How to hook up generator to house

We generally take the convenience of electricity for granted. The juice that runs in the electrical veins is our lifeblood, too.

We’ve all been without electricity, and it isn’t pretty. We flick that switch ten times even though we’re fully aware the power’s out. It fuels everything from our light, internet, and well-being, yet most of us are usually unsure how to select and connect a generator to our house.

If you have decided to use generator power during power outages, It is essential for you to learn “how to hook up generator to house” in the event of power loss. Before you connect a generator to the house, you must familiarise yourself with the nuances of selecting, purchasing, and getting the generator connected to the house.

In essence, the entire process can be divided into two phases – the planning and actual execution. By the end of this article, you will get the hang of both of these phases.

The Planning Phase

In the planning phase, you should

• Determine the essential appliances that you plan to use during a power outage.
• Work out the total power requirement for these essential appliances and their starting and running wattages.
• Decide upon the type of generator required. This involves the choice between a portable generator, inverter, or a standby generator, consideration of various factors like the fuel used, selection of a particular brand, fuel storage requirements, budget, etc.
• Choose an electrical wiring system out of a cord and plug system, interlock kit, manual transfer switch, or automatic transfer switch, and learn how to connect a generator to the house using them.
• Choose the correct location for placing the generator during operation to avoid carbon monoxide poisoning from the exhaust, to ensure safety from any fire Hazard or explosion, and to protect the generator and its wiring from the elements.
• Ensure proper earthing and grounding of the generator system.

You can learn about the different aspects listed above in our separate detailed articles. In this article, you will familiarise yourself with all the important aspects related to Point No. 4 to enable you to connect your selected portable generator to your house.

Understanding the American Home Wiring System

Before deep-diving into systems to connect a generator to a house, you must review and understand the configuration of the common American home wiring system. The configuration of the home wiring affects the size and the connection to the generator.

The system follows 3-wire 120/240 V wiring with two separate 120 V lines with a common neutral connected to 2 bus bars In your main electrical panel. The small electrical loads throughout the house are distributed between these two 120 V lines, whereas the larger appliances like central A/C draw power supply from both lines. The wiring also contains a ground wire for electrical safety.

To energize the entire house during a power outage through portable generators, the generator must be able to provide a dual 120 V/240 V electrical power supply. Most smaller Inverter generators have only 120 V power outlets and can’t power your entire home.

How to Connect Generator to House

As indicated above, there are multiple ways to connect your portable generator to the house. These methods range from simple extension cords to automatic transfer switches with increasing electrical safety and convenience at the expense of additional costs. Let us familiarise you with each of these methods in detail.

Cord and Plug System

The simplest method is to hook up a generator directly to your AC loads using extension cords, known as the cord and plug system. All the generators have standard 120 V outlets. You just need to plugin three-wire cables into these outlets and connect them to the appliances you want to power.

It is quite common to run these cables through open doors and windows, but you must take care to use heavy-duty outdoor-rated cables only. The size of the cable will depend on the load current and its length. To power loads up to 20 A, you can use a #12 AWG cord.

Most generator models above 4 kW rating have at least one NEMA 120/240 output using a 30 or 50 Amps rated four-hole twist-lock receptacle. You can use this receptacle to connect a special 4 – wire generator cord having multiple outlets at the load end.

While the cord and plug system provides a quick solution during an emergency, it poses a problem to switch on power to anything directly connected to your home wiring. You may need to disconnect these loads from your electrical system before connecting them to an extension cord and reconnect them back when your main power resumes. The whole process has to be repeated for every power outage.

Using a pre-wired generator transfer switch is a much better and safer method to hook up generator power to your house. It allows you to receive power from a utility line or the generator and prevents accidental backfeeding.

Corded vs. Power Transfer System

As discussed above, corded means using an extension cord and plugging each appliance into a power source. Once everything is connected, the generator will provide the power.

Pros:

• It may seem easy to manage
• No complicated transfer system to install
• For the do-it-yourself person
• Ideal for sporadic power outages

Cons:

• Requires multiple cords
• Tripping hazard
• Limited outlets
• Can overburden the generator and can’t use full generator power

A power transfer switch or system means that a simple switch will have the house up and running if you lose connection to the power grid.

