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Siemens Overload Relay: Thermal Protection, 3 Poles, 1NO/1NC, Frame Size S0 - IEC Thermal Overload Relays
SiemensIEC Thermal Overload Relays

Siemens Overload Relay: Thermal Protection, 3 Poles, 1NO/1NC, Frame Size S0

The SIEMENS Overload Relay: Thermal Protection (MPN 3RU21261JB0) is an IEC thermal overload relay in Frame Size S0, designed for use with SIRIUS contactors of the same frame size. It features a 1NO/1NC auxiliary…

SKU 3G-OTH-40990

Brand
Siemens
Item
Overload Relay: Thermal Protection, 3 Poles, 1NO/1NC, Frame Size S0
Category
IEC Thermal Overload Relays
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Technical Specifications

Siemens
Manufacturer Part Number
3RU21261JB0
Type
1NO/1NC, Frame Size S0, 7 A – 10 A
Poles
3
Frame Size
S0
Compatible Contactors
Frame Size S0
Auxiliary Contact Form
1NO/1NC
Maximum Voltage Rating
690V AC
Phase Loss Sensitivity
No
Thermal Units Required
None (Relay Includes Integrated Bimetallic Elements)
Terminal Connection Type
Screw Terminals
Compatible Contactor Series
SIRIUS
View Full Spec Sheet

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Siemens Products
3G Electric (S) Pte. Ltd. — Singapore

Product Description

The SIEMENS Overload Relay: Thermal Protection (MPN 3RU21261JB0) is an IEC thermal overload relay in Frame Size S0, designed for use with SIRIUS contactors of the same frame size. It features a 1NO/1NC auxiliary contact form, screw terminals, and a maximum voltage rating of 690V AC. The relay includes integrated bimetallic elements, eliminating the need for separate thermal units, and does not offer phase loss sensitivity.

Frequently Asked Questions

What is the SIEMENS 3RU21261JB0 overload relay used for?

The SIEMENS 3RU21261JB0 is an IEC thermal overload relay used to protect motors from overheating due to overload or phase loss. It is designed for industrial applications with SIRIUS contactors of Frame Size S0, providing reliable thermal protection via integrated bimetallic elements.

What are the specifications of the SIEMENS 3RU21261JB0 overload relay?

The SIEMENS 3RU21261JB0 is a thermal overload relay with Frame Size S0, 3 poles, 1NO/1NC auxiliary contacts, screw terminals, and a maximum voltage rating of 690V AC. It includes integrated bimetallic elements, so no separate thermal units are needed. It does not offer phase loss sensitivity.

Where to buy the SIEMENS 3RU21261JB0 overload relay worldwide?

You can source the SIEMENS 3RU21261JB0 overload relay worldwide through 3G Electric, a global industrial equipment distributor. We handle full logistics, customs clearance, and delivery to your location. Contact us for availability and lead time.

How to select the correct SIEMENS overload relay for a SIRIUS contactor?

To select the correct SIEMENS overload relay, match the frame size of the relay to the SIRIUS contactor—both must be Frame Size S0. Ensure the current setting range (7 A – 10 A for the 3RU21261JB0) covers the motor full-load current. Verify auxiliary contact form and terminal type meet your control circuit requirements.

Used in

Common applications for Siemens
District cooling plants — LME73 + RWF55 for condenser-water modulation
Inflight catering and food-processing steam boilers — LMG22 with SQN90 air-fuel cross-damper
Hospital steam-plant redundancy — LME41 with QRA2 UV flame detection for dual-fuel boilers
Semiconductor fab process heat — LME23 and SKP55 gas valves on hot-oil heater skids
Container-terminal reefer-deck heating — LMG22 retrofit onto legacy burner racks

Siemens Products

3G Electric supplies Siemens iec thermal overload relays. We supply genuine products with in-stock availability on common SKUs, technical documentation, commissioning support, and warranty service — worldwide.

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SIEMENS Overload Relay: Thermal Protection, 3 Poles, 1NO/1NC, Frame Size S00, 0.35 A – 0.5 A (MPN 3RU21160FB0). Key specifications — Brand: SIEMENS; Auxiliary Contact Form: 1NO/1NC; Compatible Contactor Series: SIRIUS; Terminal Connection Type: Screw Terminals; Frame Size: S00; Maximum Voltage Rating: 690V AC; Phase Loss Sensitivity: No; Thermal Units Required: None (Relay Includes Integrated Bimetallic Elements).
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SIEMENS Overload Relay: Thermal Protection, 3 Poles, 1NO/1NC, Frame Size S00, 0.35 A – 0.5 A (MPN 3RU21160FB0). Key specifications — Brand: SIEMENS; Auxiliary Contact Form: 1NO/1NC; Compatible Contactor Series: SIRIUS; Terminal Connection Type: Screw Terminals; Frame Size: S00; Maximum Voltage Rating: 690V AC; Phase Loss Sensitivity: No; Thermal Units Required: None (Relay Includes Integrated Bimetallic Elements).