Siemens 3RT2016-1BB42 — 24 V DC Contactor Buying Guide

By Abdullah Zahid
13 min read
Siemens 3RT2016-1BB42 size S00 power contactor with 24 V DC coil for three-phase motor control on DIN rail

Siemens 3RT2016-1BB42 Power Contactor: Specifications, Wiring, Selection Guide, and Honest Alternatives Review

If you have a model number in hand — whether from a maintenance ticket, an OEM panel schematic, or an RFQ — you are at the point where verification and sourcing matter more than browsing. The Siemens 3RT2016-1BB42 is a 3-pole, size S00 power contactor rated for 4 kW at 400 V under AC-3 duty, with a 24 V DC coil and one integrated normally closed auxiliary contact. It fits 35 mm DIN rail, draws 166.7 mA at nominal coil voltage, and is the standard choice in compact industrial panels where control power comes from a battery-backed or UPS-sourced 24 V DC supply.

If you have already confirmed this is the right part, check current pricing and availability at LeadTime.ca — ships worldwide.

Who Should Buy the 3RT2016-1BB42 — and Who Shouldn't

This contactor is the right choice when all five of the following conditions are true for your application:

  • Your control supply is 24 V DC — not 110 V AC, 230 V AC, or any AC voltage
  • Your load is at or below 4 kW at 400 V three-phase under continuous AC-3 duty (9 A switching current)
  • Your panel uses standard 35 mm DIN rail and the S00 footprint (45 mm wide) fits your layout
  • Screw terminals are acceptable — you are not specifying spring-loaded or push-in termination
  • You need exactly one normally closed auxiliary contact for feedback, interlocking, or pilot lamp control

If your load exceeds 5.5 kW, your control voltage is AC, or you need spring-loaded terminals, this is not the correct variant. The 3RT2016-2BB42 handles spring-loaded terminals with identical electrical specs, while the 3RT2018 series addresses higher power requirements. Scroll to the variant comparison section for specific part guidance.

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What the 3RT2016-1BB42 Actually Does in a Live System

The Siemens 3RT2016-1BB42 is the switching element between your control logic and a three-phase load. When your PLC digital output, safety relay, timer, or push-button circuit closes and energizes the 24 V DC coil at terminals A1 and A2, the three normally open main contacts close simultaneously, connecting line power to the motor or equipment load across terminals L1–L3 (input) and T1–T3 (output). When the coil is de-energized, a mechanical spring return opens all three main contacts within approximately 10 ms, disconnecting the load.

The single normally closed auxiliary contact — included as part of the standard 3RT2016-1BB42 configuration — provides a status signal back to your control system. When the contactor coil is de-energized and main contacts are open, this auxiliary contact is closed, giving the PLC or safety module a confirmed off-state signal. When the coil energizes and main contacts close, the auxiliary contact opens. This behavior is the basis for motor running confirmation, interlocking between forward and reverse starters, and redundancy checking in safety circuits.

Critically, this contactor includes no built-in circuit breaker, overload relay, or short-circuit protection. Per EN 60947-1, an external protection device — typically a thermal overload relay from the Siemens 3RU2 or 3RA2 series mounted in series — is mandatory for compliant motor protection installations. The contactor alone is a switching device, not a protective device.

Where the 3RT2016-1BB42 Sits in Your System Architecture

The 3RT2016-1BB42 lives in the middle of the motor control signal chain — downstream of the control logic and upstream of the motor load. Understanding this placement helps during commissioning, troubleshooting, and panel layout.

  • Control logic layer: PLC digital output, safety relay module, or hardwired push-button circuit generates the 24 V DC switching signal
  • Coil circuit: 24 V DC signal feeds terminals A1 and A2 on the contactor, with a flyback diode recommended across the coil to suppress voltage spikes on de-energization
  • Main power circuit: three-phase supply (up to 690 V line-to-line) feeds L1, L2, L3; load connects to T1, T2, T3 through an external thermal overload relay in series
  • Protection layer: thermal overload relay (e.g., Siemens 3RU2 series) mounted downstream of main contacts, set to motor full-load amperage
  • Feedback path: the 1 NC auxiliary contact wired back to PLC input or safety relay for running status confirmation and interlock logic

Industries and Applications That Specify This Contactor

The 3RT2016-1BB42 appears most frequently in compact motor control panels where panel real estate is limited and the 24 V DC control infrastructure is already in place. In manufacturing environments — textile mills, packaging lines, printing plants — the S00 footprint allows multiple motor starters to fit within a single enclosure section. The 4 kW AC-3 rating covers the majority of auxiliary and process motors in these environments: conveyor drives, feed rollers, indexing motors, and small compressors.

