Siemens 3RT2026-1BB40 — 11kW 25A Contactor Selection Guide

By Abdullah Zahid
16 min read
Siemens 3RT2026-1BB40 SIRIUS S0 frame 3-pole 24V DC coil power contactor for industrial motor control

Siemens 3RT2026-1BB40 SIRIUS Power Contactor: 11 kW at 400V Specifications, Selection Guide and Alternatives

Controls engineers and procurement teams searching for the Siemens 3RT2026-1BB40 contactor are typically at one of two points: verifying a direct replacement for a failed unit, or specifying a new motor control circuit that needs a 24V DC coil, 3-pole, 11 kW IEC-rated switch in a compact S0 frame. This is a SIRIUS family power contactor rated 25A at 400V AC-3 duty, with an integrated 1NO + 1NC auxiliary contact block and screw terminal connections — a combination that covers a wide range of industrial motor switching applications without requiring add-on feedback relays. If you have already confirmed this is the correct part for your system, check current pricing and availability for the 3RT2026-1BB40 at LeadTime.ca — ships worldwide.

Is the 3RT2026-1BB40 the Right Contactor for Your Application?

This contactor is the right choice for engineers and technicians who need all of the following confirmed before ordering:

  • Motor or load switching capacity up to 11 kW at 400V AC-3 duty — or up to 11 kW at 500V or 690V with derated current
  • Control coil voltage is 24V DC — sourced from a PLC output, relay logic circuit, or dedicated 24V DC control panel supply
  • Three-phase AC load switching — this is a 3-pole device and is not suitable for single-phase or DC load switching
  • IEC 60947-4-1 compliance is required for the motor circuit protection standard
  • Screw terminal wiring — the physical panel wiring practice must match screw-type terminations, not push-in or plug-in connectors
  • Status feedback via 1NO + 1NC auxiliary contacts is sufficient for the control system's PLC input and interlock logic

If your motor exceeds 11 kW at operating voltage, or if you need a coil voltage other than 24V DC, this is not the correct variant. The 3RT2028-1BB40 handles 40A and 18.5 kW in the same coil voltage, and multiple 3RT2026 series variants cover 110V AC and 230V AC coil voltages — see the variant comparison table below.

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What the 3RT2026-1BB40 Actually Does in a Motor Control System

The Siemens 3RT2026-1BB40 is a SIRIUS series electromechanical power contactor — an electromagnetically operated switch that connects and disconnects three-phase AC power circuits under load, on command from a low-voltage control signal. When a 24V DC signal is applied to the A1 and A2 coil terminals, the coil generates a magnetic field that pulls in the armature, closing three main power contacts simultaneously. Remove the signal, and a return spring opens the contacts, interrupting the load circuit. This all happens in milliseconds, and the design is rated for up to 10 million mechanical operating cycles under typical service conditions.

The practical role in a motor control circuit is straightforward: a PLC digital output, pushbutton circuit, or safety relay provides the 24V DC coil signal; the 3RT2026-1BB40 switches the 400V three-phase motor supply on and off. The integrated 1NO + 1NC auxiliary contact block provides immediate feedback — the normally-open auxiliary (terminals 13-14) closes when the coil is energized, confirming to the PLC that the contactor has pulled in and the motor supply is active. The normally-closed auxiliary (terminals 21-22) opens on coil energization, enabling interlock logic or alarm indication without an external status relay. This combination eliminates an entire relay module from the panel BOM in most standard motor control applications.

The S0 frame size keeps the footprint compact — important in dense control panels where DIN rail space is metered carefully. The insulation voltage is rated at 690V, the impulse voltage withstand is 6 kV, and the operating temperature range runs from -25 to +60°C, covering most indoor and light industrial enclosure environments.

Typical System Architecture: Where This Contactor Sits in the Circuit

The 3RT2026-1BB40 sits between the motor branch circuit protection device and the motor terminal box, acting as the remotely operated disconnect in the power path. Here is the typical component chain from controller to load:

  • PLC or control panel 24V DC output — provides the coil signal to A1/A2 terminals, often routed through a pushbutton or safety relay contact for manual override or emergency stop compliance
  • 3RT2026-1BB40 contactor — closes main power contacts (L1-L2-L3 in, terminals 2-4-6 out) on coil energization; auxiliary contact block feeds status back to PLC digital input
  • Thermal overload relay (separate device, sized to motor FLA) — wired in series on the output side of the contactor main contacts; trips the coil circuit on sustained overcurrent
  • Motor terminal box — receives switched three-phase supply from the contactor/overload relay combination
  • Optional: electronic soft-starter or bypass contactor wired downstream, with the 3RT2026-1BB40 serving as the main line contactor for initial connection

Industries and Use Cases Where the 3RT2026-1BB40 Is the Standard Choice

In CNC machine tools and metal fabrication environments, the 3RT2026-1BB40 is a common choice for spindle motor control and coolant pump switching. Modern machine tool controls run on 24V DC logic throughout, making the 24V DC coil a direct match for PLC output cards. Multiple units are often deployed on a single machine — one per motor axis or auxiliary drive.

