Thermal relay for motor overload protection, suitable for coupling to a contactor. Adjustment range according to motor rated current.
Tell us the reference or key specification (current, power, gauge, size), quantity and city — a technical advisor sends your quote the same business day.
The thermal overload relay protects the motor against prolonged overcurrent through calibrated bimetal strips, per IEC 60947-4-1. It couples to the contactor, is set to the motor nameplate current, and its trip class (10 A, 10, 20 or 30) defines the maximum tripping time at 7.2 times the set current.
The thermal overload relay protects motors against sustained overcurrents that cause abnormal heating. At TECTUL it is quoted by adjustment range, contactor compatibility, motor rated current and required reset type. The actual lot data indicates a thermal relay that couples to the contactor and has an adjustment range according to motor rated current. Its difference versus a thermal-magnetic manual motor starter is clear: the thermal relay does not replace short-circuit protection in the power circuit; it normally acts on the contactor control circuit to stop the motor when it detects overload. The selection of thermal relays and motor starters is related to IEC 60947-4-1, which classifies switching and protection equipment for low-voltage motors.
We dispatch thermal overload relays to Bogotá, Medellín, Cali, Barranquilla and all of Colombia. Request a quote via WhatsApp with current and compatible contactor.
| Class | Tripping time at 7.2 × set current | Application |
|---|---|---|
| 10 A | 2 – 10 s | Light starting (pumps, small compressors) |
| 10 | 4 – 10 s | Normal starting — the most common class |
| 20 | 6 – 20 s | Heavy starting (high-inertia fans) |
| 30 | 9 – 30 s | Very heavy starting (mills, centrifuges) |
Times per IEC 60947-4-1. Differential relays add phase-loss sensitivity: the mechanism detects imbalance between bimetal strips and trips faster when one phase is lost.
It depends on current range, contactor compatibility and accessories. TECTUL quotes via WhatsApp with motor nameplate data and a photo of the panel.
The thermal relay detects overload and opens the contactor control circuit. The manual motor starter adds thermal-magnetic protection and can isolate the motor circuit.
It is coupled to the compatible contactor or wired in series with the motor, and its auxiliary contact is integrated into the control circuit to drop the coil.
It is adjusted according to the motor nameplate rated current and operating conditions. It must not be set randomly to avoid nuisance trips or lack of protection.
Not by itself. It must be coordinated with upstream magnetic protection, fuses or an appropriate circuit breaker.
Yes, depending on the model. Manual reset is usually preferred when an unexpected start can affect safety or the process.
To the motor nameplate current (not the contactor rating): the dial is set to the nameplate value and is only raised within the range if verified intermittent duty causes nuisance trips.
Yes when it is the differential type: the differential mechanism detects the imbalance between the three bimetal strips and trips faster when a phase is missing, before the motor overheats.
Class 20 or 30 per IEC 60947-4-1: they allow 6 to 20 s or 9 to 30 s at 7.2 times the set current, enough time to accelerate high-inertia loads without tripping on start.
Updated: July 22, 2026
