Backfeeding a generator can be dangerous if you don’t know what you’re doing.
Our article provides clear, concise information on what backfeeding is and the risks involved. We also provide helpful diagrams to help you understand the process.
We want our readers to be safe, so we provide solutions on how to stop your generator from backfeeding and prevent it from happening in the first place.
Please take a moment to read our article and share it with your friends!
What is backfeeding a generator?
Backfeeding in any electrical circuit is defined as the electric energy flow in a direction opposite to that intended in the design of the circuit. This can happen in power distribution if two or more sources are available to feed power in the “Mains” and “Standby” configurations without proper interlocks and protection.
Consider the following scenario. Normally, you receive the utility power to your house through the incoming power lines connected to the power grid. This power is received at the main electrical panel of your home’s electrical system, protected by the main breaker.
It is distributed to the home through home circuits connected to electrical appliances, convenience outlets, and the lighting system. Each home circuit is protected by a corresponding branch circuit breaker. This is the normal flow of power into your house, and the complete electrical system is designed to cater to this arrangement.
Suppose a power outage has occurred, mandating the use of a portable generator to provide power to your home. If you just connect an extension cord from the generator to a wall outlet without isolating the main circuit breaker, generator power will flow back to the grid through the utility power line. This reverse flow of electrical power against the design intent is known as backfeeding.
In common parlance, the term backfeeding is used in many ways, which can be a source of confusion if you read various articles on the net. Some even go to the extent of calling for the use of any type of alternative power backfeeding. Hence, terms like “safely backfeeding” or “how to backfeed” should not be taken literally to mean that. You will have an in-depth understanding of the subject by the end of this article to understand the incorrect use of such phrases.
What Are the Different Kinds of Backfeeding?
Back feeding is classified into three categories as explained below,
- Intentional backfeeding – Utilities in some countries allow the consumers to feed back any surplus renewable energy generated to the grid. This happens with proper license, metering, synchronization, and electrical protection systems in place to disconnect the feeding power source when power outages occur. The consumers receive a reduction in their payments based on the readings on the meters. As stated above, this is also called feeding back or intentional backfeeding, as a design intent is involved to send power to the grid.
- Unintentional backfeeding – This has been discussed above, where the power gets supplied in a direction opposite to the intended normal power flow.
- Intrinsic backfeeding – This is not relevant for portable generators and applies only for very big units requiring auxiliary systems like cooling water pumps, control panels, other HVAC equipment, etc.
What Risks Are Involved With Back Feeding?
Your household circuits have 15 or 20 A convenience outlets fed power at 120 V and appliance outlets with a current rating of 30A, 40A, or 50A powered with 240V supply. The dryer outlet is usually rated at 30A and the electric cooking range appliance outlet at 50A.
These outlets are normally connected by extension cords from the portable generator directly to feed power to the entire home. This is done through homemade male cords, many times referred to as the “Suicide Cord” or the “Generator Backfeed Cord.” Each suicide cord is fitted with two male plugs on each end.
What happens if you plug a generator into an outlet?
The power from the generator goes through the concerned branch circuit breaker, energizes the home’s electrical panel, and feeds power to the other home circuits through their respective branch circuit breakers. The dangers involved with such an arrangement are:
- As the main power panel is energized, it can backfeed power to the utility lines connected to it. These utility lines are also connected to your neighbor’s house and other substations with power transformers that may step up the voltage and energize connected high-voltage lines. It is very likely that some maintenance worker is attending to the fault on the same line to restore the power and may end up receiving an electric shock that may prove fatal.
- Backfeeding power to the utility lines can be avoided by opening the main circuit breaker on your electrical panel. But, this is not a reliable and foolproof method as you can easily forget to open the main CB, or somebody can unknowingly again switch it “ON.”
- With this method, you are energizing all the loads connected to your electric panel without any consideration of the generator load. This may overload the generator leading to overheating and frequent trippings.