HVAC and refrigeration panels use this contactor for compressor motor switching and condenser fan control. The frequent on-off cycling typical of HVAC duty — which aligns directly with AC-3 rating — combined with the S0 compact frame that fits tight panel spaces make this a practical fit. The 750 operations per hour maximum switching frequency at AC-3 is well above typical HVAC cycling rates.

Industrial conveyors and drive systems use the 3RT2026-1BB40 for motor on-off control and, in pairs, for reversing contactor circuits where two units are interlocked for forward and reverse motor direction. The 10 million mechanical cycle life rating supports the high-cycle demands of automated conveyor lines where the motor may start and stop hundreds of times per shift.

Water treatment and pumping installations use this contactor for submersible pump starters and duty cycle monitoring via the auxiliary contact feedback to SCADA inputs. The 690V insulation rating supports operation on higher voltage pump motors where applicable.

Application Typical Deployment
CNC Machine Tool Spindle and coolant pump motor switching via PLC 24V DC output; multiple units per machine
HVAC Compressor Control Compressor and condenser fan motor on-off; high-cycle AC-3 duty in compact panel space
Industrial Conveyor Drive Motor start-stop and reversing pair for direction change; paired with thermal overload relay
Water Treatment Pump Station Submersible pump starter with auxiliary contact feedback to SCADA/PLC digital input
Packaging Machinery Multi-motor control cells; soft-start bypass contactor configuration for smooth ramp
Safety Circuit Main Disconnect Main disconnect triggered by safety relay logic on emergency stop events

Key Specifications Every Engineer Needs Before Ordering

Specification Value
Frame Size S0
Number of Poles (Main) 3
Rated Current AC-3 at 400V 25A
Rated Power AC-3 at 400V 11 kW
Rated Power AC-3 at 690V 11 kW (13A)
Control Coil Voltage 24V DC
Minimum Coil Operate Voltage 19.2V DC
Auxiliary Contact Configuration 1NO + 1NC (6A at 24V DC)
Mechanical Operating Cycles 10,000,000 cycles
Operating Temperature Range -25 to +60°C

Full technical specifications are available on the product page at LeadTime.ca.

3RT2026-1BB40 vs 3RT2025 vs 3RT2028: Which Frame and Rating Do You Need?

Model AC-3 Current at 400V AC-3 Power at 400V Coil Voltage Frame Best For
3RT2025-1BB40 17A 7.5 kW 24V DC S0 Smaller motors up to 7.5 kW; lower cost where load permits
3RT2026-1BB40 25A 11 kW 24V DC S0 11 kW motor control with 24V DC PLC or relay logic
3RT2028-1BB40 40A 18.5 kW 24V DC Larger Motors up to 18.5 kW; higher panel space requirement
3RT2026-1AP00 25A 11 kW 230V AC S0 Same load rating where control system uses 230V AC coil
3RT2026-1AF00 25A 11 kW 110V AC S0 Legacy panels or systems with 110V AC control voltage

If your control architecture runs on 24V DC and your motor is rated at or below 11 kW at the operating voltage, the 3RT2026-1BB40 is the correct choice — check current availability and pricing at LeadTime.ca.

Expert Verdict: Where This Contactor Excels and Where It Has Real Limits

The 3RT2026-1BB40 earns its place as a staple in industrial motor control panels because it covers the single most common 3-phase motor size in light-to-medium industrial applications — the 11 kW range at 400V — with a 24V DC coil that maps directly onto modern PLC output cards without an intermediate relay stage. The 10 million mechanical cycle life rating is a meaningful reliability proof point: at 1,000 switching events per month, that works out to over 8 years of service before the mechanical mechanism approaches statistical end-of-life. The integrated 1NO + 1NC auxiliary block is not a marketing checkbox — it eliminates a discrete feedback relay from the panel, saving DIN rail space and one more device to procure and fail. For controls engineers building standard motor control circuits, this combination of ratings, coil voltage, and auxiliary configuration removes most of the selection ambiguity.

