Contactor Relay vs Contactor: What's the Difference & When to Use Each A contactor is built to switch a motor or heavy load directly, with contacts rated for the high inrush current a motor draws at start-up. A contactor relay looks almost identical and works on the same electromagnetic principle, but its contacts are only rated for small control-circuit currents — pilot lights, interposing signals, small solenoids — not for switching a motor's actual load current. Using one in place of the other, in either direction, either wastes money or risks welding the contacts closed the first time it switches a real motor load. Here's exactly what separates them, how to tell which one a datasheet is describing, and where each belongs in a control panel. Talk to Our Expert Team Same Mechanism, Different Contact Rating Both devices are electromagnetic switches — a coil pulls an armature to close a set of contacts, exactly like the mechanism inside any contactor. The entire difference is in what those contacts are built and tested to switch. A motor contactor's contacts are sized with an AC3 utilisation category rating for motor loads, meaning they're tested to make and break the high inrush current a motor draws at start-up without welding or excessive arcing. A contactor relay's contacts carry a much lower AC15 or general-purpose rating, sized for small control-circuit currents like indicator lamps, small solenoids, or signalling to a PLC input — not for a motor's starting current. Comparison of a motor contactor rated for high motor starting current against a contactor relay rated only for small control circuit currents Left: a contactor switching a motor's high inrush current with AC3-rated contacts. Right: a contactor relay switching a small pilot lamp or PLC input signal with much lighter-duty contacts. Contactor (AC3-rated) M High inrush current Coil Heavy-duty contacts — tested for motor starting Contactor Relay (AC15/GP) Small signal current Coil Light-duty contacts — not for motor loads Side-by-Side Comparison Feature Contactor Contactor Relay Contact ratingAC3 (motor loads) or AC1 (resistive)AC15 or general-purpose (control signals) Typical current9A to several hundred ATypically under 10A, control-circuit only Typical useSwitching motors, heaters, heavy loads directlyInterlocking, signalling, indicator lamps, PLC I/O Overload relay pairingAlmost always paired with one for motor protectionNot applicable — no motor load to protect Physical sizeLarger, scales with current ratingSmaller and more compact Common Places Each One Belongs in a Panel Application Correct Choice Why Switching a motor on/off directlyContactorOnly contactor contacts are rated for motor inrush current Interlocking two starters so only one runs at a timeContactor relayOnly switching low-current control signals, not the motors themselves Extending a contactor's auxiliary contacts for more signalling pointsContactor relayAdding indicator lamps or PLC feedback, not more load switching Switching a resistive heater load directlyContactorLoad current still exceeds a contactor relay's rating in most cases Frequently Asked Questions What happens if I use a contactor relay to switch a motor directly? Its contacts aren't rated for the motor's inrush current, so repeated switching will pit, arc, and eventually weld the contacts closed — leaving the motor unable to be switched off, which is a genuine safety hazard, not just a reliability problem. Is a "control relay" the same thing as a contactor relay? They're closely related terms often used interchangeably by manufacturers and suppliers — both describe a lighter-duty electromagnetic relay for control-circuit switching rather than motor loads. Some ranges specifically badge them "contactor relay" because they share the same physical footprint and coil options as the manufacturer's contactor line. Why would I choose a contactor relay over a standard control relay? Mainly for panel consistency — a contactor relay sharing the same physical range as the panel's contactors often shares accessories, mounting, and coil voltage options, simplifying spares holding and panel design compared with mixing in a completely different relay family. Can a contactor be used where a contactor relay would normally go? Technically yes — a contactor's higher-rated contacts will happily switch a small control-circuit load. It's not dangerous, just an oversized and more expensive choice than the job requires, and it typically takes up more panel space than needed. How do I confirm which one a datasheet is describing? Check the stated utilisation category — AC3 (or AC1 for resistive loads) indicates a load-switching contactor; AC15 or a "control relay"/"contactor relay" designation with no motor kW rating indicates control-circuit-only contacts. If a motor kW or AC3 current rating isn't listed at all, treat it as control-circuit rated only. Related Reading Why Is My Contactor Buzzing or Not Pulling In? → Contactor Procureme…