solenoid and contactor coils — the most common duty for an auxiliary block. The DC switching ratings follow a different curve: 6 A at 24 V, 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, 0.5 A at 440 V, and 0.26 A at 600 V. The 10 A maximum applies across the board, but the voltage-specific derating is what governs real-world fit.

The spring-loaded terminals accept 2x (0.5 to 2.5 mm²) without ferrules or 2x (0.5 to 1.5 mm²) with ferrules; AWG equivalents are 2x (20 to 14). The 51 mm depth keeps the block within the envelope of the contactor it mounts on, so it does not increase the panel depth beyond the base device.

Frequently asked questions

Where can I buy 3RH1921-2FA31 and get a price?

The 3RH1921-2FA31 is sourced and quoted to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time — submit an RFQ for a firm price and lead time.

What is the closest functional second-source for 3RH1921-2FA31?

The closest functional peer is the SIRIUS 3RH2131-2AK60, which also offers 3 NO + 1 NC contacts with spring-loaded terminals. The key difference is mounting size: the 3RH1921-2FA31 fits contactors in sizes S0 through S12, while the 3RH2131-2AK60 is sized for S00 contactors. Verify the base contactor frame size before substituting.

What does the note 'with 3RT1' mean for this part?

The note indicates the 3RH1921-2FA31 auxiliary switch block is designed to mount directly onto 3RT1 series contactor relays and power contactors. It snaps onto the front of the contactor without additional hardware.

What is the depth of 3RH1921-2FA31?

The depth is 51 mm. Width is 44 mm and height is 38 mm. These dimensions keep the auxiliary block within the contactor footprint when mounted.

Will 3RH1921-2FA31 drop into a panel specified around 3RH2131-2AK60 without rewiring?

Not directly. Both use spring-loaded terminals and the same contact arrangement (3 NO + 1 NC), but the 3RH1921-2FA31 mounts on contactors in sizes S0 through S12, while the 3RH2131-2AK60 is sized for S00 contactors. If the base contactor frame is S00, the 3RH1921-2FA31 will not snap on. Wiring is compatible if the terminal function mapping matches, but the mechanical fit must be verified first.

MPN
3RH1921-2FA31