OTEC 225A transfer switch

A transfer switch is what makes a standby generator legal and safe. It isolates your house from the utility before the generator energises anything, so the generator can never back-feed the line a utility crew is working on. It is not optional and it is not a place to economise.

The switch is sized to your electrical service, not to the generator. A 200A service takes a 200A switch whether the generator behind it is 13kW or 20kW. That is why we confirm your service size at the site survey before specifying one — ordering to the generator instead of the service is the most common and most expensive mistake on these jobs.

Service-entrance rated versions include the main disconnect, so the switch can replace your existing main rather than sit beside it. That often simplifies the install and reduces what has to be reworked at the panel — but whether it is allowed depends on your meter configuration and your city.