What is a transfer switch and should I purchase a manual or automatic transfer switch (ATS)?

A transfer switch is a device that switches between utility and generator power. It isolates the two types of power. The National Electrical Code requires this type of devise for stationary generators to avoid back feeding power into the utility grid.

This can be accomplished with a manual transfer switch where the operator will physically transfer the power via a control system or breaker. When power resumes, the control system or breaker must be manually transferred back to the utility by the operator. There must be an operator available and the need for power should not be critical to the operation.

An automatic transfer switch (ATS) will monitor utility power and automatically switch to generator power should there be an interruption in utility power. Once utility power resumes, the ATS will automatically transfer power back to the utility and turn off the generator.

Note: there is a 7-10 second delay from the time the utility power is lost until the generator is on-line. If any loss of power is unacceptable, then an Uninterruptible Power Supply (UPS) will need to be installed between the generator and the equipment load. Contact your generator sales engineer for size and pricing.

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