The call comes at 2:14 AM. A conveyor motor at the packaging line is running backward, sending product boxes crashing into each other. The maintenance tech swears he followed the wiring diagram when he replaced the cam switch yesterday afternoon. But somewhere between the schematic and the terminal strip, two phases got crossed—and now the night shift is hand-sorting boxes while the day crew calculates downtime costs.
Wiring a cam switch correctly the first time isn’t complicated, but it requires understanding terminal conventions, following the right diagram for your application, and verifying every connection before you close the panel door. This guide walks you through the complete process—from safety lockout to final testing—with wiring diagrams for the most common industrial applications: simple ON/OFF isolation, 3-position selectors, three-phase motor reversing, power changeover, and measurement switching.
Whether you’re an apprentice electrician installing your first control panel or an experienced technician replacing a failed switch in an existing system, this step-by-step reference will help you get the wiring right.
Safety First: Pre-Wiring Checklist
Before you strip a single wire, complete these safety steps:
De-energize and Lock Out the Circuit: Turn off the circuit breaker, apply lockout/tagout, and verify with a voltage tester on all phases and neutral. Never trust switch position alone.
Verify Ratings Match Your Load: Check the nameplate for rated current (Ie), voltage (Ue), and utilization category (AC-21 for resistive, AC-23 for motors). For motors, choose 1.5× the full-load current to handle starting inrush.
Gather Tools: Wire strippers, insulated ferrules, crimping tool, torque screwdriver, multimeter, cable ties, and labels. IEC installations require ferrules on stranded wire.
Identify Wire Colors: IEC: Brown (L1), Black (L2), Gray (L3), Blue (N), Green-Yellow (PE). NEC: Black (L1), Red (L2), Blue (L3), White (N), Green (Ground).
Verify Grounding: Bond the switch enclosure to protective earth. Confirm continuity to panel ground.
Understanding Cam Switch Terminals
Cam switch terminals aren’t standardized across manufacturers, which is why miswiring happens. Learning how to read the nameplate and identify terminal functions prevents the most common installation errors.
Common Terminals (Input): The common terminal is where you connect the incoming power or signal. On a 3-position selector switch (1-0-2), the common terminal is often labeled “0” or “C.” On motor reversing switches, you’ll see three common terminals—one for each phase—labeled L1, L2, L3 or U, V, W. Power flows into these terminals.
Output Terminals (Switched Circuits): Output terminals connect to the loads being controlled. On a 3-position selector, outputs are typically labeled “1” and “2” (or “A” and “B”). When the handle is in Position 1, the common connects to Output 1. When the handle is in Position 2, the common connects to Output 2. In the center OFF position, the common is disconnected from both outputs.
Βοηθητικές επαφές: Some cam switches include auxiliary contacts—small additional contacts rated for signaling circuits (typically 3A-6A). These are used to send status signals to PLCs, indicator lights, or interlocking circuits. Auxiliary terminals are usually labeled separately with numbers like 13-14 (NO contact) or 21-22 (NC contact), following IEC 60947-5-1 conventions.
Reading the Program Code: Many industrial cam switches use a program code or switching table printed on the side or in the datasheet. This code defines which contacts close in each handle position. For example, a program code “0-1-2” means Position 0 opens all contacts, Position 1 closes one set, Position 2 closes a different set. Always cross-reference the program code with your wiring diagram before starting.
Quick Reference: Terminal Numbering by Brand
| Κατασκευαστής | Common Terminal(s) | Output Terminals | Σημειώσεις |
| Generic/IEC | 0, C, or L1/L2/L3 | 1, 2, 3, 4 (or A, B, C) | Position numbers often match output terminals |
| ABB | L1, L2, L3 (input) | T1, T2, T3 (output) | Follow IEC conventions; consult terminal diagram |
| Schneider | 1, 3, 5 (input) | 2, 4, 6 (output) | Odd numbers = input, Even = output |
| VIOX LW26 | L1, L2, L3 (input) | 1, 2, 3 or T1, T2, T3 (output) | Terminal diagram on switch body; program code on label |
Always consult the manufacturer’s wiring diagram. When in doubt, use a continuity tester: with the switch de-energized, rotate the handle through each position and test which terminals show continuity. Map the switching program manually if the documentation is unclear.
