Types of Transfer Switches

Transfer switches are essential to backup generators.

Transfer switches are designed to supply power to electrical circuits from multiple power sources. They prevent the risks of electrocution and are required for any backup generator. There are three types of transfer switches: manual, automatic and combination.

Manual

Manual transfer switches (MTS) are the least expensive and least complicated. They require someone start and stop the generator as well physically operate the MTS. This transfer switch comes in a variety of sizes and configurations. Manual transfer switches are used by portable and stationary generators.

Automatic

Automatic transfer switches are best in times over power outages It is capable of monitoring the power supplies and automatically switching from utility supply to the generator power source. When power is restored, it automatically shuts the generator down and transfers back to the normal power source. Maintenance schedules can be predetermined to ensure the backup generator works when needed. It has various control and alarm features.

Combination

Combination transfer switches function as either an automatic transfer switch or a manual transfer switch, depending mode of operation. This allows for flexibility in use.

References

• Prime Power: Emergency Power Supply Systems Experts
• Bowers Generator Systems:Transfer Switches
• CPSC: U.S. Consumer Product Safety Commission
• Sommers: Automatic Transfer Switches
• Cummins Power: Application Engineering -- Transfer Switch Application Manual