Siemens3RN1062-1CW00PTC Thermistor Motor Protection Relay, 6 Sensor Circuits, Multi-Motor, 1 NO + 1 NC, 45 mm DIN Rail

Product Description

What this part is

A Siemens SIRIUS 3RN1 thermistor motor protection relay, an evaluation unit for PTC temperature sensors embedded in motor windings. It monitors six independent sensor circuits, which is what makes it a multi-motor device: one relay watches the windings of several machines, or several separately sensed windings of one large machine. Winding temperature is read directly from the sensor chain rather than inferred from line current, so the relay responds to blocked cooling, high ambient temperature and frequent starting as readily as to sustained overload.

Decoding the order code

3RN1 is the SIRIUS thermistor motor protection family. The 06 block marks the six-sensor-circuit multi-motor evaluation unit, which is why this variant occupies the wider 45 mm enclosure rather than the 22.5 mm standard frame used by the single-circuit 3RN1010 and 3RN1013. 1C is the screw terminal connection method. W is the wide-range control supply, 24 to 240 V AC or DC on one terminal pair. The closing 00 is the variant index.

What these specs mean in practice

PTC sensing and current sensing answer different questions. A current-based overload relay sees the electrical symptom and has to model the thermal one; a PTC evaluation unit reads the winding itself, which is the quantity that actually destroys insulation. The trade-off is that this relay offers no protection against short circuit or locked-rotor current as such, and no current measurement at all, so it sits alongside a motor starter protector or fuses rather than replacing them. Sensor chains follow DIN 44081 and DIN 44082 PTC characteristics; the evaluation trips as the chain resistance rises through the high-resistance region and releases again once the winding has cooled and resistance falls back. Six circuits, evaluated separately with an LED per circuit, means a trip points at the machine that caused it instead of at the group.

Output and reset behaviour

The output is one normally-open and one normally-closed contact, taken to the contactor coil circuit and to a fault indication respectively. Reset is selectable as automatic, manual at the front button, or remote through a wired input, which is the difference between a machine that restarts itself on cooling and one that requires an operator to attend. Galvanic isolation separates the sensor circuits from the supply and contact circuits. Eight front LEDs cover ready and tripped state plus the individual sensor circuits, and the front button doubles as a test.

Quantity and configuration

1 Pc. Evaluation relay only. No PTC sensors, no sensor cable, no DIN rail, no remote reset pushbutton and no contactor.

Installation and setup notes

The unit is a 45 mm wide DIN rail device with screw terminals. The sensor chain is wired as a series loop from the motor terminal box, kept clear of power cabling to avoid induced interference, and the control supply accepts anything from 24 to 240 V, AC or DC, at 50 or 60 Hz. The relay carries ATEX approval for the thermal protection of motors in increased-safety service, which is the application where PTC evaluation is mandatory rather than optional.

Interchange guidance

The 3RN1 range is superseded by the SIRIUS 3RN2 series, and the 3RN2 six-circuit multi-motor evaluation unit is the current-catalogue equivalent, with different terminal layout and mounting width. Within 3RN1, the 3RN1010 and 3RN1013 are single-sensor-circuit 22.5 mm units and are a different device rather than a smaller version of this one. Variants differing in the supply-voltage letter or in the 1B spring-terminal connection code are the same function with a different supply range or wiring method.