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.
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. 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. 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 from the home circuit back to the grid. This reversal of the electric energy flow is called “backfeeding.”
Dangers Associated with Backfeeding
Backfeeding can cause serious harm to you, your neighbors, and utility workers restoring 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
Special care must be taken while using a generator to power a home circuit.
Large permanent generators are preferred to power a house. These can be installed permanently by means of an automatic or manual transfer switch. The transfer switch isolates the main circuit from the generator and prevents backfeeding.
Portable generators, on the other hand, are not usually meant to power an entire house. Most are fairly small and geared toward 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.
With a small portable generator, it is better to mount the appliances directly onto the generator with a properly rated extension cord — do not plug in your appliance cords directly. However, if you have a large enough portable generator and you want to connect it to your home circuit, an experienced electrician must connect it by means of a transfer switch.
NEVER Plug a Portable Generator Directly into a Wall Outlet
A portable generator cannot be plugged into a wall outlet using safe, commercially available and UL-approved plug-ins. There is a reason for that. Attempting to make your own cord is dangerous and deadly. Furthermore, the wall outlet is connected to the main circuit and the main circuit is 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!
Powering a home by a portable generator is a popular practice. However, powering a home circuit via a portable generator should only be done by the means of an automatic or manual transfer switch and done by an experienced electrician. If you do not have a transfer switch, but wish to power your home appliances, you should use a properly rated extension cord to connect them to the generator.
Source: generatorbible.com, a leader in portable generators stats and comparison tools.