A vital part of any standby generator installation, an automatic transfer switch (ATS) is the brains for backup power to come to life.
Just like your home's thermostat monitors temperature, an ATS monitors utility power. So, when the power goes out, the transfer switch will automatically command the generator to start and backup your house, as if nothing happened at all.
Picking the right transfer switch is simple, just select the size, style, and power management options that will work for your generator and home.
Automatic transfer switches come in a variety of amps, ranging from 50-amps to 400-amps.
In most cases, you simply match the transfer switch to the main breaker in your electrical panel, (it's usually located at the very top of the box.) So, if you have a 200-amp main breaker, you'll need a 200-amp automatic transfer switch.
Automatic Transfer Switches come in one of three styles: Standard, Load Centers, and Service Disconnects.
Rarely installed today, these sub-panel types have to be completely wired for each circuit, making them an expensive option to install.
Instead of installing an automatic transfer switch AND a sub-panel, a load center combines them into a single unit.
Load centers are ideal for standby generators powering small homes with 50 to 100-amp inbound service. Your electrician simply connects the load center to 8-16 mission critical circuits.
Unless you own a tiny home, you’ll still experience a mini-blackout with a load center. When a high-demand appliance – like a central air conditioner – turns on, the extra electricity generated cannot be diverted to other circuits.
The best option, by far is a service disconnect switch. Especially if you have an electrical service of 150 amps or higher, or if 16 circuits just aren’t enough. A service disconnect will energize your entire electrical panel.
Your electrician installs it between your meter and electrical panel. While their initial cost may be greater than a load center, you'll save a great deal on installation and you won't need to purchase a sub-panel.
In the past, home standby generators could not power several high-load appliances, like two central air conditioners, at once because the electrical demand was too great and caused an overload.
Nowadays, that is not a problem because you can get either a load center or a service disconnect that comes with A/C Shedding capabilities to manage higher load items. Let's look into each further.
Load Center + AC Shedding
New sophisticated load centers will always energize 16 essential circuits during an outage.
Two of the circuits could be connected to central air conditioners, allowing either to start but not simultaneously.
Service Disconnect + A/C Shedding
A better option is to use a service disconnect switch to power the entire panel and lock out a few high-demand appliances instead.
If the system doesn't have enough juice, the service disconnect will lock out up to four individual HVAC loads, preventing them from starting.
In addition to the built-in A/C shedding functionality, you can install Power Management or Smart Management Modules (PMM)(SMM) that will manage up to 8 additional loads to cycle, so you'll never have to worry about those higher-voltage appliances tripping the system.