HVAC applications represent a consistent second market. Cooling tower pump starters, chiller loop circulator control, and rooftop unit fan contactors frequently specify 24 V DC coils because building automation systems and BMS controllers typically output 24 V DC switching signals. The 3RT2016-1BB42 interfaces directly to these outputs without an intermediate relay.

Water and wastewater treatment installations use this contactor for pump control duty, where the AC-3 switching profile — rated up to 750 cycles per hour — handles the frequent start/stop demands of level-controlled pumps. Food and beverage production lines use it for wash-down area motor starters, where the IP20 protection class requires additional enclosure-level protection but the contactor itself handles switching reliably in temperature ranges from -25 to +60°C.

Legacy panel upgrade projects are a significant volume driver for this exact part number. When existing DIN rail infrastructure and 24 V DC control wiring must be preserved, the 3RT2016-1BB42 is a direct footprint match for older Siemens 3TF46 series contactors, allowing replacement without panel re-wiring.

Application Typical Deployment
Three-phase motor starter (manufacturing) Conveyor, feed roller, or indexing motor up to 4 kW in compact MCC section
HVAC pump and fan control Chiller loop circulator or cooling tower fan, BMS 24 V DC output control
Water/wastewater pump control Level-controlled lift station or dosing pump, AC-3 frequent start/stop duty
Small machine main disconnect Drill press, band saw, or lathe controlled via safety relay module
Legacy panel upgrade Direct DIN rail replacement for 3TF46 series; preserves existing 24 V DC wiring
UPS-backed critical facility switching 24 V DC coil sourced from battery-backed supply for reliable operation during AC power events

Electrical Specifications Worth Verifying Before You Order

Specification Value
Main contacts 3-pole, 3 NO (normally open)
AC-3 rated power / current 4 kW at 400 V / 9 A switching current
Maximum operating voltage 690 V (line-to-line)
Operating current AC-1 (non-inductive) 22 A at 400 V, 40°C ambient
Thermal short-time current 72 A (10 s limited)
Coil voltage / power / current 24 V DC / 4 W / 166.7 mA
Coil resistance 144 Ohms
Auxiliary contact 1 NC (normally closed)
Dimensions (H x W x D) 58 mm x 45 mm x 73 mm
Operating temperature range -25 to +60°C

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

3RT2016-1BB42 vs. 3RT2016-2BB42 and When to Step Up in Size

The most common ordering confusion with this part involves the terminal type and the duty cycle rating. The table below covers the decision points engineers actually face at the ordering stage.

Model Terminal Type Coil Voltage AC-3 Rating AC-4 Rating Best For
3RT2016-1BB42 (this model) Screw terminal 24 V DC 4 kW / 9 A at 400 V 2 kW / 4.1 A at 400 V (approx. 200,000 cycles) Budget-optimized, standard panel builds, continuous motor duty
3RT2016-2BB42 Spring-loaded terminal 24 V DC 4 kW / 9 A at 400 V 2 kW / 4.1 A at 400 V High-volume panel assembly, repeated changeouts, no torque driver required
3RT2016-1AB41 Screw terminal 230 V AC 4 kW / 9 A at 400 V 2 kW / 4.1 A at 400 V Panels without 24 V DC supply; AC control circuit infrastructure
3RT2016-1AF41 Screw terminal 400 V AC 4 kW / 9 A at 400 V 2 kW / 4.1 A at 400 V Line-voltage control circuits; older industrial installations
3RT2018 series Screw or spring Multiple options 7.5 kW and above at 400 V Higher derating applies Loads above 5.5 kW; next size up from S00

If your panel is already wired with 24 V DC control and your load sits at or below 4 kW continuous AC-3 duty, the 3RT2016-1BB42 is the correct choice — check current availability at LeadTime.ca.

Expert Verdict: Honest Assessment for Engineers and Procurement

The Siemens 3RT2016-1BB42 earns its position as a workhorse item because the S00 form factor, 24 V DC coil, and AC-3 4 kW rating align with the most common motor control requirement in compact industrial panels worldwide. The coil draws only 4 W at 166.7 mA — well within the output capacity of virtually any 24 V DC control supply — and the operating temperature range of -25 to +60°C makes it viable from outdoor HVAC enclosures to temperature-controlled production environments. The mechanical life supporting approximately 200,000 operating cycles at AC-4 duty, and an operating frequency of up to 750 cycles per hour under AC-3, means this contactor will outlast many of the machines it controls when correctly specified and installed.

