Allen-Bradley to Siemens Contactor Cross-Reference Guide
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The Siemens equivalent of an Allen-Bradley 100-C series contactor is a Siemens SIRIUS 3RT2 series contactor matched by AC-3 amp rating and coil voltage. For example, an Allen-Bradley 100-C09 (9 A AC-3) cross-references to a Siemens 3RT2016 (S00 frame) or 3RT2023 (S0 frame), while a 100-C23 (23 A) cross-references to a Siemens 3RT2026. Both product lines are IEC contactors used for motor starting, and in most panels they can be interchanged as long as amp rating, coil voltage, and auxiliary contact configuration are matched.
Allen-Bradley 100-C to Siemens 3RT2 Cross-Reference Table
| Allen-Bradley 100-C | AC-3 Rating (400V) | Siemens SIRIUS Equivalent | Siemens Frame |
|---|---|---|---|
| 100-C09 | 9 A | 3RT2016 / 3RT2023 | S00 / S0 |
| 100-C12 | 12 A | 3RT2017 / 3RT2024 | S00 / S0 |
| 100-C16 | 16 A | 3RT2018 / 3RT2025 | S00 / S0 |
| 100-C23 | 23 A | 3RT2026 (25 A) | S0 |
| 100-C30 | 30 A | 3RT2027 (32 A) | S0 |
| 100-C37 | 37 A | 3RT2028 (38 A) | S0 |
When an exact amp rating does not exist in the other manufacturer's line, size up to the next available rating — never down. Always confirm the AC-3 rating for your motor voltage on the manufacturer datasheet before substituting.
Coil Voltage Codes: Allen-Bradley vs. Siemens
The most common cross-reference mistake is matching the frame size but not the coil voltage. Allen-Bradley encodes coil voltage as a letter code in the middle of the part number (for example, 100-C09D10 for a 110–120 V AC coil), while Siemens encodes it in the suffix (for example, 3RT2016-1AK60 for 110–120 V AC). Common Siemens coil suffixes: -1AB00 (24 V AC), -1BB40 (24 V DC), -1AK60 (110–120 V AC), -1AL20 (230 V AC). Verify the coil code on the side label of your existing contactor against the datasheet — a contactor with the wrong coil voltage will either not pull in at all or will burn out the coil.
Symptoms That Mean Your Contactor Needs Replacement
- Contactor won't pull in: No click when the control circuit energizes usually means an open coil, wrong coil voltage, or a failed control signal. Check coil resistance — an open reading confirms a dead coil.
- Chattering or buzzing: Rapid clicking or loud hum points to low control voltage, a worn shading coil, or dirt on the magnet pole faces. Chattering rapidly destroys the contacts and coil.
- Welded contacts / motor won't stop: If the motor keeps running after the stop command, the main contacts have welded — typically from switching a locked-rotor load or an undersized contactor. Replace immediately; this is a safety failure.
- Coil burnout / burnt smell: Overvoltage, chattering, or a jammed armature overheats the coil. On sealed IEC contactors, replace the complete contactor.
Compatibility Caveats Before You Swap
- Mounting footprint: DIN-rail mounting is standard on both lines, but panel-mount hole patterns differ between AB 100-C and Siemens 3RT2 — check depth and width in tight enclosures.
- Auxiliary contacts: An AB 100-C09x10 has 1 N.O. auxiliary built in; Siemens 3RT2 base units vary (some include 1 N.O. or 1 N.C.). Snap-on auxiliary blocks are not interchangeable between brands.
- Reversing pairs and overloads: Mechanical interlocks, reversing wiring kits, and overload relays (AB 193-E vs. Siemens 3RU2/3RB3) are brand-specific — replace as a set.
Frequently Asked Questions
Can I replace an Allen-Bradley contactor with a Siemens contactor?
Yes. Both are IEC-rated contactors. Match the AC-3 amp rating, coil voltage, and auxiliary contact arrangement, and verify the physical footprint fits your panel.
What is the Siemens equivalent of the Allen-Bradley 100-C09?
The Siemens 3RT2016 (S00 frame) or 3RT2023 (S0 frame), both rated 9 A AC-3 — matched with the correct coil voltage suffix.
Are surplus or used contactors reliable?
Yes, when tested. Contactors are electromechanical and easy to verify: coil resistance, contact continuity, and free armature movement. AIPG tests and grades every surplus unit before it ships.
Do discontinued Allen-Bradley contactors have replacements?
Older lines like the Bulletin 100-A cross to current 100-C or Siemens 3RT2 units by amp rating — or we can source the exact obsolete part number from surplus stock.
Shop Contactors at AIPG
American Industrial Parts Group stocks new, surplus, and used Allen-Bradley and Siemens contactors and motor starters — tested, graded, and ready to ship. Browse our Contactors & Motor Starters collection, or send a sourcing request if you need a specific part number.