An important consideration in the installation of a home backup power supply, whether provided by a portable or permanent standby generator, is how the generator connects from the electrical grid to the home's electrical panel. When the power from the electrical grid goes down the power must be switched, or transfered, to the generator. When power is restored, the power must be safely switched from the generator back to the electrical grid.
See related: The Basics of Generator Transfer Switches
There are two common approaches to connecting a generator:
Generator Interlock KitA generator interlock is a device that prevents the main breaker and the generator breaker from being turned on at the same time. It is installed on the front of the home's breaker panel, allowing a generator to power multiple circuits in your house. The number of circuits powered must not exceed the capacity of the generator.
When installing a generator interlock kit additional modifications may be needed within the electrical panel, including having enough circuit breaker spaces inside the panel.
Because there is nothing to prevent additional breakers from being activated, there is a risk of overloading and damaging the backup generator.
Automatic Transfer Switch (ATS)An automatic transfer switch is dedicated to each circuit breaker and can operate multiple circuits at once. This gives you the flexibility of safely powering a couple of appliances, or your entire home.
Unlike a generator unlock, which requires manual intervention to switch the power source, an automatic transfer switch, as the name implies, does this job automatically in just a matter of seconds.
Importantly, a transfer switch can monitor the line for surges and unexpected spikes in the electrical grid, preventing unsafe surges that could damage the generator or your home. Another feature of transfer switches is load management, which ensures ensures that high-powered appliances do not draw too much power from the generator, which could create an electrical hazard.
Both transfer switches and interlock kits should be installed by a licensed electrician.
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