Where this contactor has real limits: the 4 kW AC-3 rating leaves essentially no headroom for motors at the upper edge of that range running in demanding duty cycles. If your application involves frequent jogging, reversing, or plugging, the AC-4 rating of 2 kW at 400 V applies — meaning a 3 kW motor in plugging duty exceeds the rated capacity of this contactor and will accelerate contact wear significantly. There is also no integrated protection; every installation requires a correctly sized thermal overload relay in series. Engineers who have inherited a panel and found a contactor tripping intermittently should check for overload relay sizing issues before assuming the contactor is at fault. For loads above 5.5 kW, do not attempt to run the 3RT2016-1BB42 at a higher current — move to the 3RT2018 series instead.

From a procurement standpoint, this is a commodity-tier item with broad distributor depth, meaning lead times are typically short and multi-source options exist. Buying one or two spare units for mission-critical motor starters is low-cost insurance against unplanned downtime. Volume pricing becomes relevant at ten or more units. If you are managing annual maintenance replacements across multiple facilities, a blanket order or supply agreement with a distributor that stocks this part regularly is worth negotiating. If this matches your system requirements, view current stock and pricing at LeadTime.ca.

For volume pricing or to confirm lead time before committing to a build, contact the LeadTime.ca team directly — we ship worldwide.

Wiring and Installation Overview

The following points cover the key requirements and checks for installing the 3RT2016-1BB42. For complete wiring diagrams and installation procedures, refer to the official Siemens SIRIUS 3RT2 series installation manual.

  • Main circuit: three-phase supply connects to terminals L1, L2, L3 (input); load feeds from T1, T2, T3 (output); a thermal overload relay in series downstream is required — not optional
  • Coil circuit: 24 V DC positive to terminal A1, negative (or common) to A2; a flyback diode (such as a 1N4007 or equivalent) across A1–A2 is strongly recommended to suppress inductive voltage spikes when the coil de-energizes
  • Auxiliary contact: the 1 NC contact is wired into the PLC input or safety relay feedback circuit; verify the contact is normally closed at rest (coil de-energized) using continuity mode on a multimeter before commissioning
  • Screw terminal torque: use a calibrated torque driver set to the manufacturer-specified torque for the M3.5 screw terminal; under-torqued connections are the leading cause of intermittent contact failure and thermal events in screw-terminal contactors
  • Panel mounting: snap onto 35 mm DIN rail per EN 60715; maintain minimum 6 mm clearance side-to-side for live parts; confirm conductor cross-section matches ambient temperature conditions before final termination

What Engineers Get Wrong When Ordering This Contactor

Four recurring errors account for the majority of wrong-part orders and post-installation failures with the 3RT2016-1BB42.

The most common is coil voltage mismatch. The 3RT2016-1BB42 is 24 V DC exclusively. Siemens produces 230 V AC (3RT2016-1AB41) and 400 V AC (3RT2016-1AF41) variants with nearly identical part numbers. Connecting the wrong coil voltage causes immediate failure or no operation. The suffix in the Siemens catalog number encodes the coil voltage: -1BB42 indicates 24 V DC; -1AB41 indicates 230 V AC. Always verify the suffix against your control circuit supply before ordering.

The second error is misapplying the AC-3 power rating to AC-4 duty. The 4 kW rating at 400 V applies specifically to AC-3 continuous motor switching duty. Under AC-4 plugging, reversing, or jogging duty, the rating drops to 2 kW at 400 V with a 4.1 A switching current. Running a 3 kW motor under jogging duty through a 3RT2016-1BB42 rated only for 2 kW at AC-4 will accelerate contact erosion and shorten service life well below the approximately 200,000 cycles mechanical life figure.

The third error is omitting the thermal overload relay entirely or sizing it incorrectly. The 3RT2016-1BB42 has no built-in motor protection. A thermal overload relay must be specified and installed in series. Setting the trip point too high fails to protect against locked-rotor conditions; setting it too low causes nuisance trips on motor inrush current during starting.

The fourth error is ordering the wrong terminal type after comparing part numbers. The 3RT2016-1BB42 uses screw terminals. The 3RT2016-2BB42 uses spring-loaded terminals. Both have identical electrical ratings. If your installation method, panel assembly process, or replacement policy specifies one terminal type, confirm the suffix before finalizing the purchase order.

Wrong-Part Prevention Checklist

Before placing your order, work through each item below. This checklist is drawn directly from the product verification data and covers the specific failure points for this model.

  1. Verify coil voltage is 24 V DC (check label on existing device; common error: confusing with 230 V AC variants)
  2. Confirm load is ≤4 kW at 400 V three-phase continuous duty (AC-3 rating); DO NOT use for DC motor circuits without derating
  3. Check main circuit voltage does not exceed 690 V (line-to-line)
  4. Confirm DIN rail mount is required; some older panels use direct panel mount (different part)
  5. Verify terminal type: screw terminals required (if spring-loaded needed, order 3RT2016-2BB42-1AA0 instead)
  6. Check auxiliary contact type: must be 1 NC for feedback loop; compare to 1 NO variants if different interlocking logic needed
  7. Ensure external protection device (contactor+overload relay combination or VFD front-end) is specified separately; 3RT2016-1BB42 itself has no built-in circuit breaker

If any item on this checklist does not match your application, contact the LeadTime.ca team to confirm the correct variant before ordering — or review the full product page for additional selection guidance.

