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RFN420420 – T/O RELAY 250-420A MAN-AUTO
Lovato RFN420420 is a three-pole Class 10A thermal motor protection relay with a 250–420 A adjustable operational current range, 690 V rated operational voltage and selectable manual or automatic reset for high-current industrial motor protection.
£406.14
Why Choose the Lovato RFN420420 Thermal Overload Relay?
The Lovato RFN420420 is a heavy-duty thermal motor protection relay designed to protect three-phase motors against sustained overload conditions in high-current industrial applications. As part of the Lovato RFN420 motor protection relay series, it combines a three-pole thermal release with an adjustable current range for dependable motor protection in demanding machinery and control systems.
The RFN420420 provides selectable manual or automatic resetting, allowing the reset method to be configured according to the requirements of the motor control system. Its Class 10A tripping characteristic, integrated test button and trip indicator support straightforward operation and maintenance, while one normally open and one normally closed auxiliary contact enable integration with control and signalling circuits.
With an adjustable operational current range of 250–420 A and a rated operational voltage of 690 V, the RFN420420 is designed for high-current three-phase motor applications. Its screw-mounted construction, IP20 frontal protection and robust M10 power terminals make it suitable for industrial switchgear, motor control panels and heavy machinery installations.
Key Advantages
- Heavy-duty thermal overload protection for three-phase motors.
- 250–420 A adjustable operational current range for high-current motor applications.
- Selectable manual or automatic reset to suit different control requirements.
- Class 10A tripping characteristic for defined motor overload protection.
- Integrated test button and trip indicator simplify testing and fault identification.
- Integrated 1 NO + 1 NC auxiliary contacts for control and signalling circuits.
Key Features
- Lovato RFN420 motor protection relay series.
- 250–420 A adjustable operational current range.
- Three-pole thermal release.
- 690 V rated operational voltage.
- 1000 V rated insulation voltage.
- Selectable manual or automatic reset mode.
- Class 10A tripping characteristic.
- Non-phase-failure and non-single-phase-sensitive operation.
- Integrated test button and trip indicator.
- 1 NO + 1 NC auxiliary contacts.
Reliable Motor Protection for Industrial Machinery
Thermal overload relays such as the Lovato RFN420420 protect electric motors by responding to sustained overcurrent conditions that can cause excessive heating and equipment damage. Its adjustable 250–420 A operating range allows the protection setting to be matched to the motor's full-load current, while the Class 10A tripping characteristic provides a defined thermal overload response.
The RFN420420 is designed for high-current motor circuits where phase failure sensitivity is not required. Its selectable manual or automatic reset, test button, trip indicator and auxiliary contacts provide flexible integration into industrial control systems, making it suitable for demanding motor control, machinery and switchgear applications.
Typical Applications
- High-current three-phase motor overload protection.
- Industrial motor control panels and switchgear.
- Large pumps, fans and ventilation equipment.
- Compressors and processing machinery.
- Conveyors and material handling systems.
- Heavy industrial machinery and automation systems.
Technical Specifications
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| Current Range | 250–420 A | |
|---|---|---|
| Device Type | Thermal Overload Relay | |
| Load Voltage | 690 V | |
| Monitored Supply | Single-phase | |
| Reset Type | Manual or automatic | |
| Monitoring Function | Temperature / thermistor | |
| Contacts | 1NO + 1NC | |
| IP Rating | IP20 | |
| HS Code | 85364900 | |
| Manufacturer | Lovato Electric | |
| Series | RFN420 | |
| Model | RFN420420 | |
| Product type | Thermal motor protection relay | |
| Number of poles | 3 | |
| Type of release | Thermal | |
| Operational current | 250–420 A | |
| Rated operational voltage | 690 V | |
| Rated insulation voltage Ui | 1000 V | |
| Operational frequency | 50–60 Hz | |
| Tripping class | 10A | |
| Reset mode | Manual or automatic | |
| Phase failure detection | No | |
| Test button | Yes | |
| Trip indicator | Yes | |
| Protection rating | IP20 frontal | |
| Overvoltage category | III | |
| Pollution degree | 3 | |
| gG protection fuse | 630 A | |
| aM protection fuse | 500 A | |
| K5 protection fuse | 800 A | |
| Auxiliary contacts | 1 NO + 1 NC | |
| Auxiliary rated insulation voltage Ui | 690 V | |
| Auxiliary rated impulse withstand voltage Uimp | 6 kV | |
| Auxiliary rated operational voltage | 690 V | |
| Conventional free-air thermal current Ith | 10 A | |
| Main terminal type | Screw and flat washer | |
| Main terminal screw | M10 | |
| Main terminal width | 25 mm | |
| Main terminal tightening torque | 35 Nm | |
| Auxiliary maximum conductor size | 2.5 mm² | |
| Auxiliary terminal tightening torque | 0.8–1 Nm | |
| Operating temperature | -25 to 60 °C | |
| Storage temperature | -50 to 70 °C | |
| Compensation temperature | -20 to 60 °C | |
| Maximum altitude | 3000 m | |
| Normal operating position | Vertical plane | |
| Permitted mounting position | ±30° | |
| Mounting type | Screw mounting | |
| Full-load current at 480 V | 420 A | |
| Full-load current at 600 V | 420 A | |
| Weight | 2460 g |
Frequently Asked Questions
What is the Lovato RFN420420 used for?
The Lovato RFN420420 is a three-pole thermal motor protection relay designed to protect compatible three-phase motors against sustained overload conditions.
What current range does the Lovato RFN420420 support?
The relay has an adjustable operational current range of 250–420 A.
Does the Lovato RFN420420 support automatic reset?
Yes. The RFN420420 supports manual or automatic resetting, allowing the reset mode to be selected according to the application.
Does the Lovato RFN420420 detect phase failure?
No. The RFN420420 is non-phase-failure and non-single-phase sensitive.
What is the rated operational voltage of the Lovato RFN420420?
The RFN420420 has a rated operational voltage of 690 V and a rated insulation voltage of 1000 V.
Trusted Motor Protection from Lovato Electric
Lovato Electric RFN420 thermal motor protection relays provide adjustable high-current overload protection for demanding three-phase motor control, industrial machinery and switchgear applications.
