For motors with a full-load current between 30 … 36 A, the Siemens 3RU2126-4PB0 is the size S0 SIRIUS 3RU2 bimetal overload relay, trip CLASS 10, designed to plug straight onto a 3RT2 contactor. It has 1 NO + 1 NC auxiliary contacts: the NC contact opens the contactor coil circuit on overload and the NO contact can signal the trip to the PLC.
Thermal overload relays protect the motor winding against overheating caused by sustained overload. The relay heats bimetal strips with the motor current; when the current stays above the setting for too long, it trips and switches off the contactor.
See our Siemens industrial controls for matching 3RT2 contactors in size S0.
Technical data
| Siemens order number | 3RU2126-4PB0 |
|---|---|
| Product | SIRIUS 3RU2 thermal overload relay |
| Size | S0 |
| Current setting range | 30 … 36 A |
| Trip class | CLASS 10 |
| Auxiliary contacts | 1 NO + 1 NC |
| Rated operating voltage | 690 V |
| Motor power at 400 V (approx.) | 18.5 kW |
| Mounting | Contactor mounting (size S0) |
| FLA, 3-phase motor at 480 V (UL) | 36 A |
| Power loss (hot, total) | 9.6 W |
| Ambient temperature (operation) | -40 … +70 °C |
| Dimensions (W x H x D) | 45 x 85 x 85 mm |
| Net weight | 0.194 kg |
| Condition | New, original Siemens |
Typical applications
- Motor starters with SIRIUS 3RT2 contactors
- Protection of motors with rated current 30 … 36 A
- Pumps, fans and conveyors in water, HVAC and packaging plants
- Replacement of an aged or damaged overload relay
Compatibility and replacement
Plugs directly onto 3RT2 contactors of size S0 (3RT202x). For separate (stand-alone) mounting Siemens offers a terminal support. If the motor current is at the top of the range, choose the next range up so the setting sits in the middle of the scale.
Frequently asked questions
Can it be mounted on its own?
Yes, with the Siemens terminal support for stand-alone installation; otherwise it plugs straight onto the contactor.
What is the UL full-load current rating?
Per Siemens: 36 A for a 3-phase motor at 480 V.
What does CLASS 10 mean?
The trip class per IEC 60947-4-1: at 7.2 times the setting current the relay trips within 4 to 10 seconds, which suits motors with normal starting.
Can I get a price and delivery time?
Prices are quoted on request. Send the order number, quantity and delivery country on WhatsApp and we will reply with price and delivery time; air shipping is usually 5 to 7 days once ready, with a 1-year warranty.
Before you order
Compare the complete order number on the old unit with this page, including the suffix: in most ranges the last characters set the coil voltage, current range or version. If the label is worn, send us a photo and we will identify the part.
Every part RendatSP supplies is new and original, carries a 1-year warranty and ships worldwide by air in 5 to 7 days once ready (shipping, payment and warranty). Send us the order number and quantity on WhatsApp or through the inquiry form and we will quote the same working day. Agents in Saudi Arabia, Iraq, the UAE, Egypt, Oman, Libya, Morocco, Mauritania, Yemen, Algeria and Jordan.