- The branch circuit breaker that receives power from the outlet connected to the generator and distributes it to the other breakers may not be equipped to sense reverse power flow and overload in the reverse direction. As a result, it may not trip even on overload, even though the entire circuit and its cords are overloaded, feeding power to all of the circuits. This may lead to fire and other safety concerns.
- Most of the time, the circuits in our own wiring are not balanced, with one circuit carrying a much higher current than the other. The only way to cater to such a scenario is to size your generator according to the highest unbalanced load on your circuits. It is always better to distribute the loads equally, taking particular care that all the essential circuits end up in equal proportion on both circuits.
- Last but not least, it can endanger your and your family member’s safety if the grid power resumes while you are backfeeding, causing a heavy short-circuit that may damage your house wiring and/or your generator. Read through this very detailed article on a similar incident and its repercussions.
Is Backfeeding a Generator Illegal?
Yes, backfeeding is illegal in most areas due to the simple reason that it has the potential to cause electrocution and death, and safety measures must be put in place to avoid it.
- This dangerous practice violates the NEC code, and if, God forbid, any electrocution happens, you will be liable for criminal prosecution.
- The power company can impose fines if backfeeding comes to your notice, even if no untoward incident has happened.
- You can be fined by the community or any other authority with powers.
- This may impact the validity of your homeowner’s insurance policy.
Why Do People Backfeed if it is Illegal?
The majority of the incidents or accidents happen due to two reasons universally – Ignorance or lack of knowledge and Overconfidence or perceived expertise.
- The first case relates to ignorance, where you do not have adequate knowledge to carry out a particular task but are forced to do it due to circumstances. Or you might have seen someone do it a few times without any adverse consequences.
- In the second scenario, you are aware and have been doing it correctly in the past, but again certain circumstances make you do things in a way where you feel the probability of something going wrong is slow. This is what happened in the case presented earlier.
How to Stop Your Generator from Backfeeding?
By now, the dangers associated with backfeeding the power from your small generator will be clear to you, and you will take all the steps needed to prevent it. Let us discuss them in detail.
Electrical backfeed prevention
The only way to rule out backfeeding is by ensuring a physical disconnection from the mains or using mechanical interlocks that will not simultaneously allow utility and generator power to come “ON.” Some of the methods to ensure this are:
- Disconnect the wiring: If at all you are still going to use a corded system, disconnect the wiring of that appliance from the circuit wiring and directly connect the generator cord to it. This is a very tedious method and should be used rarely, in exceptional emergencies at the house.
- Using an interlock kit: You can modify your breaker panel and retrofit the interlock kit. The kit is made up of sliding plates to ensure that the main breaker and the generator breaker do not get activated simultaneously. You need to provide an outdoor type power inlet box and a double pole breaker in the generator line. You need to ensure that the interlock kit is compatible with your existing breaker system and preferably of the same make.
- Using the manual transfer switches – The safest method to work with portable generators is to install a transfer switch that has two numbers of double pole breakers and an interlocking mechanism to allow the closing of only one breaker at a given time. If the generator rating allows, you can power your entire house. Otherwise, you need a service panel to switch on only the essential loads when the power outage occurs, while other loads connected to the main panel remain off. We have covered all the nuances and benefits of a properly installed transfer switch in our detailed article on the subject.
- Using an Automatic Transfer Switch (ATS) – If a standby generator is used to power your whole house, ATS automatically isolates the grid power before starting the generator.
Installation of all the three systems mentioned above should be carried out by a professional electrician qualified to do the job. In addition, these systems require a permit from the relevant authorities.
How to Determine the Manual Transfer Switch Size
We have covered this topic in detail in our article on Manual Transfer Switches.
Backfeeding a generator is the process of feeding electricity from the generator back into the electrical grid. While backfeeding a generator is illegal in many places, there are still people who do it. As explained above, backfeeding can have disastrous consequences such as electrocution, fire, damage to your equipment, criminal prosecution, and danger to your own life. This should be avoided under all circumstances.
If you have any questions or clarifications about the above blog post, feel free to respond in the comments section below, and I will try my best to reply ASAP.