I'm mentioned Mike Sokol here before. He's a EE and RV writer and darn good at what he does.
This article answers so many questions about "How to wire an RV outlet"
This article answers so many questions about "How to wire an RV outlet"
How to Install a 30-Amp RV Outlet at Home…
Make sure your electrician understands that a 30-amp RV outlet is wired for single-pole 120 Volts!
rvelectricity.substack.com