Siemens 3RH1921-1HA22 Contactor Side-Mount Accessory

Full Product Name: SIRIUS side-mounted auxiliary switch block, 4-pole, 2NO+2NC, screw terminals

Product Status: Discontinued (PLM PM500). It is an older accessory for 3RT1 contactors. The new-generation replacement series is 3RH29xx

1. Model Nomenclature

3RH: SIRIUS auxiliary switches / contactor relay accessories

19: External side-mounted auxiliary contacts for contactors

21: Side snap-on mounting, fits S0～S3 contactor sizes

1: Screw terminals; 2 = spring-cage terminals (3RH1921-2HA22)

HA: 4-pole side-mounted contact block

22: Contact configuration 2 Normally Open + 2 Normally Closed (2NO+2NC)

2. Key Technical Parameters
3. Contacts: 2NO+2NC, 4-pole, compliant with EN 50012
4. Mounting: Snap-on side installation on the contactor
5. Compatible base unit: SIRIUS 3RT1 motor contactors, frame sizes S0 / S2 / S3
6. Terminals: Screw type, wire cross-section 0.5~2.5 mm²
7. Protection: Front face IP20
8. Rated insulation voltage: 690 V (pollution degree 3), impulse withstand voltage 6 kV
9. Endurance: Mechanical life 10 million operating cycles; AC-15 230V electrical life 200,000 cycles
10. Operating temperature: -25 ~ +60 °C; storage temperature: -55 ~ +80 °C
11. Contact reliability: 17 V / 1 mA, max 1 failure within 100 million operations
12. Application Scenarios

Side expansion of auxiliary contacts for 3RT1 (S0~S3) AC contactors

PLC feedback signals, status indication, interlock circuits, fault signal output

Motor start-stop control circuits, fan & water pump control panels, low-voltage switchgear cabinets

Note: Side auxiliary switches can only be fitted on the left side of the contactor. The total number of NC contacts is limited; positively driven contacts must be verified for safety interlock applications.

4. Replacement Selection (Discontinued Upgrade)

Original model discontinued. The corresponding side-mounted unit for new 3RT2 (S0~S3) contactors:

3RH2921-1DA22 (screw terminal, 2NO+2NC side-mounted auxiliary switch)

5. Troubleshooting & Inspection Guidelines
6. Common failures: Contact oxidation, contact burning, loose snap-fit clips leading to intermittent feedback signals
7. Multimeter test: With the contactor de-energized, NC contacts shall be conducting and NO contacts open; contact status flips when the coil is energized
8. Wiring check: Tighten all terminal screws firmly; loose thin wires frequently cause unstable PLC digital inputs
9. Replacement: Direct snap-on disassembly without touching the main power circuit; always test interlock logic after replacement
10. Cross-reference List for the Same Series

3RH1921-1HA22: Screw terminals, 2NO+2NC, side mount S0–S3 (Discontinued)

3RH1921-2HA22: Spring-cage terminals, same contact configuration (Discontinued)

3RH2921-1DA22: New-generation screw-type side-mounted 2NO+2NC (Replacement model)

Siemens 3RT1 Contactor Replacement Overview

3RT1 (S00~S3, ≤95A) is discontinued (PLM PM500). First-choice official direct replacement: 3RT2 (imported SIRIUS Innovation series). For cost-saving domestic alternatives, select 3RT6 / 3RT5. Larger frame 3RT1 (>95A) remains available with no forced phase-out schedule

1. 3RT2 [Imported, Preferred OEM Replacement]

Series: 3RT20xx, direct replacement for legacy 3RT10xx

Frame size match: S00 / S0 / S2 / S3, AC-3 current range 7A~95A

Replacement rule:

Example: 3RT1024-1BB40 → 3RT2024-1BB40. Keep coil voltage and rated current unchanged; only change the middle digit from 1 to 2.

Critical compatibility note (relevant to your 3RH1921 auxiliary contacts):

Old 3RH1921 cannot be used on 3RT2; you must upgrade to 3RH2921 series auxiliary switches together with the contactor body.

2. Large-size 3RT1 (S6 / S10 / S12, Still Active, Not Discontinued)

S6 (3RT105×, Frame S6, 115A~150A, 55kW~75kW @400V)

Complete model examples: 3RT1054-6AF36, 3RT1055-6NB36

S10 (3RT106×, Frame S10, 185A~225A, 90kW~110kW @400V)

S12 (3RT107×, Frame S12, 265A~300A, 132kW~160kW @400V)

S14 (Extra-large frame, still available)

3RT1096: 400A / 200kW

3RT1097: 500A / 250kW

3. Dedicated Accessories for S6/S10/S12 (Not Interchangeable with S00~S3)

(1) Side-mounted auxiliary switches (Base unit already has built-in 2NO+2NC; add-on optional)

S6: 3RH1951

S10: 3RH1961

S12: 3RH1971

Important reminder: 3RH1921 (for small frames) cannot be installed here due to incompatible snap-in geometry.

(2) Plug-in thermal overload relays (direct plug-on mounting with 3RT1)

S6: 3RU1156

S10: 3RU1166

S12: 3RU1176

(3) Mechanical interlocks (for reversing contactor pairs)

S6: 3RT1951

S10: 3RT1961

S12: 3RT1971

4. Coil Voltage Suffix Codes (Universal for all frames)

1AB36: AC/DC 24 V

1AD36: AC/DC 48 V

6AF36: AC/DC 110~127 V

6AU36: AC/DC 200~277 V (wide-voltage coil)

5. Phase-out Boundary Rules (Critical)
6. 3RT101~3RT104 (S00~S3, ≤95A): PM500, fully discontinued. Must migrate to 3RT2 / 3RT6.
7. 3RT105~3RT107 (S6/S10/S12): PM300, active production, long-term supply, no end-of-life plan.
8. Future upgrade path (if needed): 3RT105 → 3RT205; 3RT106 → 3RT206; 3RT107 → 3RT207. Replace accessories with 3RH2951/2961/2971 accordingly.
9. Popular Complete Order Numbers
10. 3RT1054-6AF36｜S6, 115A, AC/DC 110V coil
11. 3RT1055-6NB36｜S6, 150A, wide-voltage coil
12. 3RT1064-6AU36｜S10, 185A, AC/DC 240V coil
13. 3RT1065-6AU36｜S10, 225A, AC/DC 240V coil
14. 3RT1075-6AU36｜S12, 265A
15. 3RT1076-6AU36｜S12, 300A