Thanks for your response Ray. The ERV control is factory set to constant on… In order to enable external control, they have you remove a wire nut that connects a relay to a transformer… then you connect those two wires to your external controller… I would connect one wire to the OpenSprinkle common and the other to the OpenSprinkler Station 1… The ERV controller transformer is 24V AC, 420 milliamps, so I am thinking this will work.
Thanks again.