Repeated 'master valve' zone faults in controller with Sprecher + Schuh CA7/16 contactor after initial success—current draw issue or something else?

I’m looking for guidance regarding my current wiring setup.

The controller is connected with a Sprecher + Schuh CA7/16 contactor, 24VAC coil, on the master valve contacts, with the controller set to ‘well or pump start relay’ in the app. The contactor runs a bore pump.

When running an irrigation cycle, everything runs fine the first time (pump turns on, phase solenoids actuate correctly, no warnings or errors - all through multiple zones, over a short or long periods). When running the next cycle, the controller reports a zone fault on the ‘master valve’. The fault clears when stopping the cycle, but occurs persistently until the controller is power cycled again. Once power cycled, the controller can again run normally (once) before the issue repeats.

The 24VAC contactor coil has a hold-in consumption of 9.5 VA (~0.4A), but a pick-up consumption of 75 VA (~3.1A). I know the controller has a 1.3 A consumption limit, but would expect if this was the issue it wouldn’t work at all - not work once, then fault until power cycled, then work again (once).

Power frequency is 50Hz, being in Australia.

Hoping the community can provide some guidance on whether this is simply an issue with the installed contactor current draw, or if there’s something else going on.

Contactor datasheet:

@mdroberts88 - I’m thinking is is the inrush on the pick-up. A way to potentially work around this is to have a small SPST NO (single pole, single throw, normally open) relay switch that the Rachio would connect to and have a bigger 24 VAC power supply routed through the new relay switch to the Sprecher + Schuh contactor.

Hi @DLane - Thanks very much for your support. The issue was indeed the inrush current and a small solid state SPST NO relay switching 24VAC from the main transformer (bypassing the controller) resolved the issue. I’m still unclear as to why the controller accepted the higher inrush current without faulting the first time, and then faulted the second time (and all subsequent attempts thereafter), but as it’s working now I will happily let it go.

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