Frequently Asked Questions

Can I use the 3RT2016-1BB42 for a 5 kW motor at 400 V?

No. The AC-3 rating for this contactor is 4 kW at 400 V, corresponding to a 9 A switching current. Applying it to a 5 kW motor exceeds the rated capacity and will accelerate contact erosion. For loads above 5.5 kW, the 3RT2018 series is the appropriate next step up in the SIRIUS 3RT family.

What is the difference between the 3RT2016-1BB42 and 3RT2016-2BB42?

Both models are electrically identical — 24 V DC coil, 4 kW at 400 V AC-3 rating, 1 NC auxiliary contact. The only difference is the terminal type: the 3RT2016-1BB42 uses screw terminals, and the 3RT2016-2BB42 uses spring-loaded terminals. The spring-loaded variant costs slightly more but eliminates the need for a torque driver and reduces installation time in high-volume panel builds.

Does the 3RT2016-1BB42 include motor overload protection?

No. This contactor has no built-in circuit breaker or thermal overload relay. Per EN 60947-1, an external protection device is required. A thermal overload relay from the Siemens 3RU2 or 3RA2 series should be specified and installed in series with the main contacts, with the trip point set to 110–120% of motor full-load amperage.

What coil current does the 3RT2016-1BB42 draw, and will it work with a standard PLC output?

The coil draws 166.7 mA at 24 V DC nominal, with a coil power of 4 W and coil resistance of 144 Ohms. Most PLC digital output cards rated for 24 V DC loads can drive this coil directly, but confirm that your specific output card's maximum current per channel (typically 0.5 A) exceeds 166.7 mA with margin. For outputs with lower current ratings or when driving multiple contactors, consider an intermediate relay or solid-state output module.

Is the 3RT2016-1BB42 a direct replacement for the older Siemens 3TF46 series?

The 3RT2016-1BB42 is the current-generation SIRIUS equivalent for legacy 3TF46 series contactors in the same power range. The S00 DIN rail footprint and 24 V DC coil voltage are consistent across generations. However, verify terminal labeling, auxiliary contact configuration, and exact mounting dimensions against your existing panel drawing before treating it as a confirmed drop-in replacement — minor mechanical differences may require adjustment.

What is the maximum operating frequency for the 3RT2016-1BB42 under AC-3 duty?

Under AC-3 duty, the 3RT2016-1BB42 supports a maximum operating frequency of 750 cycles per hour. This is the rated switching rate for motor control applications. For applications requiring higher switching rates, a solid-state contactor or soft starter is a more appropriate solution.

Why Order From LeadTime.ca

  • LeadTime.ca ships worldwide — no regional restriction on orders regardless of your facility location
  • Specializes in sourcing industrial automation parts including hard-to-find variants and discontinued models in the SIRIUS 3RT family
  • Volume pricing available for multi-unit orders — contact the team directly for blanket order or maintenance contract pricing
  • Fast response on availability confirmation before you commit a PO to a build schedule
  • View the 3RT2016-1BB42 product page for current pricing and stock status
  • Contact LeadTime.ca for volume quotes, lead time verification, or sourcing assistance

At-a-Glance Summary

  • Model: Siemens 3RT2016-1BB42 — 3-pole, size S00 power contactor in the SIRIUS 3RT2 family
  • AC-3 rating: 4 kW at 400 V, 9 A switching current; maximum operating voltage 690 V
  • AC-4 rating: 2 kW at 400 V, 4.1 A — approximately 200,000 mechanical operating cycles
  • Coil: 24 V DC, 4 W, 166.7 mA, 144 Ohms resistance — compatible with standard PLC 24 V DC outputs
  • Operating current AC-1 (non-inductive): 22 A at 400 V, 40°C ambient; thermal short-time current 72 A (10 s)
  • Auxiliary contact: 1 NC included — for motor running feedback, interlocking, or safety circuit integration
  • Dimensions: 58 mm H x 45 mm W x 73 mm D; mounts on 35 mm DIN rail per EN 60715
  • Operating temperature: -25 to +60°C; protection class IP20
  • No built-in circuit breaker — external thermal overload relay required per EN 60947-1
  • Key variant: 3RT2016-2BB42 for spring-loaded terminals with identical electrical specs
  • Operating frequency AC-3: maximum 750 cycles per hour