Portable generators are widely used as a home backup power source. However, many people are unaware of the issues that can arise from an improper installation, and notably the dangers linked to backfeeding.
The versatility, convenience and ease of use of portable generators do not come without their own safety aspects. No matter how handy or high quality a generator is, never forget that electricity production is not to be messed with and, if misused, can potentially cause a lot of harm.
This article will explain what backfeeding is and how it occurs, present the dangers it can represent, and give indications on safety measures that can (and should) be taken.
What is Backfeeding?
Backfeeding is a flow of electric energy in the reverse direction of a circuit’s design, from the circuit to the source.
To elaborate, let’s consider a home circuit in the following scenario. Normally, a power grid is the main source of electricity, which flows from the grid to the home circuit via utility lines.
Storms can easily bring power lines down and create power outages
During a power outage, the electricity from the grid is not available. Therefore, a generator is connected to the home circuit to supply power. But the home circuit is already connected to the grid. Therefore, the generator now powers up the home circuit, but also sends power back to the grid.
The former “normal” operation corresponds to the normal flow, for which both the circuit and the grid are designed. While during the outage, there is a reversal in the flow of electricity i.e., from the home circuit back to the grid.
This reversal of the electric energy flow is called “Backfeeding.”
While technically the term only serves to describe a flow of electric energy from the circuit to the source, it is often used as slang to describe the use of an alternative power source (a generator) in their home circuit, even while disconnected from the grid (which prevents its backfeeding). This is why you may find articles such as “How to safely backfeed…”, or phrases such as “Backfeeding a house…”
Dangers Associated With Backfeeding
You may electrocute people working on restoring power
Backfeeding a power grid in such a way is not only illegal in most countries, but also very dangerous. It can cause serious harm to you, your neighbors, and the utility workers working to restore electricity.
If backfed, the power lines are re-energized by the generator. Thus, anyone in contact with the power line is at a high risk of an electric shock. This electric shock can cause a severe injury or even electrocution.
Also, if the power comes back and the generator is still connected, there will be two power sources now connected to your home circuit. This puts a lot of strain on the generator and the home panel, which may catch on fire.
Safety Measures Against Backfeeding
Use a transfer switch to safely power your home circuit
Backfeeding is a dangerous process. If anything goes bad, it can pose a serious threat not only to you, but also to your neighbors and utility workers. Therefore, special care must be taken while using a generator to power a home circuit.
Large permanent generators are preferred to power up a house. These can be installed permanently by means of a transfer switch. The transfer switch isolates the main circuit from the generator. Thus, prevents backfeeding. You can either use a manual or an automatic transfer switch for this purpose.
Portable generators, on the other hand, are not usually meant to power up an entire house. Most are fairly small and geared towards recreational or DIY activities. Although some powerful portable generators exist, many lack necessary power and are not designed to be installed permanently, as their biggest advantage is their portability.
So, in case of a small portable generator, it is better to mount the appliances directly onto the generator (with a properly rated extension cord – do not plug your appliance cord directly). However, if you have a large enough portable generator and you want to connect it to your home circuit, you must connect it by means of a transfer switch.
Please note that the connections of the generator shall only be done by a trained professional.
Is it possible to plug a portable generator directly into a wall outlet?
Male to male cords should never be used
A simple answer to this question would be yes, it’s possible, but NO, you shouldn’t do it!
First, to plug your generator into the wall outlet, you need a male to male cord (having both male ends). A male to male cord is very dangerous as both its ends are open. If anyone accidentally touches one end of the cord while the other end is plugged into the generator, it can cause electrocution of that person.
Furthermore, the wall outlet is connected to the main circuit and the main circuit is further connected to the grid at the home panel. Thus, the power supplied by the generator will also backfeed the grid. And we already know how dangerous backfeeding can be!
Conclusion
Powering a home by a portable generator is a popular practice. However, proper precautionary measures must be taken when doing so to prevent backfeeding.
Powering a home circuit via a portable generator should only be done by the means of an automatic or manual transfer switch. If you do not have a transfer switch, but wish to power your home appliances, you should mount them directly onto the generator, via a properly rated extension lead.
The installation of a portable generator on a home circuit should only be done by a trained professional. Under no circumstance, one should try and connect a generator to the home circuit by himself. This could result in backfeeding, which can be extremely dangerous.
Do you use your portable generator as backup power source for your home? Do you do it via a transfer switch? Are you aware of the risks associated with backfeeding? Let us know in the comments below.
I have watched dozens of Youtube videos on “how to power your whole house with a portable generator.” The majority of them describe the usual options of transfer switches or a dedicated circuit breaker with an interlock plate, and they strongly advise against backfeeding your panel through an existing 240v receptacle with a “suicide cord.”
Then there are the videos specifically teaching us how to make and use a “suicide cord.” To their credit, they all strongly caution that the main breaker must be turned off before such cord is connected.
Even utility companies, while strongly recommending against suicide cords, admit that their use is common. Humans being subject to error, you would think that stories about linemen being injured or killed by backfed power would be a thing. Yet I have never encountered such a story.
My guess is that anyone who inadvertently backfeeds the grid with an improper generator connection would immediately overload their generator and cause the breaker to trip, nullifying the threat. I’m open to edification by qualified utility company personnel.
Not an electrician, but I believe you’d only overload the generator if the power lines have a connection to other homes with appliances plugged in and drawing current. If the power lines are cut leading from the power lines to your home you’d have a live wire outside not drawing power, but ready to electrocute someone. Same if you’re connected to a few other homes but they aren’t drawing much power… or have their main breakers off because they’re also running generators. In any case, turning on the generator with someone touching the line, that person might well be the path of least resistance, especially with the voltage boost. You don’t hear about linemen getting electrocuted this way, because if they do their job right, they’ll disconnect the power on both sides of where they’re working and ground everything out properly to make it safe. If they forget and you switch on that generator, bad news.
I’m not an electrician and this reply probably has errors. Don’t rely on it. Err on the side of caution.