The honest limits are equally important to state. The 3RT2026-1BB40 provides no motor overload protection on its own — a thermal overload relay sized to the motor's full-load current is a mandatory addition, not optional. The auxiliary contacts are rated at 6A at 24V DC; they are for status signals and interlock logic only and must not carry motor load current or any current approaching that rating from inductive loads. The AC-3 rating of 25A at 400V is specifically for squirrel-cage motor switching; if the application involves plugging duty, jogging, or capacitive load switching, the AC-4 rating of 7.5 kW applies — a meaningful derating that catches engineers who read only the AC-3 line. Operating temperature is capped at 60°C ambient; installations in high-ambient enclosures without adequate ventilation will shorten coil insulation life. And if the motor exceeds 11 kW at the operating voltage, stop here and specify the 3RT2028-1BB40 instead.

From a procurement standpoint, the 3RT2026-1BB40 is a well-stocked catalog item at industrial distributors globally. Typical distributor lead times run 2 to 5 business days for standard orders, with emergency same-day or next-day availability at larger stocking locations. International orders may extend to 4 to 8 weeks depending on region and stock position — contact LeadTime.ca for a real-time lead time confirmation before committing to a build schedule. Volume pricing is available for multi-unit orders, which is relevant for OEM machine builders specifying the same contactor across multiple motor circuits. If this contactor matches your system requirements, view current stock and pricing at LeadTime.ca.

For volume pricing, lead time confirmation, or help selecting the correct variant before submitting a PO, contact the LeadTime.ca team directly — we ship worldwide.

Wiring and Installation Overview

The 3RT2026-1BB40 uses screw terminal connections throughout. The following points cover the key requirements before installation — always refer to the Siemens SIRIUS 3RT2026 series datasheet and applicable electrical codes for full wiring procedures and torque specifications.

  • Main circuit terminals accept wire in the 16-12 AWG range for single conductors, or 14-8 AWG for dual-strand configurations — use ferrules on stranded wire to prevent spreading under the screw clamp
  • Auxiliary contact terminals accept 0.5 to 1.5 mm² single conductors or 0.75 to 2.5 mm² dual-strand, sized for the 6A at 24V DC auxiliary circuit rating
  • Coil terminals A1 (positive 24V DC) and A2 (negative/return) should include a flyback diode or suppressor on the coil circuit to protect PLC outputs from inductive voltage spikes when the coil de-energizes
  • The minimum coil operate voltage is 19.2V DC — verify the 24V DC supply voltage at the contactor terminals under load conditions, accounting for any voltage drop across long control cable runs or undersized wire
  • Mount on standard DIN rail in the S0 frame orientation specified in the datasheet; confirm enclosure ambient temperature does not exceed 60°C at the mounting location

AC-3 vs AC-1 vs AC-4: Choosing the Right Duty Cycle Rating

The 3RT2026-1BB40 is rated and selected under AC-3 duty, which covers the most common industrial motor control scenario: starting a squirrel-cage induction motor and switching it off during normal running. At 400V AC-3, the rating is 25A and 11 kW. This is the number that governs selection for standard motor on-off control.

AC-1 is the non-inductive or mildly inductive load rating — heating elements, resistive loads, and similar. At 400V AC-1, the same contactor can switch 40A and 23 kW. This higher number is frequently misread as the motor control rating; it is not. Using AC-1 figures to size a contactor for motor switching leads to premature wear and contact failure because motor inrush current at starting creates far higher electrical stress on the contacts than a resistive load at the same current level.

AC-4 applies to plugging duty — reversing the motor while it is still running, or jogging. At 400V AC-4, the 3RT2026-1BB40 is rated at 7.5 kW. If your application involves frequent plugging or jogging cycles, either select the 3RT2026-1BB40 knowing the 7.5 kW AC-4 limit applies, or size up to the 3RT2028 series if the motor exceeds that threshold under jogging conditions.

Understanding the 1NO + 1NC Auxiliary Contact Configuration

The auxiliary contact block integrated into the 3RT2026-1BB40 provides two contacts with dedicated functions in most motor control circuits:

The normally-open (NO) contact at terminals 13 and 14 is open when the coil is de-energized and closes when the coil pulls in. The standard application is wiring this contact in series with a PLC digital input to provide a motor-running confirmation signal. The PLC sees a 24V DC high signal on that input only when the contactor has physically closed — a hardware confirmation that goes beyond trusting the PLC's own output state.

