I'm trying to upgrade to a new line voltage thermostat. The new thermostat has many more connections, including three fan speeds. My current system has a manual fan switch on the wall so all I need the thermostat to do is allow power to flow to the fan coil unit.
This diagram tries to show how the system is wired and a proposed new wiring. I propose this because I've tried attaching the heat and cool and neutral from the new thermostat to the R, and the black to the black. The white wire is capped at the thermostat and junction box ends, but I'm proposing to use that as the neutral connection at the thermostat and add it to the W to W current connection in the junction box. Any advice on whether this would work?