The Siemens 3RF2120-1AA04 is a single-phase SIRIUS 3RF2 solid-state relay designed for wear-free, noiseless switching of resistive and inductive AC loads. Rated at 20 A (AC-51) with a 48–460 V AC operating voltage range, it is controlled by a 15–24 V DC signal and uses screw terminals for main circuit connections.
Unlike electromechanical relays, this solid-state device has no moving parts, making it ideal for high-switching-frequency applications and noise-sensitive environments. The compact 22.5 mm width saves valuable space, and the unit can be expanded with standardized 3RF29 function modules for load monitoring, power regulation, or terminal covers.
Item No :
3RF2120-1AA04Order(MOQ) :
1Payment :
EXWProduct Origin :
GermanyShipping Port :
Wuhan, Hubei, ChinaLead Time :
3-5 daysWeight :
0.076kgOverview
3RF2120-1AA04 SIMATIC PLC Module
New in stock
Origin from Germany
Payment Method: TT.Western Union
Shipping Method: DHL\UPS\Fedex\EMS\Others
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| Part Number | Description | Key Difference |
|---|---|---|
| 3RF2120-1AA04 | 20 A, 48–460 V AC, 15–24 V DC control (this item) | Standard screw terminal variant |
| 3RF2120-1AA24 | 20 A, 48–460 V AC, 110–230 V AC control | AC control voltage variant |
| 3RF2120-1BA04 | 20 A, 48–460 V AC, instantaneous switching | Non-zero-point switching variant |
| 3RF2150-1AA04 | 50 A, 48–460 V AC, 15–24 V DC control | Higher current rating |
| 3RF2920-0HA16 | Load monitoring module | Optional function module |
| Heatsink | Required for full 20 A rating | Consult datasheet for sizing |
Important: The 20 A rating is the performance capacity of the solid-state relay. The actual permitted rated operational current depends on the connection method, heatsink, and cooling conditions. A suitable heatsink is required to achieve the full 20 A rating. The minimum load current is 100 mA—loads drawing less than this may not switch reliably .
1 × Siemens 3RF2120-1AA04 SIRIUS 3RF2 Solid-State Relay
Note: Heatsink, function modules, and terminal covers are sold separately.
In Stock – Ready to ship immediately
Genuine Siemens Product – Factory original SIRIUS component, Active Product status
Warranty Included – Purchase with confidence
Technical Support – Application and heatsink sizing assistance available
Q1: What is the Siemens 3RF2120-1AA04?
It is a single-phase SIRIUS 3RF2 solid-state relay with a 20 A rating, 48–460 V AC operating voltage, and 15–24 V DC control signal. It uses zero-point switching and screw terminals for wear-free, noiseless load switching .
Q2: Does this device require a heatsink?
Yes. The 20 A rating is the performance capacity. The actual permitted operational current depends on the heatsink and cooling conditions. A suitable heatsink must be used to achieve the full rating. Without adequate cooling, the permissible current is significantly lower .
Q3: What is zero-point switching?
Zero-point switching means the device turns on when the AC voltage crosses zero. This minimizes inrush current and electrical noise, extending the life of resistive loads such as heaters .
Q4: What is the control voltage for this variant?
The 1AA04 variant uses a 15–24 V DC control signal. For an AC control variant, see the 1AA24 model .
Q5: What is the minimum load current?
The minimum load current is 100 mA. Loads drawing less than this may not switch reliably .
Q6: Can I use this for inductive loads?
Yes. The device is designed for switching resistive and inductive loads, such as valves and solenoids. The zero-point switching helps reduce stress on inductive loads .
Q7: What is the power loss at rated current?
The power loss is 28.6 W at the rated current in hot operating condition. This heat must be dissipated by the heatsink .
Q8: What are the dimensions and weight?
Dimensions are 22.5 × 85 × 48 mm (W × H × D). Net weight is 0.076 kg .
Q9: What is the country of origin?
Germany (DE) .
Q10: What should I verify before ordering?
Always verify the exact part number (3RF2120-1AA04 for 15–24 V DC control), confirm your load current and voltage are within the 20 A / 48–460 V AC range, ensure you have a suitable heatsink for your required current, and check whether you need the AC control variant (1AA24) or instantaneous switching variant (1BA04) for your application.
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