Most smart (WiFi remote) light switches available online say "neutral wire required". For example, this Gosund dimmer. In some older houses, this requirement for a neutral in the switch box is problematic. (I understand the NEC has been updated to require a neutral in switch boxes for new construction. Cool.)
Reading online, I found this NEC quote:
2017 Code Language:
N 404.22 Electronic Lighting Control Switches.
Electronic lighting control switches shall be listed. Electronic lighting control switches shall not introduce current on the equipment grounding conductor during normal operation. The requirement to not introduce current on the equipment grounding conductor shall take effect on January 1, 2020.
Exception: Electronic lighting control switches that introduce current on the equipment grounding conductor shall be permitted for applications covered by 404.2(C), Exception. Electronic lighting control switches that introduce current on the equipment grounding conductor shall be listed and marked for use in replacement or retrofit applications only.
My understanding of the exception above is that allows for replacement or retrofit smart switches which use a ground rather than neutral to power the electronics. Have I got that right?
Are such retrofit devices available? Listed?
P.S. I understand the listing requirement to be satisfied by an ETL listing, such as the Gosund seems to have.