Some photovoltaic (PV) inverter manufacturers have designed and built transformer-less inverters to add to their existing line of transformer-type inverters for installation in the United States. Transformer-less inverters have been popular in Europe for quite some time.
Article 450 in the National Electrical Code (NEC) covers requirements for transformers. The scope of Article 450, located in 450.1, states that it covers the installation of all transformers, but there are eight exceptions.
If you have a problem related to the National Electrical Code (NEC), are experiencing difficulty in understanding a Code requirement, or are wondering why or if such a requirement exists, ask Charlie, and he will let the Code decide. Questions can be sent to firstname.lastname@example.org.