Watlow Series L Temperature Limiting Controller

(2) DIN rail installation (LF series)

Rail preparation: Confirm that the DIN rail complies with DIN 50022 standard (35mm × 7.5mm), and is installed on a flat surface inside the cabinet, away from heat sources such as frequency converters and contactors.

Buckle installation: Insert the upper hook of the controller into the upper edge of the guide rail, press the lower part of the controller until the lower buckle "clicks" to lock onto the lower edge of the guide rail (if unable to lock, check if the guide rail is bent, adjust and retry).

Disassembly method: Press the release button on the upper part of the controller, while pulling the lower part forward to disengage the buckle from the guide rail, and remove the controller (disconnect the power and wiring before disassembly).

2. Wiring specifications and safety requirements

(1) Preparation before wiring

Power off confirmation: Before wiring, all relevant power sources must be disconnected, and a multimeter must be used to confirm that there is no voltage to avoid electric shock.

Wire selection:

Power wire: 12-18 AWG copper wire, current carrying capacity ≥ controller maximum current (LF/LV ≤ 0.5A, LS ≤ 0.1A).

Sensor wires: Thermocouples use the same type of compensating wire (such as JX-HS-FF for J-type), RTDs use 3-core shielded wire (20-24 AWG), and the shielding layer is only grounded at the sensor end.

Output wire: Depending on the load current, an additional RC suppressor (Watlow P/N 08040147-0000) needs to be connected in series for inductive loads.

(2) Core wiring example (LF/LV single circuit protection)

Power wiring: L1 (live wire) is connected to terminal 1, L2 (neutral wire) is connected to terminal 2, and a 2A slow melting fuse (250V) is connected in series. The live wire end needs to be connected to a circuit breaker (for easy power-off maintenance).

Sensor wiring (J-type thermocouple): The positive (non red) terminal of the thermocouple is connected to terminal 5, and the negative (red) terminal is connected to terminal 10. The extension wire needs to be a J-type compensating wire to avoid copper wires.

Output wiring: Relay COM terminal is connected to terminal 6, NO terminal is connected to one end of the contactor coil, and the other end of the coil is connected to L2; NC terminal is backup (can be connected to an alarm light), inductive load (contactor coil) is connected in parallel with an RC suppressor (between terminal 6 and NO terminal).

External reset wiring: One end of the external button is connected to terminal 9, and the other end is connected to terminal 6 (COM end). The button is of the instantaneous and constant on type (such as Schneider XB2-BA31).

(3) LS series dual sensor wiring

Power wiring: Connect L1 to terminal 1, L2 to terminal 2, and connect 2A slow melting fuses in series.

Dual sensor wiring (K-type thermocouple): Sensor 1 is connected to positive terminal 5 and negative terminal 10; The positive terminal of sensor 2 is connected to terminal 4, and the negative terminal is connected to terminal 9. The installation positions of the two sensors should be close (temperature difference ≤ 20 ° C).

Output wiring: The relay COM terminal is connected to terminal 6, and the NO terminal is connected to the heating tube power circuit. After triggering the protection, the NO terminal is disconnected, cutting off the heating tube power supply.

(4) Safety wiring requirements

Electrical isolation: Sensor cables, power cables, and output cables need to be wired separately (with a spacing of ≥ 10cm) to avoid electromagnetic interference; The grounding terminal of the controller (if any) needs to be connected to a protective ground (grounding resistance ≤ 4 Ω).

Installation in hazardous areas: Explosion proof junction boxes and armored cables are required for Class 1 Div. 2 hazardous areas, with terminal tightening torque ≥ 0.56 Nm, and live plug and unplug wiring is prohibited.

Anti misoperation wiring: strictly follow the terminal label for wiring, and do not reverse the positive and negative terminals of the power supply or the sensor (otherwise abnormal display or failure to trigger protection).

3. Analysis of Typical System Wiring Diagram (Industrial Oven Protection)

System composition: The main controller (Watlow Series CV) controls the temperature of the oven, while the LF series serves as redundant protection to prevent overheating caused by main controller failure.

Wiring logic:

The LF sensor and the main controller sensor are installed at different positions in the oven to avoid single point failures.

The LF output is connected in series with the main contactor coil circuit, and the main controller output is also connected in series with this circuit, forming a "double safety".

After triggering the LF protection, the contactor coil loses power, cutting off the power supply to the heating tube, and the ALARM light is on, requiring manual reset (or external button reset).

Troubleshooting and Maintenance

1. Common faults and solutions

Possible causes of malfunction, troubleshooting steps, and solutions

No display/action, ALARM light not on. 1. Power not connected or circuit breaker tripped