Wiring Diagrams by Application
Here are the five most common cam switch wiring scenarios you’ll encounter in industrial and commercial installations. Each includes terminal connections and typical applications.
1. Simple ON/OFF Switch (Isolation/Load Control)
The simplest configuration: a 2-position cam switch that opens and closes one or more circuits simultaneously. All poles operate together—when the handle is in Position 1 (ON), all contacts close; when in Position 0 (OFF), all contacts open.
Terminal Connections:
- Connect incoming power (L1, L2, L3) to the common terminals
- Connect outgoing wires to loads (motor, heater, lighting panel) to output terminals
- For single-phase: Line to common, Load to output. Neutral connects directly (not through switch)
- For three-phase: L1/L2/L3 to commons, Motor U/V/W to outputs
Εφαρμογές: Manual disconnect switches for equipment isolation during maintenance, emergency stop switches, backup isolation when primary disconnect fails, simple load ON/OFF control.
Βασικό σημείο: This is a switching device, not a protective device. It doesn’t provide overcurrent or short-circuit protection—you still need a circuit breaker or fuses upstream.
2. 3-Position Selector Switch (1-0-2 Changeover)
A versatile configuration where the common terminal connects to one of two outputs, or disconnects from both. Positions: 1 (Output 1), 0 (OFF), 2 (Output 2).
- Power source → Common terminal (labeled “0” or “C”)
- Load A → Output 1 (labeled “1”)
- Load B → Output 2 (labeled “2”)
Εφαρμογές: Mode selection (AUTO/OFF/MANUAL), dual-speed fans, pump alternation, lighting scenes.
3. Three-Phase Motor Reversing (Forward-Off-Reverse)
The most requested wiring diagram. A 3-pole cam switch swaps two motor phases to reverse rotation.
Terminal Connections:
Supply (commons): L1 (Brown)→Common 1, L2 (Black)→Common 2, L3 (Gray)→Common 3
- FORWARD: U→L1, V→L2, W→L3
- OFF: All open
- REVERSE: U→L3, V→L2, W→L1
Swapping L1 and L3 reverses the motor. L2 stays on V.
Εφαρμογές: Conveyors, hoists, cranes, reversible fans.
Κρίσιμη Προειδοποίηση: Never reverse while running. Always stop at center OFF first.
4. Three-Phase Power Changeover (Mains/Generator Transfer)
A manual transfer switch for selecting between two power sources without backfeed risk.
Terminal Connections:
- Source A (Mains): L1A, L2A, L3A → Commons 1A, 2A, 3A
- Source B (Generator): L1B, L2B, L3B → Commons 1B, 2B, 3B
- Load: T1, T2, T3 → Outputs
Positions: 1 (Mains), 0 (both isolated), 2 (Generator).
Εφαρμογές: Backup power, dual utility feeds, maintenance switching.
5. Voltmeter/Ammeter 3-Phase Selector
A 4-position cam switch connects one meter to each phase sequentially.
Terminal Connections:
- Phase inputs: L1, L2, L3 → Commons
- Meter input → Output terminal
Positions: 0 (OFF), 1 (L1-N), 2 (L2-N), 3 (L3-N).
Εφαρμογές: Motor control panels, distribution panels, generator monitoring.
Rating Note: Voltmeter switching needs minimal current rating; ammeter switching must match the full load current.
Διαδικασία εγκατάστασης βήμα προς βήμα
Follow this sequence to wire and commission a cam switch correctly.
1. De-Energize and Lockout Circuit: Turn off the upstream circuit breaker. Apply your personal lockout device and warning tag. Test for voltage on all conductors before touching anything.
