How to Wire a Transfer Switch to a Circuit Breaker Panel

Having a generator to provide power to your home can be a benefit if you live in an area that is prone to extended power outages due to storms or other issues.

Transfer switches protect linemen from being electrocuted.Transfer switches protect linemen from being electrocuted.
The generator can provide you with enough electricity to power necessary appliances such as a refrigerator or water heater. When installing an emergency generator, you must also install a transfer switch. This is a safety feature that prevents electricity created by your generator from being carried out to your utility's power lines, where it can kill or injure workers.

List your circuits in their order of importance and label them with letters. For instance, your water heater is line "A" and your refrigerator is line "B."

Install the transfer switch and sub-panel 18 inches to the side of your main electrical box. The transfer switch and sub-panel can be a single unit or two separate units, depending on the manufacturer.

Switch off all of the circuit breakers inside your main electrical box.

Turn off the main breaker on the outside of the box. Do NOT touch any wires above this breaker as they are live and you will be killed.

Take the cover off of the electrical box.

Open one of the knockout holes on the bottom of the electrical box with a hammer and chisel.

Slide the wires from the conduit at the bottom of the sub-panel through the hole in the bottom of the main box and connect the conduit to the bottom of the main electrical box.

Check the breakers inside the main electrical box and the one of the front of the box again to make sure that they are still turned off. Coming into contact with these wires when they're live can kill you.

Locate the breaker in the main box that corresponds with circuit "A" in the sub-panel (the water heater in this example). Disconnect the wire that is connected to this breaker by loosening the screw and removing the wire.

Feed the red and black wires labeled "A" to the circuit breaker for the water heater. Cut the red wire to remove any excess length that is not needed, keeping it long enough to reach the circuit breaker. Remove about 5/8-inch of the insulation from the wire with a wire stripper. Loop the wire around the screw on the breaker and tighten the screw.

Cut the black wire to match the length of the red wire and strip off 5/8-inch of the insulation. Attach the wires with a plastic connector cap and slide them into the side of the main box.

Wire the rest of the circuits by repeating Steps 9 through 11.

Connect 240-volt circuits to the handle tie switches. These are the double-pole (two breakers connected together) switches that are labeled "GEN," "OFF" and "LINE." Connect them using the same method you used for the single-pole breakers.

Attach the white (neutral) wire to the neutral bar through an unused hole. The neutral bar is the bar with holes located inside the main electrical box.

Attach the green (grounding) wire to the grounding bar. If there is no grounding bar, attach it to the neutral bar.

Re-install the cover of the main electrical box.

Label the chart on the transfer box so you can identify the connections between the transfer box and the main box.

Turn on all of the breakers in the main box, and all of the switches in the transfer box in the "line" position.

Things You Will Need

  • Transfer switch
  • Sub-panel breaker box
  • Drill
  • Screwdriver
  • Hammer
  • Chisel
  • Wire cutter and stripper
  • Electrical connector caps
  • Pen


  • Purchase a sub-panel box that contains enough circuits to meet your needs during a blackout. If there are eight appliances that you must have during a blackout, buy an 8-circuit panel; if there are 10 circuits, purchase a 10-circuit panel.
  • After you have completed the installation, hire a certified electrician to inspect the transfer switch. Your local municipality or insurance company may require it.


  • Improper wiring of the circuits can cause damage to your appliances, start fires or injure or kill someone.

About the Author

Carson Barrett began writing professionally in 2009. He has been published on various websites. Barrett is currently attending Bucks County Community College, pursuing a Bachelor of Arts in sports management.