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Siemens 3RH2122-1AN20 Specs: 220V AC Contactor Relay Guide
The Siemens 3RH2122-1AN20 is a SIRIUS 3RH2 contactor relay with a 220V AC, 50/60Hz operating coil and four instantaneous contacts arranged as 2 normally open (NO) and 2 normally closed (NC). It has an S00 frame, screw terminals, and a 45 mm housing width. Designed for industrial control circuits, it provides electrically operated switching for interlocking, signaling, and machine sequencing. The most important replacement checks are the exact coil voltage, contact arrangement, switching duty, and terminal configuration.
Siemens 3RH2122-1AN20 Technical Specifications
Unlike a power contactor used to switch motor supply current, this contactor relay is designed for auxiliary and control-circuit switching. Its coil ratings and contact ratings must be evaluated separately.
| Specification | Details |
|---|---|
| Manufacturer | Siemens |
| Product family | SIRIUS 3RH2 |
| Complete part number | 3RH2122-1AN20 |
| Product type | Contactor relay / auxiliary contactor |
| Frame size | S00 |
| Contact configuration | 2 NO + 2 NC |
| Contact operation | Instantaneous |
| Rated coil voltage | 220V AC |
| Coil frequency | 50/60Hz |
| Coil operating range at 50Hz | 0.8–1.1 × rated voltage |
| Coil operating range at 60Hz | 0.85–1.1 × rated voltage |
| Coil pickup consumption | 33 VA |
| Coil holding consumption | 4.4 VA |
| AC-15 current at 230V | 10 A |
| AC-15 current at 400V | 3 A |
| DC-13 current at 24V | 10 A, single current path |
| Rated insulation voltage | 690V AC |
| Rated impulse withstand voltage | 6 kV |
| Terminal connection | Screw terminals |
| Mounting | 35 mm DIN rail or screw mounting |
| Dimensions (W × H × D) | 45 × 57.5 × 73 mm |
| Front protection rating | IP20 |
| Operating temperature | -25°C to +60°C |
| Mechanical service life | 30 million operating cycles, typical for the contactor relay without added auxiliary blocks |
| Net weight | Approximately 0.234 kg |
Technical source: Siemens 3RH2122-1AN20 official datasheet. Ratings are subject to the specified utilization categories and operating conditions.
How the 220V AC Coil and 2NO+2NC Contacts Work
The 3RH2122-1AN20 uses an electromagnetic coil to operate its four control contacts. When the specified 220V AC supply is applied across the coil terminals, the armature moves and changes the state of the contacts. When the coil is de-energized, the contacts return to their normal positions.
The two NO contacts close when the relay operates. The two NC contacts open at the same time. This arrangement allows one relay to provide several control signals from a single operating command.
| Contact type | Coil de-energized | Coil energized | Typical function |
|---|---|---|---|
| 2 × NO | Open | Closed | Control commands, status signaling |
| 2 × NC | Closed | Open | Interlocking, complementary control signals |
For example, a machine control circuit may use one NO contact to activate a secondary control circuit and another to provide a status signal. The NC contacts can be included in separate interlocking paths that must open when the relay operates.
The auxiliary contacts indicate the relay’s switching state. They do not independently confirm that a connected motor is rotating or that an external mechanical process has completed.
Why the 220V AC Coil Rating Matters
The coil rating is a critical selection parameter. Siemens specifies a nominal control supply of 220V AC at both 50Hz and 60Hz for the 3RH2122-1AN20.
According to the datasheet, its operating voltage range is:
- 50Hz: 0.8–1.1 times the rated coil voltage.
- 60Hz: 0.85–1.1 times the rated coil voltage.
The published pickup consumption is 33 VA, while holding consumption is 4.4 VA. This difference matters when sizing the control transformer, selecting upstream switching devices, and evaluating a PLC output interface.
A coil may require substantially more apparent power during pickup than while remaining energized. Designers should therefore check the starting demand rather than sizing the control circuit from holding consumption alone.
The 3RH2122-1AN20 must not be confused with a 24V DC or 110V AC contactor relay. Applying the wrong coil voltage can prevent reliable operation or damage the equipment.
Contact Ratings for AC and DC Control Loads
The contact switching capacity depends on the utilization category and operating voltage. Siemens specifies the following ratings for the standard auxiliary contacts.
| Utilization category | Operating voltage | Rated operational current |
|---|---|---|
| AC-15 | 230V AC | 10 A |
| AC-15 | 400V AC | 3 A |
| AC-15 | 500V AC | 2 A |
| AC-15 | 690V AC | 1 A |
| DC-13, one current path | 24V DC | 10 A |
| DC-13, one current path | 110V DC | 1 A |
| DC-13, one current path | 220V DC | 0.3 A |
AC-15 applies to switching electromagnetic control loads, including contactor coils. DC-13 applies to DC electromagnetic loads, which can be more demanding to interrupt because the current has no natural zero crossing.
