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 and is distributed 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.
The practice of powering a home with a portable generator during a power outage by connecting it to an appliance or convenience outlet is called backfeeding.
Backfeeding a house, an apartment, or business is a dangerous practice.
People who backfeed their houses connect the generator to an outlet with a heavy power cord. This allows electrical power to enter 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 thousand 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.
If the main breaker is turned off, it alleviates the hazard, but that requires remembering to shut the breaker off, and relies solely on the user to do so. There is no guarantee that someone else will not turn the main breaker back on and suddenly energize the neighborhood wires. There is no safeguard in this arrangement.
Poor Power Management
Backfeeding a service panel energizes the entire panel and power is distributed throughout the house on all circuits. Only the largest portable generators are capable of supplying 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 which is split into two, 120-volt lines. Each line is capable of supplying half the generators capacity.
If all the essential circuits are located 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 takes power from the generator and distributes it only to the branch circuits that were selected when the switch was installed. Each circuit has its own breaker, and electrical power is automatically confined to the dwelling. It can never accidentally power the neighborhood utility lines and endanger workers.
The load is balanced because half of the load is assigned to one 120-volt line, and the other half is assigned to the second 120-volt line. 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 that is illegal in many localities. If you backfeed your home’s electrical system and injure or kill a worker, you will be held liable and accountable, and more than likely will be criminally prosecuted for your actions. Further, even if no one is injured, 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.