I am setting up a relay to control my 120v/15a pool light. The relay control will be located in a plastic project box near the pool equipment and will be driven by a 24VAC coil. The light circuit will be a dedicated breaker in the nearby sub-panel. (I'm using 24VAC as it is already available in the project box to drive pool valve actuators).
I would like the relay to tie into a normal 3-way switch mounted outside which would serve as a "manual override" in the event someone needs to turn the light on or off and doesn't have access to the automation control that drives the relay.
Normally, I would wire this by running THWN hot/neutral/ground through conduit from the sub-panel to the project box relay, connect the relay NO/NC contacts to two travelers and run those two plus the neutral/ground wires through conduit to the manual switch, then on to the light itself. However, I'd like to reuse an existing switch already mounted adjacent to the sub-panel (it's not a 3-way, but I will replace it with one).
As a simpler alternative, can I safely to run a single THWN hot wire from the sub-panel breaker through conduit to the project box into the relay's common contact, and two THWN wires (travelers) from the relay's NO/NC contacts back through the same conduit (3 wires total) into the sub-panel. From there, the two travelers, a neutral, and a ground in a separate conduit connecting to a physical 3-way switch, then the 3-way switch's single pole, neutral, and ground make their way to the pool light fixture. Is this code-compliant or safe?
This feels very strange (wrong) to me and now that I've written out the question I'm fairly confident it isn't compliant and I should go with my first approach.