Never Backfeed a House with a Portable Generator
Electricity comes into a home from the utility via a transformer. The transformer lowers the voltage from thousands of volts down to 240 volts before it enters the home. In the home, it passes through the main circuit breaker for distribution through branch circuit breakers to various appliances, lighting, and convenience outlets.
Convenience outlets in the home supply 120 volts with a maximum amperage of 15 or 20 amps. Some appliance outlets for electric ranges or electric dryers supply 240 volts at 30, 40 or even 50 amperes.
Backfeeding is the practice of powering a home with a portable generator during a power outage by connecting it to an appliance or convenience outlet.
Backfeeding a house, an apartment, or business is a dangerous practice and illegal in some jurisdictions.
People who backfeed their houses connect the generator to an outlet with a homemade cord fitted with two male plugs. With a Generator Backfeed Cord, sometimes called a suicide cord, electrical power enters the main panel through the outlet’s branch circuit breaker. The panel distributes the power to the rest of the house through the other branch circuit breakers. It also feeds power out through the main breaker to the transformer, which then converts it back to thousands of volts and attempts to energize all neighborhood utility lines.
Energizing the utility lines in this fashion is dangerous and illegal. Workers attempting to restore power to the neighborhood may unexpectedly encounter high voltage on the utility lines and suffer a fatal shock.
Turning off the main breaker alleviates the hazard, but doing so relies on someone to shut the main breaker off. There is no guarantee that someone else will not turn the main breaker back on and energize the neighborhood wires. This arrangement provides no safeguards against accidentally energizing the utility lines or introducing a electrocution hazard in the home.
A Generator Backfeed cord introduces electrocution hazard. If the plug inside the house falls out of the appliance outlet, the cord has 240 volts across its terminals. Anyone stumbling onto the cord or tripping over it may receive an electric shock. Thus the aptly named Generator Suicide Cord.
Poor Power Management
Backfeeding a service panel energizes the entire circuit breaker panel. The panel distributes power throughout the house on all circuits. Only the largest portable generators have the power capacity to supply enough power for an entire home. Turning some breakers off helps to resolve this issue but does so without balancing the loads.
The generator supplies 240 volts split between two, 120-volt lines. Each line delivers half the generator’s capacity. If most or all essential circuits end up on the same line, the unbalanced load puts a strain on the generator and the home can only use half the generator’s capacity.
A Better Solution
A manual transfer switch isolates the home electrical system from the utility lines before it connects the power from the generator. The switch distributes power to the branch circuits the homeowner selected during installation. Each circuit has its own breaker, and electrical power can’t leave the dwelling. It won’t power the neighborhood utility lines or endanger workers.
When the utility restores power, the transfer switch protects the generator from damage caused by the sudden introduction of another power source.
The generator load remains balanced because the transfer switch distributes the load equally between the two 120-Volt lines. The balanced load puts less strain on the generator, saves fuel, and allows utilization of the generator’s full capacity.
Backfeeding is a dangerous practice illegal in many localities. If you backfeed your home’s electrical system and injure or kill a worker, you are liable and accountable, and face a very real possibility of criminal prosecution for your actions. Further, even your actions don’t injure anyone, if the utility finds that you are backfeeding their lines, you may be subject to fines or the utility may disconnect your home.
Be safe and avoid problems. Install a manual transfer switch or hire a qualified electrician to do it and be ready for the next power outage. It’s not worth the danger or the risk. A manual transfer switch ensures essentials like refrigerators, furnaces, and sump pumps have power from a safe, reliable connections.
Updated January 29, 2020