These ratings explain why contact selection cannot be based on the highest listed current alone. The actual load voltage, utilization category, required switching frequency, and electrical endurance must all be considered.
The 3RH2122-1AN20 should not be used as a direct substitute for a motor power contactor. Its contacts are intended for control switching, not for replacing the main poles of a motor starter.
3RH2122-1AN20 vs Other Siemens 3RH2 Relays
Several Siemens SIRIUS contactor relays have similar housings and four control contacts. Their coil specifications, contact arrangement, and terminals can differ significantly.
| Model | Coil voltage | Contacts | Terminals |
|---|---|---|---|
| 3RH2122-1AN20 | 220V AC, 50/60Hz | 2NO + 2NC | Screw |
| 3RH2122-1AF00 | 110V AC, 50/60Hz | 2NO + 2NC | Screw |
| 3RH2122-1AP00 | 230V AC, 50/60Hz | 2NO + 2NC | Screw |
| 3RH2131-2BB40 | 24V DC | 3NO + 1NC | Spring-loaded |
For example, the 3RH2122-1AP00 has a nominal 230V AC coil, while the 3RH2122-1AN20 is specified for 220V AC. Their actual suitability depends on the available control voltage and the manufacturer’s operating limits. A different coil designation should not be ignored during replacement.
The Siemens 3RH2131-2BB40 contactor relay guide covers a 24V DC version with 3NO+1NC contacts and spring-loaded terminals. It is a related product for comparison, not a direct replacement.
Installation and Replacement Checks
The 3RH2122-1AN20 supports installation on a 35 mm DIN rail or by screw mounting. Its S00 dimensions make it suitable for compact control-panel layouts, provided the required clearances are maintained.
When replacing an existing unit, first isolate the control supply and verify the absence of voltage. The coil circuit and all auxiliary contact circuits must be made safe before wiring is removed.
Check the following before installing the replacement:
- Coil supply: Verify 220V AC and the correct operating frequency.
- Contact arrangement: Confirm that the application requires 2NO+2NC, not 3NO+1NC or 4NO.
- Terminal layout: Compare the original wiring diagram with the new device markings.
- Switching ratings: Confirm the AC-15 or DC-13 rating for every connected load.
- Mounting space: Verify S00 dimensions, rail compatibility, and installation clearances.
- Coil control: Check that the control transformer or switching device can accommodate the coil pickup demand.
For applications requiring additional switching paths, Siemens offers separate auxiliary contact blocks. The Siemens 3RH2911-1HA11 auxiliary contact block guide explains a 1NO+1NC accessory. Its mechanical compatibility must be verified for the specific contactor relay before use.
What Information Should Buyers Provide?
When sourcing a replacement, the complete order number is more reliable than a general description such as “Siemens 220V relay.” A similar-looking device may have a different contact arrangement, coil frequency, or terminal style.
For a quotation or replacement review, prepare the complete 3RH2122-1AN20 reference, required quantity, current installation details, control voltage, product condition requirements, and destination.
Related components can be found in the Siemens low-voltage control and distribution catalogue. For model-specific enquiries, use the Siesource contact page and include a photograph of the existing relay label when possible.
Frequently Asked Questions
What is Siemens 3RH2122-1AN20 used for?
It is a SIRIUS 3RH2 contactor relay used for control-circuit switching, interlocking, signaling, and machine sequencing. It has two normally open and two normally closed contacts.
What is the coil voltage of 3RH2122-1AN20?
Its rated coil voltage is 220V AC at 50Hz or 60Hz. The specified operating range depends on the supply frequency.
What is the AC-15 rating at 230V?
Siemens specifies a rated operational current of 10 A at 230V AC under the AC-15 utilization category.
Can a 230V AC contactor relay replace the 3RH2122-1AN20?
Not automatically. The nominal coil voltage, actual control supply, operating range, contact arrangement, terminal configuration, and switching ratings must all be checked.
Can the 3RH2122-1AN20 switch a motor directly?
It is intended for auxiliary and control-circuit switching. A suitably rated power contactor or motor starter should be selected for switching the main motor supply.
Conclusion
The Siemens 3RH2122-1AN20 combines a 220V AC coil, four instantaneous 2NO+2NC control contacts, and screw terminals in an S00 contactor relay. Its published coil consumption and AC-15/DC-13 ratings make it important to evaluate both the operating supply and the controlled loads. For maintenance or replacement, confirm the complete part number and circuit requirements rather than assuming that another SIRIUS relay with a similar appearance is interchangeable.