2. Mount the Cam Switch: Verify the panel cutout matches the switch mounting dimensions (typically 22mm, 30mm, or 40mm diameter for rotary cam switches). Install the gasket if supplied. Insert the switch from the front, secure with the mounting nut from the rear. Tighten firmly but don’t overtighten—you’ll crack the housing.
3. Prepare Wires: Strip wire ends to the length specified by the switch manufacturer (typically 8-10mm). Install insulated ferrules on all stranded wires—crimp firmly with a proper ferrule tool. Ferrules prevent strand breakage and ensure reliable contact.
4. Connect Wires to Terminals: Follow your wiring diagram precisely. Connect incoming power to common terminals, outgoing wires to output terminals. Insert wires fully into the terminal, tighten terminal screws using the specified torque: typically 1.2-1.5 Nm for M3.5 screws, 2.0-2.5 Nm for M4 screws. Under-torqued terminals heat up and fail; over-torqued screws strip threads.
5. Route and Secure Wiring: Route wires neatly away from sharp edges and moving parts. Use cable ties to dress wiring into bundles. Maintain separation between power wiring and control signal wiring to prevent electrical noise.
6. Label Everything: Use permanent labels to mark each terminal with its circuit designation. Label the switch handle positions (FORWARD/OFF/REVERSE, or 1/0/2, etc.). Future technicians will thank you.
7. Verify with Continuity Test: Before restoring power, use a multimeter in continuity mode. Rotate the handle through each position and verify that the correct terminals show continuity in each position. This catches wiring errors before you energize the circuit.
8. Close Enclosure and Restore Power: Replace the panel door or cover. Remove your lockout device. Restore power at the circuit breaker.
9. Test Operation: First, test under no-load (motor disconnected or breaker off downstream). Verify the switch operates smoothly through all positions. Then test under load. For motor applications, verify rotation direction in each position before running at full speed.
Troubleshooting Common Wiring Issues
Motor Runs in Wrong Direction
- Αιτία: Two phases are crossed.
- Διόρθωση: De-energize. Swap any two of the three motor phase wires (U and W, for example). Re-test.
Intermittent Contact or Arcing
- Αιτία: Loose terminal connections, worn or oxidized contacts, or inductive load without suppression.
- Διόρθωση: Retorque all terminal screws to spec. Inspect contacts for pitting or burning; replace contact kit if damaged. For inductive loads (motors, solenoids), add an RC snubber (0.1µF capacitor and 100Ω resistor in series) across the switched contacts to absorb back-EMF.
Breaker Trips When Switch is Operated
- Αιτία: Short circuit from crossed wires, damaged insulation, or insufficient clearance between phases.
- Διόρθωση: De-energize. Inspect all wire insulation for damage. Verify phase-to-phase and phase-to-ground isolation with a megohmmeter (insulation resistance should be >1MΩ). Check that wires aren’t pinched under the mounting hardware.
Switch Doesn’t Behave as Expected (wrong circuits switching)
- Αιτία: Wrong cam program code selected, or terminals misidentified during wiring.
- Διόρθωση: Verify the switch program code matches your application. Consult the manufacturer datasheet for the switching table. If necessary, map the actual switching behavior with a continuity tester and re-wire to match.
Conclusion & Best Practices
Wiring a cam switch correctly comes down to three things: understanding which terminal does what, following the right diagram for your application, and verifying every connection before you close the panel. The extra five minutes testing continuity in each position prevents the 2 AM callback when something goes wrong.
Best practices: always use ferrules on stranded wire, apply the correct terminal torque, label every connection. Document your work with photos or a marked-up wiring diagram for the maintenance file. For motor reversing applications, never switch direction while the motor is running—always pass through the OFF position.
Need help selecting the right cam switch for a custom application, or have questions about wiring configurations? Contact VIOX Electric’s application engineering team. We provide technical support, custom cam programming, and fast delivery for control panel builders and OEM manufacturers worldwide.
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