| Manual changeover switches | Allow an operator to select between power sources by hand. | Operating handle, source-position indication, mechanical interlocking, and rated operational current. | IEC 60947-3 may apply to switch-disconnector designs; confirm the product’s declared compliance. |
| Automatic transfer switches | Monitor supply conditions and transfer a load between sources automatically. | Controller functions, sensing settings, transfer sequence, and documented operating limits. | IEC 60947-6-1 or UL 1008, where applicable to the equipment and target market. |
| Open-transition equipment | Disconnects one source before connecting the other, creating a break in supply during transfer. | Transfer interruption, interlocking, and suitability for loads that can tolerate a brief outage. | Check the applicable transfer-switch standard and the manufacturer’s declared transition mode. |
| Closed-transition equipment | Can briefly connect sources in parallel during transfer when the system and equipment are designed for it. | Synchronization requirements, permitted paralleling time, protection, and utility approval where required. | Verify applicable transfer-switch requirements and local interconnection rules. |
| Two-pole configurations | Switch two conductors; commonly considered in some single-phase arrangements. | System earthing arrangement, neutral switching requirements, and local electrical codes. | Confirm the applicable product standard and installation rules for the specific system. |
| Three-pole configurations | Switch three phase conductors in compatible three-phase systems. | System voltage, current rating, fault withstand capability, and neutral arrangement. | Check the declared standard, ratings, and test documentation for the complete assembly. |
| Four-pole configurations | Switch three phases and the neutral where the system design calls for it. | Neutral pole design, switching sequence, and compatibility with the installation’s earthing scheme. | Verify the applicable product standard and system-specific installation requirements. |
| Motor-operated switches | Use an electric motor mechanism for remote or automatic operation. | Control-supply requirements, manual operation provision, position feedback, and interlocks. | Confirm that the complete transfer-switch assembly—not only its mechanism—is appropriately certified. |
| Bypass-isolation transfer equipment | Provides a means to isolate transfer equipment for inspection or maintenance while maintaining a supply path where the design permits. | Bypass operating sequence, isolation provisions, interlocking, and maintenance procedures. | Review the applicable transfer-switch standard and the certified assembly documentation. |
| Enclosed changeover assemblies | Combine switching equipment with an enclosure for installation as an assembly. | Enclosure protection rating, ambient conditions, cable entry, temperature rise, and installation clearances. | Check both the switching-device requirements and any applicable enclosure or assembly requirements. |