How To Wire A Generator To A Breaker Box

When storms or natural disasters rage your area, you’re likely to witness a power outage which means you cannot operate your electrical appliances at that time. It even becomes more convenient for you if you own a standby generator wired directly to your house’s electrical system. In contrast, if you own a portable generator, you will have to figure out how to wire the generator to a breaker box.

While this may sound complicated, with basic electrical handling understanding, most homeowners can comfortably handle it. However, with a generator at hand, you will find relief because you can power your essential electronics, including lighting your home.

Even so, a lot of care should be taken when wiring a generator to your breaker box; a slight mistake can lead to a disaster. And remember it is not advisable to power your house using extension cables. Extension cables are only ideal for powering outdoor activities.

How to Wire a Generator to a Breaker Box Safely.

how to wire a generator to a breaker box

Understand the Voltage of Your Generator

Portable generators can either have a 240, 120 circuit, or both. A 240-volt circuit comes with a couple of wires carrying 120 volts each. There has to be a ground wire that is either coded in green or copper color among the cables. A 240-volt circuit does not have a neutral wire.

The good thing about a 240-volt circuit is it can deliver both 120 and 240 volts. However, a 120 volts circuit cannot deliver 240 volts. Understanding the voltage of your generator is crucial during the wiring of a generator to your breaker box.

Materials You Will Need

To successfully wire your generator to your home’s breaker box, you will require few materials.

  • Voltmeter

How To Wire A Generator To A Breaker Box

  • Double pole breaker– This should have a similar amperage as your generator.

How To Wire A Generator To A Breaker Box

  • Electric cables (eight-by-three wires) are suitable for the 40 amp breaker.

How To Wire A Generator To A Breaker Box

  • Stripper tool

How To Wire A Generator To A Breaker Box

  • A tool kit that has screwdrivers and a pair of pliers

How To Wire A Generator To A Breaker Box

How To Wire A Generator To A Breaker Box

Step#1: Switch off the main power source

The first thing you need to do before working on your breaker box is to terminate your house’s main power supply line. You don’t want the main power line to be restored while you are holding the wires. It can electrocute you to death or even cause a fire.

For safety purposes, counter-check the presence of any power in the breaker panel by using a voltmeter. If there is any flow of electricity in the breaker box, do not use it. Wait until it is completely terminated. And, of course, the generator should also be off.

Step#2: Strip your cables

Using your stripper tool, strip one end of two black cables to the extent it exposes the wires to about half an inch. The stripper tool will make it easy for you to uncover the wires than using a knife or tearing it with your teeth.

Step#3: Screw in your wires

Gradually start screwing in the two stripped black cables into your circuit breaker. A robust flat screwdriver should easily do this. In most cases, circuit breakers have two screws meant to hold the two wires you are driving in firmly. When the wires get to the terminals, tighten them, thereby tightening the screw.

Step#4: Fix the breaker into the service panel

This step requires you to install the breaker into the service panel. Start by identifying where you need the breaker to be positioned while inside the housing of the service panel. Fix it at the preferred position by moving it back and forth till the circuit breaker is firm. This will place the tabbed ending of the circuit breaker in the housing firstly. Then snap the other part of the breaker onto the hot bus bar to finish the installation.

Step#5: Check on your double pole breaker

Look at the positioning of the double pole and ensure that it fits correctly. Remember, the double pole breaker carries 240-volt power, which means it will have double 120-volt live cables totaling up to 240 volts.

Step#6: Work on wiring

The grounding wire should run through the bar. Ensure it runs to the ending of the 240-volt outlet in the breaker box and firmly screw it there. The next step should be inserting the two black cables (eighty-three wires) into the generator’s outlet you desire to connect. At this point, you’ll notice there are three screws: two colorless screws and one green screw. Put in the black cables each on the colorless screws and the grounding wire into the green screw.

It is a critical step that you should do with a lot of care; if you make any error in grounding, it can be disastrous. If you are not at ease with handling wires, this is where you will need a certified electrician.