The normally-closed (NC) contact at terminals 21 and 22 is closed when the coil is de-energized and opens when the coil energizes. This contact is typically used for interlocking logic — for example, in a reversing contactor pair where energizing the forward contactor opens the NC contact in the reverse contactor's coil circuit, preventing simultaneous closure of both contactors and a phase-to-phase short circuit. It is also used for alarm indication when the motor is not running.

Both auxiliary contacts are rated 6A at 24V DC and 3A at 110V DC. These contacts are strictly for low-current control circuits and PLC inputs. They must not be used to switch motor loads or any load approaching the 6A limit from inductive devices, as this will drastically shorten contact life.

Pairing with a Thermal Overload Relay: What You Must Not Skip

The 3RT2026-1BB40 provides no built-in motor overload protection. It is a switching device, not a protective device. A thermal overload relay must be installed in series with the three main output terminals (2, 4, 6) on the motor side of the contactor. The thermal relay monitors motor current continuously and trips its own contact — which is wired into the contactor coil circuit — if sustained overcurrent is detected, de-energizing the coil and opening the main contacts before the motor winding temperature reaches a damaging level.

Size the thermal overload relay trip point to the motor's full-load ampere (FLA) rating from the motor nameplate. The trip point is typically set 5 to 10 percent above the motor FLA to allow for normal operating current variations without nuisance tripping, while still responding to genuine overload conditions. The thermal relay must be sized independently of the contactor current rating — a 25A contactor does not mean a 25A overload setting is correct; the motor nameplate FLA governs the relay setting.

Troubleshooting the Most Common 3RT2026-1BB40 Faults

Contactor Will Not Engage — Coil Not Pulling In

Measure DC voltage directly at terminals A1 and A2 with the control circuit active. The minimum operate voltage is 19.2V DC per the datasheet. If voltage is below this threshold, the coil will not pull in reliably — check for voltage drop across control wiring, verify the 24V DC supply under load, and confirm the PLC output or pushbutton contact is actually closing the coil circuit. If coil voltage is present and correct, disconnect power and measure coil resistance between A1 and A2. A reading of zero ohms indicates an internal coil short; an open circuit (infinite resistance) indicates a broken coil winding — both require unit replacement.

Contactor Chatters or Vibrates During Operation

Chattering is almost always a coil voltage issue — the supply is at or just above the minimum operate threshold during a brownout or voltage sag condition, causing the armature to repeatedly release and pull in. Verify that the 24V DC supply voltage is stable and does not sag below 19.2V DC during operation. A separate, dedicated 24V DC power supply for the contactor coil circuit isolates it from PLC output loading. If coil voltage is confirmed stable, inspect the main contact faces for oxidation or pitting, which can cause intermittent electrical contact and contribute to circuit instability.

Auxiliary Contact Provides No Feedback Signal to PLC

With the coil energized, test continuity between terminals 13 and 14 (NO contact) using a multimeter. If continuity is absent with the coil energized, the internal auxiliary contact has failed — replace the unit. If continuity is present but the PLC input is not registering the signal, check the 24V DC source connected to the auxiliary circuit, verify the wire from terminal 14 to the PLC input is intact, and confirm the PLC input impedance is within the range that the 6A-rated contact can drive reliably.

Motor Trips Thermal Overload Under Normal Running Conditions

First confirm the thermal overload relay trip dial is set to the correct value matching the motor nameplate FLA — a setting too close to or below the actual running current will cause nuisance trips. Next, check the three main contact faces of the 3RT2026-1BB40 for pitting or partial contact that could be creating a voltage drop and increasing effective current draw on the affected phase. Use a clamp meter on all three phases to check for current imbalance, which can indicate a failing contact or a phase loss condition upstream.

Wrong-Part Prevention: 8 Checks Before You Submit the PO

Before ordering the 3RT2026-1BB40, run through this checklist drawn from the most common specification errors on this part number:

  1. Verify control coil voltage is 24V DC (not 110V AC, 230V AC, or other variants)
  2. Confirm application is AC motor control (not DC load switching, which requires different model)
  3. Check load power does not exceed 11 kW at operating voltage (400V, 500V, or 690V)
  4. Ensure contactor frame (S0) fits available panel space; compare footprint against 3RT2025-1BB40 (smaller) or 3RT2028-1BB40 (larger)
  5. Verify auxiliary contact requirement (1NO + 1NC matches system feedback wiring)
  6. Confirm screw terminal connection matches field wiring practices (not plug-in)
  7. Check operating temperature range (-25 to 60°C) suits installation environment
  8. Validate incoming voltage supply is 3-phase AC (not single-phase); 3-pole design is for 3-phase only

If any of these checks flag a mismatch, contact the LeadTime.ca team before ordering — we can confirm the correct variant or alternative from the SIRIUS contactor range and check stock availability worldwide.

