Generator Inlet Box: Installation Basics
A generator power inlet box is the weatherproof plug mounted on the outside of your house where the generator cord connects. Wires run from it to an interlocked breaker or a transfer switch inside, so the generator feeds your panel through one cord and never through a wall outlet.
What the inlet box does
The inlet has male prongs. Your generator cord has a female connector on the house end, so with the cord unplugged there's nothing live to touch. That's the whole point of the design, and it's why a properly wired inlet is safe while a "suicide cord" into a dryer outlet is not.
On its own the inlet does nothing. It has to land on one of two things inside:
- A back-fed two-pole breaker in your main panel, locked out by an interlock kit so the generator breaker and the utility main can't both be on.
- A manual transfer switch that moves chosen circuits to generator power.
Amp ratings and plug types
Match the inlet to the biggest outlet on your generator. Generac's HomeLink kits show the two common pairings.
| Rating | Inlet on the house | Cord Generac pairs with it | Enclosure |
|---|---|---|---|
| 30 amp | L14-30 | 10 ft, 10/4, L14-30 male and female | NEMA 3R, resin or aluminum |
| 50 amp | CS6377 | 10 ft, 6/4, CS6364 female to NEMA 14-50 male | NEMA 3R, aluminum |
The 30-amp HomeLink switches are made for generators with an L14-30R outlet, and the 50-amp switches for generators with a 14-50R outlet. Generac says both resin and aluminum inlet boxes are available. Either works outdoors; what matters is the amp rating and a cover that closes over the plug.
Some setups skip the inlet entirely. Generac's 30-amp 1-2 circuit switch and its whole-house 200-amp utility switch with a 50-amp generator side let the cord plug straight into the bottom of the switch, for outdoor installs only.
Where it goes
Pick the spot with the generator in mind, not the panel. The generator has to sit outdoors at least 20 feet from doors, windows and vents, and the cord that comes in a HomeLink bundle is 10 feet long. Put the inlet on a wall with no windows nearby, or plan on a longer cord rated for the same amps.
Other things your electrician will look at:
- A short, clean run back to the panel or transfer switch.
- A spot that's easy to reach in snow and dark, at a height you can plug into without kneeling in a puddle.
- Somewhere the cord won't cross a driveway or a doorway.
Tools and parts
- The inlet box, matched to your generator's outlet.
- Conduit and fittings. HomeLink kits use 1-inch ENT on 30-amp models and 1-1/4-inch ENT on 50-amp models.
- Wire sized by your electrician for the inlet's rating and the run length.
- The two-pole generator breaker and the interlock kit, or the transfer switch.
- A cord with ends that match both the generator and the inlet.
How the installation goes
The electrician confirms your generator's outlet type and the panel's interlock options.
Permit. Check with your local building department before any work starts.
The inlet goes on the outside wall, and conduit runs to the panel or transfer switch.
Wire is pulled and landed on the inlet terminals and the back-fed breaker or switch.
The interlock plate or transfer switch goes on, and the breaker gets a clear label.
Inspection, then a live test with the generator running.
Mistakes to avoid
- A female receptacle on the outside wall. That would leave live prongs on your cord; inlets are male for a reason.
- Mismatched ratings. A small inlet on a big generator caps you at the inlet's rating, and an adapter doesn't change that.
- An inlet under a window, which pulls the generator's exhaust toward the house.
- Skipping the interlock. An inlet on a back-fed breaker with no lockout is a backfeed waiting to happen.
FAQ
What happens if you plug a generator into a house outlet?
You backfeed the house wiring and, through it, the utility line. CPSC warns that plugging a generator into a wall outlet can electrocute utility workers and neighbors.
Can you plug a 30 amp generator into a 50 amp outlet?
The plugs don't match, so it takes an adapter cord, and Generac's 30-amp and 50-amp kits use different connectors at each end. Even with an adapter, you only get what the generator and its breaker can deliver. Ask your electrician before you buy one.
Is backfeeding a generator illegal?
Rules vary by state and town, so check with your local building department and utility. The safety advice doesn't vary: never connect a generator to household wiring without a transfer switch. An inspected interlock or transfer switch is the legal and safe way.
How do you install a generator plug to a breaker box?
The inlet box mounts outside, a conduit run connects it to a two-pole breaker in your panel, and an interlock kit locks that breaker against the main. It's licensed electrician work with a permit and inspection.
Sources
- GeneracHomeLink Manual Transfer Switch spec sheet (6852, 6853, 6854, 9854, 9855) (opens in a new tab)
- U.S. Consumer Product Safety CommissionPortable Generator Safety Alert (opens in a new tab)
- South Carolina State FireGenerator Safety (opens in a new tab)
- Schneider ElectricHow does the QO / Homeline generator interlock kit work? (FA102367) (opens in a new tab)
- GeneracWhole House 200A Utility / 50A Generator Manual Transfer Switch (opens in a new tab)
- Generac30-Amp 1-2 Circuit Manual Transfer Switch (opens in a new tab)
- GeneracAbout Portable Transfer Switches (HomeLink) (opens in a new tab)