Step#7: Outlet

After securing the cables in the above procedure, it is now time to attach the receptacles to the wall. Head back to where the main power source supply of your house is and turn it on. Turn on the breaker box switch it on by pushing it to the on the setting.

At this point, you are almost done with wiring your generator to a breaker box of your house. Check on the positioning of the generator and ensure it is not near your windows, vent, or doors.

Ensure the generator’s circuit breakers are off before you start it. Plug your generator on the outlet and power it on. The generator should be able to power your house once it is ready for loading.

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Precautions to observe When Learning How To Wire A Generator To A Breaker Box

You should ensure the two voltage cables (eight-by-three wires) are of the same color code. It is for compliance with the wiring code of the US.

In most cases, the cables can either be black or red. If need be, you can mark them using tapes.

If you are sure that you will be using a 40 amp breaker, you should use the eight-by-three wires.

Sometimes switching off the breakers does not mean you have completely disconnected the main electricity supply line.

Before you start working on the breaker box, ensure a complete termination of electricity by using a voltmeter to ascertain.

Sometimes there could be power that can shock you to death; avoid such.

If you reside in a state that doesn’t allow homeowners to operate the electricity, consult a licensed electrician on how to go about it.

Otherwise, you can be making an illegal connection which may land you in trouble.

Frequently Asked Questions

1.Can I Run My Generator 24/7?

Unless it is a standby generator, the answer is no.

Most portable generator brands require several breaks during the day: they are not designed for 24/7 operation. Therefore, it’s advisable to switch off the generator often during the day to cool down. You can take this opportunity to refuel and check oil levels.

2. Should I Turn off the Main Breaker When Powering the Generator?

Yes. Before you start the generator’s engine, always switch off the unit’s circuit breaker. This is to avoid the drawing of current by the load before the generator is ready for loading. Remember to switch off the breaker before shutting down the generator.

3. What is the meaning of 120/240V in a generator?

This means the generator can produce 120 and 240 volts. Generators with such readings come with a voltage selector, which allows you to choose a voltage production of 120 volts only or 120/240 volts.

The selection of the voltage will depend on the appliance you intend to run. If you connect 240-volt equipment to the 4-prong outlet, the voltage selector switch should be at 120/240V.

4. Can I Connect a 120V into a 240V Outlet Wall?

No, it’s not advisable unless you’re using a power adapter. When you plug a 120V device into a 240V wall socket, you’re likely to damage it because of the high voltage in the 240V outlet. While you can plug some devices in America in either of the sockets without any problem, it’s safe to use a plug adapter.

5. Can I Bypass the Circuit Breaker on My Generator?

Yes, however, you should not do it. The main role of circuit breakers is to stop the current flow should it be more than a specific limit. Bypassing the circuit breaker means your generator or appliances are no longer safe should there be a power surge. And this can easily result in a fire.

6. How can I Tell my Generator is Overloaded?

Overloading a generator can risk your appliances, house, and the generator too. Here are the signs of an overloaded generator;

  • A reduction in power output

Once you note a drop in electricity output from your generator, there is an overload.

This can lead to the poor performance of your generator.

  • The generator overheats and becomes extra noisy

When more power is demanded because of the overload, the generator’s engine will struggle to generate more power, making it loud and hot. The risk of a heated generator can lead to the rising of intermittent power, which can damage any appliances directly connected to the generator. There is also a need to learn why are inverter generators so quiet?


Final word

Wiring a generator to a breaker box by yourself can save you a handsome of dollars, but it is a risky procedure to undertake. It can risk your life, that of your family members, your house, electrical appliances, and the generator itself. If you are not conversant with generator connections, handling wiring, and electrical connections, do not do it. Instead, contact a professional electrician to do it.










About Steve Stuart

Steve Stuart is an electrical engineer who developed interest on generators during his school years. After school, he became a generator enthusiast. This is after encountering power supply problems at the area of residence where he lived. Power would be on and off and so food would go bad and the room heater would go off especially during winter. After trying the different generator brands for several years, Steve now provides information on the available brands and products in the market today. Based on his experience, he gives the do’s and the don’ts when it comes to generator use.

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