Contactor and Relay Terminal Markings
Identify common IEC contactor coil, power, auxiliary-contact, and overload terminal markings, with device-specific limits and contact examples.
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Terminal lookup
The following are common IEC-style markings found on ABB contactors, auxiliary contacts, and overload relays. They identify terminal functions within the applicable product family. They are not a universal numbering system for every relay or controller.
| Marking | Typical function | Important distinction |
|---|---|---|
| A1, A2 | Operating coil terminals | Read the coil voltage/frequency and polarity markings where applicable. The coil rating is separate from the main power circuit. |
| 1/L1, 3/L2, 5/L3 | Main circuit line-side terminals | Follow the exact product diagram and any direction-of-feed restrictions. |
| 2/T1, 4/T2, 6/T3 | Corresponding main circuit load-side terminals | Terminal numbers do not establish phase sequence or connected motor rotation. |
| 13–14 | Normally open auxiliary contact | A low-current control contact, not another main power pole. Verify its utilization rating. |
| 21–22 | Normally closed auxiliary contact | Contact state is referenced to the device’s defined normal condition. |
| 33–34 / 43–44 | Additional normally open auxiliary contacts on applicable blocks | Use the block schematic to establish which pairs exist. |
| 11–12–14 | A common changeover contact pattern: common, NC, NO | Applies only where the device diagram uses this numbering; not the same arrangement as a 13–14 NO pair. |
| 95–96 | Common overload relay trip contact, normally closed before trip | Overload state and reset status determine operation; verify the relay instructions. |
| 97–98 | Common overload relay trip indication contact, normally open before trip | Do not assume every overload relay provides this pair. |
| PE / protective-earth symbol | Protective bonding terminal where marked | Not a coil return or a general-purpose signal reference. |
Read the contact state
For an ordinary non-latching contactor, the drawing generally shows contacts with the coil de-energized. A normally open auxiliary closes when the contactor operates; a normally closed auxiliary opens. A trip contact instead relates to the relay’s defined untripped/tripped condition.
A latching relay, maintained actuator, or special function block needs its own definition of normal state. Contact numbers and a NO/NC label do not establish safety integrity, positive opening, or suitability for a safety circuit.
As a reading example, a coil marked A1/A2 and an auxiliary pair marked 13/14 represent different functions. Do not connect power to a terminal pair merely because its number appears in this chart.
Check the actual assembly
- Record the complete device catalog number, coil code, and installed auxiliary or overload blocks.
- Locate the terminal diagram supplied with those exact parts. Add-on blocks can change which numbers are available.
- Check control voltage, AC/DC requirements, polarity where marked, contact ratings, conductor range, and connection instructions.
- Compare the diagram with the project control drawing. Record discrepancies before replacement or testing.
Use the schematic symbol legend to distinguish the drawn contact and coil. Keep observed markings and test conditions in an electrical test record.