@Nicholas Slater. Cheaper to get a 4CH PRO R3 as this comes with 4 relays that work with 24AC. The normal 4CH R3 only has 240v outputs and no relays.
@Hilton Ralphs Are you saying I can connect the solenoid valves directly to the 4CH PRO R3?
@Nicholas Slater. Correct. The output on the Pro version are just relays (switches) so you can just connect the live/red wire of your 24v AC solenoid power supply the first COM terminal and then bridged across to the other three COM terminals. From each NO terminal you run a live/red wire to each solenoid and from the 24v AC power supply you run a black/neutral wire to each solenoid valve. Timer just closes the NO terminal resulting in power from the 24v AC solenoid power supply reaching the valves. You need to run AC to the 4Ch Pro though but this has nothing to do with the relays.
@Hilton Ralphs Awesome man I had not thought of doing it like this. I found a post about this after you had mentioned it
I have both a step down converter (240V to 24V) that can be used as the input to the Sonoff, and a 4CH Pro R3 so I'll give this a go for my 3 solenoid valves and post back.
Thanks again :)