The Siemens 3RU2126-1HB0 is a SIRIUS 3RU2 thermal overload relay for motor protection, adjustable from 5.5 … 8.0 A, in size S0 for direct mounting on a SIRIUS 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 | 3RU2126-1HB0 |
|---|---|
| Product | SIRIUS 3RU2 thermal overload relay |
| Size | S0 |
| Current setting range | 5.5 … 8.0 A |
| Trip class | CLASS 10 |
| Auxiliary contacts | 1 NO + 1 NC |
| Rated operating voltage | 690 V |
| Motor power at 400 V (approx.) | 3 kW |
| Mounting | Contactor mounting (size S0) |
| FLA, 3-phase motor at 480 V (UL) | 8 A |
| Power loss (hot, total) | 6.6 W |
| Ambient temperature (operation) | -40 … +70 °C |
| Dimensions (W x H x D) | 45 x 85 x 85 mm |
| Net weight | 0.158 kg |
| Condition | New, original Siemens |
Typical applications
- Star-delta starters (set to 0.58 x motor current in the phase leg)
- Replacement of an aged or damaged overload relay
- Pumps, fans and conveyors in water, HVAC and packaging plants
- Protection of motors with rated current 5.5 … 8.0 A
Compatibility and replacement
Plugs directly onto 3RT2 contactors of size S0 (3RT202x). For separate (stand-alone) mounting Siemens offers a terminal support. For electronic protection with a wider setting range Siemens offers the 3RB3 series.
Frequently asked questions
What motor size does it suit?
Per Siemens the range corresponds to about 3 kW at 400 V (AC-3), but always set it by the motor rated current, not by the kW rating.
How do I set it?
Turn the setting dial to the motor rated current from the nameplate, within 5.5 … 8.0 A.
Can it be mounted on its own?
Yes, with the Siemens terminal support for stand-alone installation; otherwise it plugs straight onto the contactor.
Do you ship to my country, and what is the warranty?
Yes. RendatSP ships worldwide from Yiwu, China, by air in 5 to 7 days once the part is ready, and every part carries a 1-year warranty. Send the order number and quantity on WhatsApp and we will reply with a quotation.
Ordering tips
Send us the full order number from the label of the old part, or a clear photo of the label, together with the quantity you need. We check the number against the current manufacturer data before we quote and tell you if there is a newer replacement.
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.
