Thermal Overload Relay

A thermal overload relay protects a motor from overheating. It mounts on a contactor, measures the motor current through bimetal strips and opens the control circuit if the current stays too high for too long, for example when the motor is overloaded or loses a phase.

Where it is used

• DOL and star-delta motor starters
• Motor feeders in MCC panels
• Pump and fan control panels
• Machine panels in factories

How to choose

• Setting range that includes the motor full-load current.
• Matching contactor size for direct mounting.
• Trip class: class 10 for normal starting, class 20 or 30 for heavy starting loads.
• Reset mode: manual or automatic.
• Back-up protection by fuses or an MCCB for short circuits.

Why buy from Unique Quality Engineering

Since 2012 we have supplied genuine components from ABB, Schneider Electric, Siemens, Mitsubishi and Fuji Electric to panel builders, factories and contractors across Bangladesh. Our engineers help you choose the right rating and model, and we use the same parts in the panels we build ourselves.

Frequently asked questions

Does an overload relay protect against short circuit?

No. It protects against overload and phase loss. Short-circuit protection comes from fuses, an MCCB or an MPCB upstream.

How do I set an overload relay?

Set it to the full-load current on the motor nameplate. In a star-delta starter fitted in the phase lines, set it to about 58% of the full-load current.

Why does my overload relay keep tripping?

Common causes are a wrong setting, an overloaded or jammed machine, low voltage or a missing phase. Our engineers can help find the cause.

Need a price for thermal overload relays? Request a quotation with the rating and quantity, or call or WhatsApp +8801992-389515.