How to Read a Wiring Diagram For a Mechanically Held Lighting Contactor

Understanding the complexities of electric wiring diagrams can be daunting for even a highly experienced electrician. Knowing how to read a schematic and find specifics in the wiring diagrams for a mechanically held lighting contactor is key to being able to troubleshoot, maintain, and upgrade any system with this type of contactor. This article will explain exactly how to read and interpret a diagram for a mechanically held lighting contactor, and what components from your system need to be inspected to keep it running optimally.

Electrical wiring diagrams are drawings that provide precise legend and orientation points for all the connections in an electrical system. The symbols used for the different types of contactors, such as manually operated and mechanically held lighting contactors, and what each element looks like is a key skill in being able to troubleshoot and maintain this equipment. This can be especially confusing when dealing with a mechanically held lighting contactor.

Safety First

Before beginning to work on any wiring diagram, it is important to make sure that all safety precautions are taken. Turn off all power connected to the device. Not only is this important for personal safety, but it can also prevent damage to other components if the proper circuit connections are made.

Once the contractor is turned off, the cover may need to be opened to expose the contactor itself. Carefully inspect the circuit board and component connections inside to ensure everything looks correct. Pay attention to any wires that may be disconnected.

Components of the Mechanical Contactors and Their Designation on Schematic Diagrams

The most fundamental component of a mechanically held lighting contactor are the two contact points that make up the contacts, designed to carry electric current. Additionally, a mechanical link (also called a "trip arm") is used to cut off the current. Depending on the complexity of the wiring system, other electrical elements may be included in the schematic, such as overload protectors, time-delay relays, coils, and pilot lights.

When viewing the wiring diagram for a mechanically held lighting contactor, pay particular attention to the specific designations for those components. The contacts are typically labeled as "A" and "B", while the link is labeled "T". Additionally, the overload protection, time-delay relays, coils, pilot lights, and other electrical elements will have their own markings as well.

In some cases, the wiring diagram might not show all the components, so it is important to look carefully at the entire system to ensure nothing vital is missed. It is also important to be aware of the difference between single-phase and three-phase systems, since this affects the way the wiring diagram is presented.

Reading the Wiring Diagram

Once all components have been identified, it is possible to begin reading the wiring diagram. There will usually be two diagrams – one showing a manual operation and the other showing automatic operation. On the manual side, there will be a set of arrows representing the current flow through the contacts, while the automatic side will show either a dotted line or arrow nearest the trip arm. This indicates that power is constantly supplied to contact A no matter the position of the trip arm, unless manually powered off.

There will also be arrows connecting certain components together, to show their relationship in the system. These arrows indicate the direction of loading, meaning which wires become active when a certain component is switched on or off. Pay special attention to the connections between the overload protector and the pilot light, as well as between the time delay relay and the coil.

Common Troubleshooting Errors

When troubleshooting any equipment with a mechanically held lighting contactor, keep in mind the most common errors associated with the wiring and system components. Pay close attention to overloaded contacts, loose connections, and defective shunts — these are the most likely cause of malfunctions in mechanically held contactor systems. Additionally, it is important to test that the trip arm works properly, either manually or automatically.

Finally, if the problem is found within the wiring diagram, ensure that all the wire numbers, labels, and designations match correctly if rewiring any part of the system. Faulty wiring can not only prevent the system from working properly, but also interfere with proper identification of the component parts, creating further trouble for diagnosing faults.

Conclusion

Understanding and reading a wiring diagram for a mechanically held lighting contactor can be a difficult task, particularly for the inexperienced technician. By carefully inspecting each component before beginning to work on the schematic, paying attention to all component parts, and double-checking for accuracy during diagnosis, you can prevent costly mistakes. This article provides an overview of how to read and interpret a wiring diagram for a mechanically held lighting contactor and the potential problems that can occur.

Cr460 Series Lighting Contactors

Contactorotor Starters

Volume 10 Tab 4

Lighting Contactors Information

Class 8903 Type Lx Mechanically Held Lighting Contactor 2 Thru 12 Pole Forms G10 3 Wire Power Photocell R6 Two Control Relay C Hoa Selector Switch Latch Coil Ch1 14 On