I recently installed a DC controller, replacing an older PC controlled unit. All the relays and valves are designed for 24v AC.
It is now working just fine and currently runs three valves and a pump relay concurrently with no problem.
It seems inevitable, however, that at some time in the future, we will suffer from a drought once again, and will have to live with restrictions on our watering days. When that happens, I will probably want to increase the concurrent operation by at least one more valve. I have not found any information about what the maximum number of concurrently operating solenoids is. I am supposing that if the hardware and the software are not stressed, the power supply might be.
Do you have any information on this topic?