Are Generator Interlock Kits Legal?

Today, we’re answering an important question for anyone living in an area that sees a lot or power outages: are generator interlock kits legal?

Your power never goes out at a convenient time. Not only does power keep your home’s temperature regulated, but it runs your refrigerator, too. In some cases, it will also help keep any necessary medical devices on. The bottom line is you need reliable power to keep your home running smoothly.

So, what do you do if your power goes out? The best option for anyone who experiences frequent power outages and does not have a permanent standby generator is to purchase either a transfer switch or a generator interlock kit. The problem with transfer switches is that they are expensive, leaving a generator interlock kit as your best option.

Generator interlock kits come with many regulations but are legal in the United States as long as you follow all codes that protect against over-currents and have a functioning backup system that can support the backup generator. In some jurisdictions, you may need a professional to do the work, so you should make sure you can install it on your own.

This article will cover what a generator interlock kit is, how it compares to a transfer switch, and how to install one. Additionally, we will talk about the electrical codes involved and what you need to know before deciding to use one.

Generator interlock kits are devices designed to power a home through a portable generator during a power outage safely by connecting the generator to the existing electrical system. It is an affordable alternative to a transfer switch.

An interlock kit prevents the main breaker on your electrical control panel from being turned on at the same time as your generator breaker. It makes it so you cannot operate your panel’s main cutoff switch. When you are using your generator, it also prevents power from being back-fed into the power lines. This is important because it can injure whoever is working to repair your mainline power.

In generator mode, the back feed breaker is on. This means that it is accepting power from the generator into the panel. In this case, though, the main breaker is off, which keeps the external mains separate. At this point, you’ll be able to turn on any individual breakers you need. The only one that must stay off is the main breaker.

Once power is restored, all you have to do is turn off the individual breakers and slide the interlock kit back down to cover the generator breaker. This will expose the main breaker once more. After turning that back on, you can turn on each breaker once more. Be sure to unplug the generator power cord and return the generator once you’re done using it.

Also known as an automatic transfer switch, these devices transfer power supply. They take power from its primary source to a backup generator through a separate set of circuit breaker switches. These devices activate when they sense a power outage or failure in the primary source.

By flipping the switches you can isolate entire circuits from the main breaker and into the generator. Although transfer switches are beneficial, they are also very expensive and more difficult to install.

This code requires that the standby or backup system can support the selected loads. These loads are in accordance with the amount of power that needs to be maintained by the backup generator. Standby electrical systems have the option to include legal systems, optional standby systems, and backup systems. Although both legal and optional standby systems are included in the NEC Chapter 7 Articles 701 and 702, backup systems are not.

In order to be up to code, your generator interlock kit must allow only one of the breakers to be in the “ON” position at one time. This meets the requirements of Article 702 of the National Electrical Code ANSI/NFPA 70.

Specifically, electrical panelboards must be protected from over-currents by a single device. This must be either be located ahead of the panelboard, within the panel board, or at any point on the supply side of the panelboard.

One specific section is good to note:

“Each lighting and appliance branch-circuit panelboard shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard.” – US NEC 408.36

As long as you install the breaker retaining strap, you will appropriately meet the requirements of Article 408.36.

You should have two decal stickers, one is a yellow one, and the other is white. The yellow is the operating instructions, while the white one helps you identify the manually interlocked breaker. You should put the instructions on the door to the panel cover, so they’re easily readable. Place the white sticker next to the interlocked breaker.

If you’d rather, you can always trip the bottom part off so that you can stick the decal onto the breaker itself. However, this is entirely up to you. Next to the breaker will work just fine.