Frequently Asked Questions

What is the minimum coil voltage the 3RT2026-1BB40 will reliably operate at?

The minimum operate voltage for the 3RT2026-1BB40 coil is 19.2V DC. Below this threshold the contactor may fail to pull in fully or may chatter. This is a critical value to verify at the contactor terminals under actual operating conditions, not just at the power supply output — long control cable runs or undersized wire can drop the voltage at the terminal below the minimum even when the supply reads 24V DC at the source.

Does the 3RT2026-1BB40 include motor overload protection?

No. The 3RT2026-1BB40 is a switching contactor only and provides no motor overload protection. A separate thermal overload relay, sized to the motor's full-load ampere rating from the nameplate, must be installed in series with the contactor output terminals. The overload relay's trip contact is wired into the coil circuit to de-energize the contactor on an overload condition.

Can the 3RT2026-1BB40 be used for DC load switching?

No. This contactor is rated for AC motor control applications under IEC 60947-4-1 AC duty classifications. DC load switching has different arc interruption requirements and typically requires contactors specifically rated and designed for DC switching. Using an AC-rated contactor on DC loads can result in sustained arcing and contact failure.

What wire sizes are compatible with the screw terminals on the 3RT2026-1BB40?

The main circuit screw terminals accept 16 to 12 AWG single conductors or 14 to 8 AWG for dual-strand configurations. The auxiliary contact terminals accept 0.5 to 1.5 mm² single conductors or 0.75 to 2.5 mm² dual-strand. Use ferrules on stranded conductors to ensure a reliable screw terminal connection and prevent wire spreading under the clamp.

What is the switching frequency limit for the 3RT2026-1BB40 in AC-3 duty?

The maximum operating frequency in AC-3 duty is 750 operations per hour. This covers virtually all standard industrial motor control applications including HVAC compressor cycling and conveyor drive start-stop. Applications requiring switching frequencies above this rate should be evaluated against the AC-4 jogging duty rating, which applies different wear factors to the contact life calculation.

How do I confirm I am ordering the correct model number and not a common variant?

The official catalog number is 3RT2026-1BB40 — confirm the exact hyphenation and suffix. Common ordering errors include 3RT2026-1B40 (missing the second B in the coil voltage suffix) and incorrect suffix digits that correspond to different coil voltages or terminal configurations. Always verify the model number against the distributor datasheet before submitting the purchase order, and confirm the coil voltage code BB40 corresponds to 24V DC in the Siemens catalog suffix system.

Why Source the 3RT2026-1BB40 Through LeadTime.ca

  • Ships worldwide — no geographic restrictions on orders; international lead time confirmation available before you commit
  • Real-time stock and pricing visibility for the 3RT2026-1BB40 and related SIRIUS family variants including thermal overload relays and auxiliary contact blocks
  • Volume pricing available for OEM and MRO bulk orders — contact the team directly for project-based quotes
  • Sourcing support for hard-to-find or discontinued variants across the SIRIUS contactor range
  • Fast response for emergency replacement requests where production downtime cost is high

At-a-Glance Summary

  • Model: Siemens 3RT2026-1BB40 — SIRIUS 3-pole power contactor, S0 frame
  • Rated current: 25A at 400V AC-3 duty; 13A at 690V AC-3; 18A at 500V AC-3
  • Rated power: 11 kW at 400V, 500V, and 690V AC-3
  • Control coil: 24V DC; minimum operate voltage 19.2V DC
  • Auxiliary contacts: 1NO + 1NC, rated 6A at 24V DC and 3A at 110V DC
  • Mechanical life: 10,000,000 operating cycles typical
  • Maximum switching frequency: 750 operations per hour at AC-3
  • Insulation voltage: 690V; impulse withstand: 6 kV
  • Operating temperature: -25 to +60°C
  • Terminal type: Screw; main circuit 16-12 AWG; auxiliary 0.5-1.5 mm²
  • Compliance: IEC 60947-4-1; RoHS 2
  • Motor overload protection: NOT included — requires separate thermal overload relay
  • Available for worldwide shipment through LeadTime.ca