Pros:

• A flip of the switch activates power from the main breakers 
• No messy or tangled cords
• Anyone can activate it
• Efficient

Cons: 

• Requires professional installation (in most cases)
• Costs more money

Using an Interlock Kit

If you do not want to spend too much, you can simply retrofit the transfer equipment to your existing breaker box using a mechanical interlock. This interlock comprises slide plates to ensure that your main circuit breaker and the generator breaker will not get activated simultaneously.

In addition, you will require an outdoor type of power inlet box and a double pole circuit breaker in the generator line. You should ensure that the kit is compatible with your specific breaker box and breakers. The interlock has to be designed for the brand of your existing system.

The connection, of course, must be done by a licensed electrician and requires a permit from the relevant authorities before you can use it.

Pros

• Lower cost
• Supplies power to the entire house.
• No rewiring of the existing circuits.

Cons

• Your service box must have available slots below the main breaker.
• If the box lacks enough free spaces, you must add piggyback breakers.
• You may have to relocate some of your existing branch circuits.
• Interlock must be designed specifically for the brand of your existing system.
• You may overload your generator if you do not properly study the current requirement of your existing electrical devices.

The transfer procedure using the interlock kit is as follows:

• Switch on your generator and warm it.
• Turn off your main circuit breaker and other individual outlet breakers.
• Slide your mechanical interlock plate.
• Connect the generator cord to the inlet plug and turn on the generator breaker.
• Switch on individual load breakers one by one, ensuring you do not overload the generator.
• Follow the reverse sequence when the utility power is restored.

So far, we have covered the cases where you will connect a portable generator to a house without a transfer switch. Let us now learn how to use different types of transfer switches and the advantages offered by them.

Transfer Switches for the Entire House

You can define a manual transfer switch as a system of two numbers of double pole breakers with a locking mechanism to allow the activation of only one circuit breaker at a time. You will have to manually operate the manual transfer switches during a power supply failure to connect your appliances to the generator.

Depending on your generator power rating, you can either switch on the power to the entire house or may need to keep some breakers in the Off position. If the main breaker and the individual load breakers are situated in different panels or if your main panel does not have space or provision to install the extra double pole breaker with an interlock system discussed above, you will have to break the connection between the main breaker and distribution system and install the manual transfer switch between the two.

This option has a higher cost than the interlock kit and requires some additional wiring work to install the transfer switch before the load breakers. Also, you may overload your backup generator if you are not careful. The sequence to carry out the generator house hookup with this option is as follows:

• Switch on and warm up your generator.
• Ensure all the breakers in the main breaker box, including the load breakers, are in off condition.
• Connect the generator to the generator inlet plug using a generator cord.
• Operate the installed transfer switch to “generator position” from “line.”
• Turn on the individual breakers one at a time to avoid overloading the generator circuit.

Using a Sub-Panel for Essential Lines

This is convenient if you have decided to switch only the selected essential loads during the blackout. This avoids generator overloading, and you do not have to operate individual breakers. You must provide an additional sub-panel containing the generator transfer switch and individual circuit breakers for the selected line. The option is undoubtedly more expensive than the other options discussed.

A qualified electrician must carry out the electrical work to relocate these selected lines from the main breaker box to the sub panel and provide a separate breaker in the main breaker box to feed power to the sub panel. In addition, you should obtain the necessary permits from your utility company.

When the main power is available, the essential loads will be powered through the transfer box while other loads are fed from the main breaker box. The procedure to hook up a generator during the blackout is as given below:

• Move the interlock transfer switch in the subpanel and individual breakers to the “off” position.
• Start the generator and connect it with a suitable cord to the power inlet box.
• Move the generator interlock plate to the correct position and switch on the generator circuit breaker when the generator has warmed up.
• Turn on the individual breakers one at a time to feed essential lines.

The services connected to the main breaker box will remain de-energized during the blackout. When the normal supply resumes, the connecting appliances will turn on and alert you to restore power from the utility lines. The arrangement ensures the isolation of the essential lines from the mains with the interlock mechanism, thereby eliminating any possibility of back feeding.

Automatic Transfer Switches

if you want the convenience of a completely intervention-free automatic operation and are willing to spend around $ 10,000, you can go in for a standby generator with an automatic transfer panel. These generators, also known as whole house generators, are connected to the fuel lines you use for heating your house.

