How to Install an Obsolete Knife Switch Electrical Panel

Knife switches were commonly used in electrical panels from the late 19th century up until about the 1950s. While considered obsolete today, some homes and buildings still rely on antique knife switch panels. Replacing or upgrading these outdated systems can be dangerous and is best left to licensed electricians. However, for those determined to install an antique knife switch panel themselves, here is a comprehensive guide on how to do so safely.

Understanding Knife Switch Panels

Knife switches operate by manually opening or closing a circuit using a swinging blade mechanism. They allow power to be routed to different parts of a home or building.

Here are some key facts about antique knife switch electrical panels:

• Made of ceramic, slate, or wood - Early knife switch panels were made of materials like ceramic, slate, and wood which are combustible and provide less protection compared to modern metal enclosures.

• No circuit breakers - Knife switches operate manually and lack automatic circuit breakers that modern panels have for overload and short circuit protection. This makes them more prone to electrical fires.

• Substantial arc flashing - The swinging knife blade action can generate significant arc flashes when opening or closing the circuit. This can lead to very dangerous electrical shock and burn hazards.

• No grounding - Older knife switch systems often lack proper grounding which provides a safe path for current in the event of a fault. Ungrounded panels increase the risks of electrocution.

Dangers of DIY Knife Switch Installation

Installing a vintage knife switch panel comes with considerable dangers that should prompt calling a professional electrician. Hazards include:

• Electrocution - From exposed high voltage connections and outdated or improper wiring. Can cause serious injury or death through electrical shocks and burns.

• Arc flashes - Intense arc flashes can severely burn skin and eyes or cause blindness. Should be treated as seriously as looking directly at the sun.

• Fire - Overloaded, shorted, or loosely connected wires can overheat and ignite combustible panel materials leading to electrical fires. Fires fuelled by electricity spread incredibly quickly.

• Property damage - Faulty antique electrical work can damage or destroy buildings and possessions.

In summary, the risks inherently involved in installing and operating a knife switch panel make professional installation strongly advised for safety.

Gathering the Required Tools and Materials

If you still plan to install an antique knife switch panel yourself, you will need to gather these essential supplies:

Tools

• Clamp meter - To measure load currents for properly sizing switches and wiring
• Screwdrivers - For mounting hardware and wire connections
• Pliers - For bending and cutting wires
• Drill & bits - For drilling mounting holes
• Cable stripper - For removing wire insulation
• Ladder - For accessing the installation location
• Safety glasses & gloves - Critical PPE for eye and hand protection

Materials

• Knife switches - Industrial surplus or vintage switches sized for your electrical loads
• Fuses - Time delay fuses for each switch, matched to load current
• Bus bars - Copper bars for current transfer between switches
• Insulators - Ceramic mounts to isolate energized parts
• Enclosure - A vintage wood or slate panel or modern metal cabinet
• Wiring - Sufficient gauge and insulation for currents
• Conduit - To protect wiring between devices
• Mounting hardware - Screws, bolts, clamps, etc to mount equipment

Ensuring you have high quality materials designed for electrical use is vital for safety.

Step-by-Step Installation Guide

With the proper tools and materials gathered, you can now proceed carefully with the installation:

1. Mapping the Electrical Loads and Layout

• Use the clamp meter to measure the current draw from each existing circuit that will be connected to the new panel.

• Draw up a schematic diagram mapping all the electrical loads and their required current ratings.

• Decide on the physical layout for where components will be positioned in the panel enclosure. Strive for neat, orderly wiring.

2. Mounting the Enclosures and Bus Bars

• Bolt or screw the vintage panel enclosure or modern cabinet securely to the wall with included hardware.

• Mount insulated bus bars horizontally in the enclosure to transfer current between knife switches. Space evenly to allow wires to be neatly routed.

3. Installing the Knife Switches and Wiring

• Match switches to electrical load currents and mount tightly to the enclosure surface with included hardware.

• Run suitably gauged copper wiring between each switch, fuse, bus bar, and load connection point.

• Keep live conductors separated and insulated. Route wires neatly through conduit.

• Label wires clearly at both ends so you can match their destinations when making connections.

4. Connecting the Wiring to Components

• Follow all diagrams carefully when making wire connections.

• Strip insulation properly and secure wires tightly to terminals with screws or clamps.

• Ensure connections are mechanically and electrically sound. Failure points here can lead to arcing faults or loose resistance heating.

5. Testing Operation and Safety

Before energizing the panel:

• Verify all connections are tight with good contact.

• Ensure no bare conductors are exposed.

• Check fuses are properly rated for the loads.

• Keep hands clear of switch contacts when testing! The arc flash can seriously burn you.

Initially energize the panel without any loads connected and check for issues. Then begin testing each circuit one by one under safe no load conditions. If all checks out, connect loads and test for proper operation.

Important Safety Precautions

When dealing with a live antique electrical panel, extreme caution should be exercised:

• De-energize the panel - Lock out all power sources before working on the panel.

• Protect against arcs - Wear certified arc flash PPE like jackets, hoods, and gloves.

• Mind enclosure condition - Replace combustible panels made of wood or slate.

• Address ground faults - Installing proper grounding should be top priority for safety.

• Know your limits - If beyond DIY abilities, hire a licensed electrician to avoid dangers.

Regular inspection and maintenance should be performed to catch any emerging issues over time.

While obsolete, knife switch panels hold unique antique appeal. But the myriad safety concerns mean only qualified electricians should undertake installation and repairs. I hope this guide has provided insights into upgrading these antiquated electrical systems for those determined to do so themselves, but strongly advise properly delegating this hazardous work to professionals. Please stay safe!