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How to Install a Manual Transfer Switch for a Portable Generator

Ask This Old House master electrician Scott Caron visits Alaska to install a portable generator with a manual transfer switch to power hardwired appliances like a well pump and heating system using unleaded gasoline


  1. Mount the manual transfer switch near the main electric panel.
  2. Select up to 10 circuits to be powered by the generator (240 volt circuits require two spots on the transfer switch).
  3. Turn off power to the house at the main electric shut off.
  4. Remove the cover on the main electric panel (work inside the electric panel is only recommended for licensed electricians).
  5. Locate an available knockout hole on the electric panel and remove the plug. Attach the armored cable from the transfer switch to the electric panel.
  6. Connect the ground and neutral wires from the transfer switch to the appropriate bus bars on the main panel.
  7. Locate the first circuit to be powered by the generator and remove the power wire on the existing circuit breaker. Replace that wire with the red wire from the transfer switch marked “A.” Splice the black wire marked “A” from the transfer switch to the removed power wire using a wire nut. Repeat this process for all 10 circuits, ensuring the red and black wires from the transfer switch are a matched pair.
  8. Use 10-3 non-metallic wiring to connect the transfer switch to a power inlet outside.
  9. Use the provided generator cord to connect the power inlet to the generator (or make your own cable if a longer one is desired using bulk wire and connectors).
  10. Ensure the generator has unleaded fuel and oil inside, then start the generator.
  11. To test the wiring connections, flip the switches on the transfer switch from “Line” to “Gen.” The generator should power the selected circuits.