RELETEK RD-RT40 Panel Temperature Regulator Relay with NTC Sensor

The RELETEK RD-RT40 Panel Temperature Regulator Relay is a compact temperature control device designed to automatically regulate heating and temperature-dependent electrical loads. It uses an external RT811 NTC temperature sensor to measure the temperature at the required monitoring point and switches its relay output according to the selected temperature setting and hysteresis. This makes the RD-RT40 suitable for electrical panels, heating systems, ventilation equipment, and general industrial temperature-control applications.

The RD-RT40 uses a microcontroller-based control system and provides adjustable temperature and hysteresis settings through front-panel potentiometers. The temperature control range extends from -5°C to +40°C, while the hysteresis can be adjusted from approximately 0.5°C to 3°C. Adjustable hysteresis helps prevent excessive relay switching when the measured temperature fluctuates around the setpoint.

The controller accepts a wide 24–240V AC/DC supply, allowing it to be integrated into control panels with different supply voltages. Power consumption is approximately 1.5W, and the unit operates at 50/60Hz when supplied with AC. The temperature sensor is connected through dedicated measuring terminals T1 and T2.

For load switching, the RD-RT40 provides one changeover contact (1 C/O) rated at 16A/250V AC-1. The relay has a switching capacity of up to 4000VA on AC-1 loads and 300W for DC loads. For motors, compressors, heaters, or other loads with higher starting or inductive currents, an appropriately rated contactor should be used instead of connecting the load directly to the relay.

The supplied RT811 sensor uses an NTC sensing element and features a stainless-steel probe approximately 6mm in diameter and 50mm long. Its cable is 2 × 0.5mm² with a 2.5m length and uses high-temperature PVC insulation. The external probe allows the sensing point to be positioned away from the DIN-rail controller, which is useful when the temperature of a cabinet, room, pipe, equipment surface, or other controlled area needs to be monitored.

The controller provides LED indication for the power supply and relay state. Its compact 2-module DIN-rail housing is designed for TH-35 rail mounting, making it suitable for electrical distribution boards and automation panels. The controller itself has an IP20 protection rating, while the supplied external sensor is specified as IP65 by RELETEK documentation.

Features

• Microcontroller-based temperature regulation

• External RT811 NTC temperature sensor

• Adjustable temperature range of -5°C to +40°C

• Adjustable hysteresis from approximately 0.5°C to 3°C

• Wide 24–240V AC/DC power supply

• 1 C/O relay output

• Relay rating of 16A / 250V AC-1

• LED indication for power and relay status

• Compact 2-module DIN-rail housing

• TH-35 rail mounting

• 2.5m external temperature sensor cable

Specifications

Specifications are based primarily on the RELETEK manufacturer documentation.

Applications

• Electrical panel temperature control

• Heating system control

• Floor heating systems

• Ventilation and cooling systems

• HVAC control panels

• Electrical cabinet temperature monitoring

• Pump and fan temperature control

• Industrial automation systems

• Equipment temperature regulation

• General heating and cooling applications