Automatic transfer switches

How it works

The switch is wired between your utility service and your house circuits. It watches the voltage coming in from Con Edison. When that voltage drops out, it starts the generator, waits for steady output and then connects the house to the generator. When the utility comes back and stays stable, it switches back and lets the generator run briefly to cool down before stopping.

Why it is a safety device

A transfer switch keeps the generator and the utility completely separate. Without it, a generator connected to house wiring can send power back out onto the lines, where it can electrocute a line worker who thinks the line is dead. That is called backfeeding. It is dangerous and illegal, and it is never acceptable to connect a generator to house wiring without a proper switch or interlock.

Choosing a switch

The type of switch depends on how much of the house you want covered.

• Whole-house, service-rated: sized for the full service, often 200 amps, and installed at the service entrance
• Partial or essential-circuit: feeds a smaller panel of chosen circuits
• With load management: lets a mid-size generator cover a large house by holding back heavy loads until there is room

Installation

This is licensed electrical work at the main service, with a permit and inspection. The utility may have to pull the meter. In Harrison, the contractor files with the Town and Village. Planning the switch together with any panel upgrade or EV charger avoids doing the same work twice. See electrical panel upgrades.

Replacing an existing switch

If your generator is fine but the switch has failed, is too small after a panel upgrade, or is manual, it can often be replaced on its own. The electrician confirms the new switch works with your generator's controller before ordering.

Questions worth asking

Ask the electrician what amp rating they recommend and why, whether the switch is service-rated, and whether load management is included. Ask how the switch will be tested at start-up and during each service visit, and whether it can send alerts with the generator controller. If you also plan an EV charger or heat pump, mention it now, since it may change the switch size or the way loads are managed during an outage.

Questions homeowners ask