How many sprinkler stations should be on at the same time?

[Sean]

What is the advised or practical limit to the number of valve solinoids that an OS system should activate at the same time?

[Ray]

The firmware does not limit the number of parallel stations — the limit depends on the current rating of your sprinkler transformer. Just to give you an idea: each solenoid, when open, draws about 180 to 250mA of current. So if your sprinkler transformer is 750mA, you can most likely run 4 valves at the same time — in practice it can be more, because as more valves are open, the total current draw increases, which drives down the output voltage of the transformer (AC transformers are un-regulated), thus the current per station reduces, and consequently more valves can open. I did some tests a while back, with a 750mA transformer I can open 8 valves at the same time.

[Author]

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