A generator without a transfer switch can only run what you plug into it. A generator with one can power the house wiring itself, safely, without anyone standing in the dark with a flashlight and a pile of extension cords.
If you are shopping for a generator transfer switch this winter, the choice comes down to three setups. Each one does the same basic job in a different way.
What a Generator Transfer Switch Does
Your house is wired to take power from one source at a time: the utility. A transfer switch moves the house over to the generator and disconnects it from the utility line first.
That second part is the point. Without it, generator power can flow backward onto the utility line. ESFI calls this backfeed and warns that it can injure or kill utility crews and neighbors. FPL gives the same warning and tells customers never to connect a generator to the breaker or fuse box.
The National Electrical Code covers this in NEC 702.5, which requires transfer equipment that prevents the utility and the generator from being connected at the same time.
Automatic Transfer Switch
An automatic switch watches the utility. When the power drops, it starts the generator and moves the house over within seconds. When the power returns, it moves back and shuts the generator down.
This is the setup that goes with a permanent standby unit. It works when you are at work, asleep or out of town. Our Generac standby generator installation includes wiring the automatic switch at your panel.
Manual Transfer Switch
A manual switch is a small panel beside your main panel. It holds the few circuits you want on backup power, such as the fridge, a few lights and a bedroom AC. When the power goes out, you start a portable generator, plug it into an inlet on the outside wall and flip the switch.
It costs less than a standby system and keeps the house wiring protected. The tradeoff is that you have to be home, and you have to run the generator outdoors.
Interlock Kit
An interlock is a mechanical plate that mounts on your main panel. It lets you turn on the generator breaker only after the main breaker is off, so the two can never be on together.
Interlock kits are made for specific panel brands and models, so the kit has to match your exact panel. Some older or full panels cannot take one. A quick look at the panel tells us which options fit, and our panel upgrade service covers the ones that do not.
Where to Put a Portable Generator
Whichever switch you choose, a portable generator runs outside. CPSC says to keep it at least 20 feet from the house, with the exhaust pointed away from doors, windows and vents. Not on a porch, not in the garage.
Add a battery-powered carbon monoxide alarm inside, too. Exhaust from a generator can reach lethal levels indoors even with a window open.
Permits and Inspections in St. Johns County
Connecting a generator to your home wiring is licensed electrical work, and it needs a permit. In Nocatee, Palm Valley and Ponte Vedra Beach, that permit comes from St. Johns County Building Services. The City of St. Augustine has its own building department.
We pull the permit and schedule the inspection, so the work is on record. That record matters if you sell the house or file an insurance claim.
Picking the Right One for Your Home
- Want power without thinking about it? An automatic switch with a standby generator.
- Want the essentials running and a lower cost? A manual switch with a portable generator.
- Have a compatible panel and a portable generator? An interlock kit can work.
- Panel full or old? Plan on a panel upgrade first. Our post on storm season electrical prep covers what else to check.
Hurricane season runs through November 30, so the next few weeks are a quiet time to plan. Our post on backup power and surge protection explains how the pieces fit together. Send us a photo of your panel and we will tell you which setup it can take.
Need help with this? See our generac generators or call (904) 837-0310.
