Check out this photo of one of our user’s installation. This user wanted to maintain its old controller side by side the new IrrigationCaddy. The wiring (even though the photo does not does it justice), is quite simple. Just wire the zones one to one. So a cable goes from a zone on the old controller, to a zone on the new controller (IrrigationCaddy).
Old-New-side-by-side
It is best if only one controller is triggering a zone at a time, but even if both are on at the same time the controllers should be ok.
I can confirm that this setup does in fact work well. I have an Orbit timer with a wireless transmitter that will activate any or all zones remotely. It’s excellent for tweaking heads without having to run back to the garage each time you want to start and stop a zone. While the irrigation caddy can accomplish the same thing using a mobile phone or tablet, neither is the kind of device you want to be handling with wet hands.
I would only stress that if you decide to use the same power supply to power both the existing system and the new timer, after verifying the current rating is enough of course, you must be careful it match the polarity of the systems. While they’re both AC, if the phasing is not correct you may burn up the power supply. When if first hooked up both, the power light on neither came on - and the wall wart was making a sound. I flipped the wires on one of the systems and everything works great now.
On a side note, I use my timer to ‘exercise’ my whole house diesel generator. It’s nice to be able to fire that up from anywhere now… even when traveling. Pretty cool stuff!
Has anyone tried scaling this to 16+ zones?