How to Replace Obsolete Knife Switches in your Facility's Electrical System

Introduction

Replacing obsolete knife switches in an electrical system can seem like a daunting task, but with proper planning and safety precautions, it can be done efficiently. As the facility manager, it is your responsibility to ensure your building's electrical systems are up-to-date and functioning properly. In this article, I will walk you through the complete process of replacing those old knife switches with new ones.

Reasons to Replace Knife Switches

There are several good reasons to swap out outdated knife switches:

• Safety - Old switches can become loose or corroded over time, increasing the risk of dangerous arcing or even fire. New switches are designed with safety features not found in obsolete models.

• Reliability - New knife switches are less prone to failure compared to older models. Replacing them now prevents potential downtime and disruption later on.

• Capacity - Upgrading to higher amperage knife switches allows you to expand circuits in the future. New switches can accommodate larger loads.

• Maintenance - Modern switches are easier to inspect, service, and replace individual components. Older switches may require total replacement when they fail.

• Code compliance - In some cases, keeping outdated switches violates electrical codes or local regulations. Replacing them brings your facility up to current standards.

Choosing New Knife Switches

When selecting new knife switches, consider the following factors:

• Electrical load - Choose switches rated for the amperage and voltage of the circuits they will control. Allow room for future capacity increases.

• Physical size - Pick switches that fit the existing mounting footprints. Measure space limitations carefully.

• Enclosure type - Indoor, outdoor, dustproof, and watertight enclosures are available. Select enclosures suited for your environment.

• Electrical standards - Verify switches are tested and listed by UL or other agencies to meet local electrical codes.

• Features - Choose options like visible blades, auxiliary contacts, and arc chutes for added safety and functionality.

• Cost - Get quotes from multiple switch manufacturers to find the best value. Focus on quality and compliance over lowest price.

Workflow for Replacing Knife Switches

Once you have the new switches, follow this general workflow for replacing the old units:

1. Disconnect and lock out power

Shut down the feeder breaker or switch supplying power to the knife switch you are replacing. Lock it in the OFF position using a padlock and lockout tag. Check for dangerous voltage before proceeding.

2. Remove old switch

Take photos of the wiring connections. Disconnect the conductors from the switch terminals and remove any mounting hardware. Carefully extract the old switch without damaging wires.

3. Install new switch

Secure the new knife switch using the mounting holes and hardware. Make wiring connections referencing your photos. Double check connections are tight and insulated properly.

4. Verify operation

Restore power to the switch. Use a voltmeter to check for voltage on both load and line sides. Operate the switch several times to confirm smooth operation.

5. Update documentation

Add the new switch specs to your electrical drawings, maintenance records, and asset inventory. Include photos of the installed switch and surrounding wiring.

Safety Tips

• Use personal protective equipment like insulated gloves and mats when working on live components.

• Keep flammable materials away from the workspace in case of arcing or sparks.

• Never close or open a knife switch under load. Always disconnect the power first.

• Replace switches one at a time to avoid extended downtime.

• Have fire extinguishers ready in case of any electrical mishaps.

Conclusion

While replacing obsolete knife switches requires careful planning and safety measures, the long-term benefits are substantial. Upgraded switches provide better protection, performance, and compliance. By methodically swapping out old switches over time, you can modernize your facility's entire electrical system. Just be sure to follow codes and industry best practices throughout the replacement process. With the right knowledge and preparation, you can execute this critical electrical upgrade project smoothly and successfully.