This is not X10 related but it is automation of sorts. I have a sprinkler system at my house that includes 11 zones. In the US, sprinklers run on 24VAC. I just replaced 2 ancient Rainbird brand timers with an Orbit B Hyve 12 zone smart timer. The old system was actually comprised of 3 timers (2 electeonic, 1 mechanical) and I'm keeping the most archaic for now since the manual timer was used on the garden.
The question is, if I wanted to have the garden sprinkler controller by both the mechanical and smart timer, can I simply wire them in parallel? If one is on and the other off I'm sure it would work. However, does feeding 24vac to the back side of either the mechanical or Orbits timer pose issues? Since its AC, I cant just install a diode so are there other ways?