Transfer equipment
Transfer equipment selects which source supplies a building or a group of circuits. In a generator system, it is the connection between utility power, generator power, and the loads being backed up.
In this topic
Manual and automatic operation
A manual transfer system requires an operator to initiate the change of source. An automatic transfer switch monitors power sources and transfers eligible loads when its operating conditions are met. Automatic operation also requires compatible generator controls; a transfer switch alone does not make every generator automatic. [1]
The operating method is separate from the transition method. An open transition disconnects one source before connecting the other. Some engineered systems use other arrangements, including closed transition, that require additional coordination. [1]
Read the system, not just the amp rating
Transfer-switch specifications include voltage, frequency, current rating, enclosure suitability, fault-current ratings, and application details. A qualified electrical designer or installer must also consider the neutral and grounding arrangement and where the equipment sits in the service. [1]
Never connect a generator to house wiring through a wall outlet. This dangerous practice, called backfeeding, can energize utility lines and expose workers and neighbors to electrocution. A building connection needs suitable transfer equipment installed for that particular system. [2]
Sources and further reading
- Eaton: transfer operation, transitions, and system selection ↗www.eaton.com
- CPSC: electrical hazards and backfeeding ↗www.cpsc.gov
Use the manual and nameplate for the exact model. Local requirements and site conditions take precedence over general examples.