Selection and Installation Guide to Control Relays

Control relays provide invaluable signal switching and amplification in industrial control panels. Selecting the right relay models for an application and properly installing them determines reliability. Consider these key factors and best practices.

• Choose relay electrical ratings to suit loads
• Ensure adequate clearance for heat dissipation
• Use socket mounts for easy replacement
• Employ interface modules for sensor compatibility

Control relays may seem simple, but choosing incorrectly can lead to premature failure. Whereas overlooking proper installation procedures can produce loose connections and noise-prone circuits. With critical processes at stake, carefully select and mount relays.

Control Relays – Factors to Consider

Here are a few things to keep in mind while investing your money in control relays:

1. Electrical Load Considerations

Consider voltage, current draw, and switching capacity of loads the relays will control. Standard control relays operate from 5 to 240V AC/DC and switch up to 15 amp residential loads or 6 amp inductive. For heavier industrial loads, contactors can handle up to 600V and 200A.

Use narrow voltage bands for AC relays to prevent hum and chatter. Check motor start surge currents fall within relay specs if directly switching inductive loads. And allow a safety margin below published contact ratings – 20-30% for resistive loads, 50% for motors.

2. Mechanical Design Factors

Consider the mechanical life expectancy of relays in continuous switching applications like conveyor belts or pumps. Standard life expectancies range from 100,000-500,000 cycles. But more durable 10-20 million cycle relay contacts suit highly repetitive automation tasks.

Also, ensure good coil suppression to prevent back EMF spikes from inductive loads damaging switch contacts. Look for varistor, capacitor, or zener diode suppression across coils for reliable performance.

3. Thermal Environment

Determine the ambient operating temperatures relays will experience and verify rated coil insulation classes. Though industrial control panels see fairly stable temps, areas like steel mills and HVAC plants span a wide range. High density panel designs also require vigilant heat dissipation planning with adequate relay spacing.

4. Interface Modules

Many relays feature standard “ice cube” pin layouts, but others utilize unique wiring interfaces. For sensor compatibility, snap-on socket adapter modules convert disparate connections to uniform plugs, allowing interchangeable relay models. These modules also simplify replacement.

Proper Installation

Always use manufacturer-specified torques for mounting hardware – usually 7-10 in-lbs for socket mounts to avoid loosening. Align pins properly and fully seat relays. Ensure adequate ventilation by spacing at least 1” apart and 3” from enclosure walls while avoiding placing above heat-producing components.

Connect wires securely with minimal untwisting and strain relief. Stranded conductors often benefit from ferrules to avoid fraying inside screw terminals. Double-check all wiring before energizing.

Conclusion

Applying control relays requires carefully weighing electrical and mechanical needs against environmental constraints. And proper installation practices ensure flawless performance for years of service. 

Discuss your next relay-based project with TOSUNlux to leverage decades of design experience tailored to your application.