Automatic Transfer Switches

Automatic Transfer Switches

Automatic Transfer Switches control Power. In normal operation, electricity flows from the utility lines to the home or business main circuit breaker panel. When a power outage hits, the generator starts and runs for a few seconds. When it is ready to take the load, it signals the Automatic Transfer Switch. The ATS disconnects the utility, then connects the generator to restore power. When the utility restores power, the transfer switch disconnects the generator, then connects the utility. The Generator Automatic Transfer Switch is an essential and necessary part of a standby generator system.

Generator Automatic Transfer Switch Rating

The Generator Automatic Transfer Switch must carry all the power from either the utility or the generator. The ATS rating in amps must meet or exceed the circuit breaker panel rating in amps. If the ATS connects to a 200-Amp panel, the minimum ATS rating is 200 amps.

Confusion arises when the ATS rating exceeds the panel rating. A 100-Amp Panel requires a Minimum ATS rating of 100 Amp, but a 200 Amp panel also meets code because it exceeds the circuit breaker panel rating. The 100-Amp circuit breaker in the panel would trip before the current exceeded ATS rating of 200 amps.

Automatic Transfer Switches for Generators

A Service Entrance Rating or Service Disconnect Rating allows Automatic Transfer Switches for Generators to operate as the main disconnect for the panel it feeds. A service disconnect is always required, either in the main panel as the main circuit breaker, or a separate service disconnect between the meter and the panel. The SE, SER, or SED rating allows the ATS to operate as a service disconnect.

An Automatic Transfer Switch with Power Management allows a smaller generator to handle power for heavy loads instead of a larger, more expensive generator. Priority-based management is the most common. Each heavy load has a priority and can run, in order of priority, when power is available. For example, air conditioner 2 runs when air conditioner 1 is not running.