The whole house generator is hardwired to the transfer switch panel and includes the control wiring circuits. The transfer panel permanently connects the utility lines and your house wiring. This transfer switch is designed to automatically detect the power outage and isolate your entire electrical wiring or designated essential lines from the grid power.

It then starts the generator and connects it to the emergency circuits. On restoring the grid voltage, the transfer switch will connect you back to the utility and automatically switch the generator off. The typical transfer time of an automatic system is 10 to 30 seconds. You will still require a UPS if you want uninterrupted power to your electronic devices to prevent data loss.

You can fuel some expensive portable generators in a higher power rating range from external fuel lines. These machines can be automatically operated like whole house generators. The system requires professional installation and relevant permits from utility agencies.

Universal transfer switches (UTS)

A universal transfer switch is a user-programmable power management device that allows you to determine the home circuits you wish to feed or shut down through pre-programmed priorities. Unlike other transfer switch options that only work with the generator sets, the UTS can be configured for use with a UPS, battery backup, and even other sources like solar panels.

The intelligent power management feature of the universal transfer switches prevents the generator from overloading, eliminates the need for a separate subpanel to feed the essential lines, and allows easy power management.

Generator Set-Up Safety

Electricity is a silent resource despite being a dangerous element. No one thinks about it until it goes out, or perhaps when that nasty utility bill arrives in the mail.

Having a reliable generator to operate your appliance during power outages requires serious safety precautions.

Carbon monoxide poisoning, electrocution, and fire hazards are real concerns when operating a generator. Hooking up a generator to a house isn’t a simple process.

Carbon Monoxide Poisoning

Don’t be one of those people who don’t wake up in the morning because of carbon monoxide poisoning, which is entirely preventable. This point can’t be stressed enough and is an essential step in deciding the generator’s location.

The exhaust emitted by a generator is toxic carbon monoxide. It is invisible, odorless, and can kill in minutes.

Follow these safety instructions:

1. Place the generator outside and away from windows, doors, and vents to avoid sucking the fumes inside
2. A running generator does not belong in a garage, basement, home interior, attic, or crawlspace. Learn how to build a generator shed in the video below
3. If you accidentally inhale carbon monoxide, get fresh air immediately. Consult a medical professional if you suspect CO poisoning

CO poisoning is serious. Monitor your symptoms if you experience headaches, fatigue, shortness of breath, dizziness, and nausea. Seek a medical professional for advice. Prolonged exposure to CO will lead to losing motor functions, unconsciousness, and even death.

Electrocution

Most people don’t realize that a generator has enough electrical power to inflict severe shock and electrocution if not used properly.

A generator must be kept dry. Use caution during wet weather, near a swimming pool, or a garden sprinkler.

Install your generator correctly, or backfeeding will feed the current into utility lines and potentially harm utility workers or family members. A generator connected to a building must isolate the power and comply with local laws and electrical codes.

Safe Use Of Cords

• An important safety tip is to use a proper electrical cord that isn’t damaged. Use polarized or three-prong plugs. A safe cord is free of cuts and shows no exposed wires.
• A shorter cable can distribute the power better than a longer version, and the thickness of a cable also indicates how much electrical current a cord can manage. If the wires inside are larger and the cord contains fewer strands, the more power the cord can handle.
• A tip for when you need to extend that extension cord and you’re using a 16 gauge cord; the next cord should be a 14 gauge cord (cord power numbers go down instead of up; therefore, 14 gauge has a larger power capacity).
• Connect multiple appliances and run one cord from the generator using a designated PowerBar, OR:
• Connect multiple appliances with several extension cords from the outside
• The best option is to run one cord per outlet on the generator (4 outlets, 4 cords)
• Power up the generator following manual instructions, and before you start the generator, disconnect all cords. Some may find it surprising that a generator and your appliance should not be connected at startup. Start the generator before connecting it to your home or your appliances, as you don’t want the electrical load to burden the generator.

Conclusion

Investing in a generator isn’t an easy fix. Instead, it is a long-term investment in your safety and well-being.

Let us know if this article helped you get started on choosing the right generator by commenting below or sharing with friends.