How to install a portable generator transfer switch

What is a transfer switch?

A transfer switch allows you to transfer power from a primary source, such as the utility grid, to a secondary source, like a portable generator. It ensures safe and efficient power delivery to your home and prevents dangerous bidirectional reverse power feeding by ensuring that two power sources are never connected simultaneously.

A transfer switch often has multiple circuits, allowing you to assign power to specific loads, such as heaters, refrigerators, or lights. You can run multiple devices simultaneously, and switching between circuits is simple and safe. For more details, please see “How a generator transfer switch works“.

Why install a transfer switch?

• Safety: Prevents back-feeding, which can be dangerous or even fatal for utility workers and can damage your home’s electrical system and appliances.
• Convenience: Allows you to power your home circuits directly through your breaker panel instead of relying on extension cords.
• Ease of use: Simplifies switching between the utility grid and generator power.

Types of transfer switches

• Manual transfer switch: Requires manual switching of the power source. It is less expensive and easier to install.
• Automatic transfer switch: Automatically switches power from the utility to the generator during an outage. It is more expensive and requires professional installation.

Planning and preparation for installing a manual transfer switch

1. Choosing the right transfer switch

For home backup power, a manual transfer switch (mts) is recommended. Manual switches are reliable, simple to operate, and prevent back-feeding into utility lines.

Key considerations:

• Amperage rating: Match the switch to your generator’s output (e.G., 30a generator → 30a switch; 50a generator → 50a switch). Proper matching prevents overloads and ensures safe operation.
• Number of circuits: Decide how many essential circuits you want to back up. Manual transfer switches typically support 6–12 circuits.
• Safety certification: Choose a UL-listed switch.

2. Determining critical circuits

Not all home circuits require generator power. Focus on essential circuits that maintain safety and functionality during outages:

• Furnace or heating system
• Refrigerator and freezer
• Well pump or water system
• Key lighting areas
• Medical equipment
• Sump pump or other safety-critical devices

3. Essential components and tools

Components:

• Manual transfer switch kit
• Generator inlet box
• Appropriately sized wire (e.G., 10 awg for 30a, 6 awg for 50a)
• Electrical conduit and fittings
• Wiring connectors (wire nuts, lugs, grounding hardware)
• Breaker handles or replacement breakers if required

Tools:

• Screwdriver set
• Wire strippers and cutters
• Drill with appropriate bits
• Voltage tester or multimeter
• Level for precise mounting
• Fish tape or wire puller
• Electrical tape and cable ties

4. Selecting installation sites

Transfer switch location:

Mount the manual transfer switch next to your main service panel for easy wiring.

Ensure there is enough clearance around the panel for maintenance, future inspections, and safe operation.

Install on a firm, dry surface, protected from direct sunlight.

Generator inlet box location:

Place the inlet box outside near the generator’s location.

Position it at a height and location that complies with electrical codes.

Minimize long cable runs and provide weather-protected connections.