Three-phase pumps scare buyers away from remote control, usually unnecessarily. The switching logic is identical to single-phase — the only questions are how many poles the switch must carry and whether the 4G unit switches the load directly or drives a contactor coil. This guide covers both routes with the wiring in plain language.
Route 1: direct switching up to the switch rating
The AT-SY7 three-phase 4G switch is a true three-pole switching device: all three phases are broken and made together, never sequentially, and the unit handles loads to its rated current. For a 4–11 kW three-phase pump (roughly 9–21 A at 380 V), direct switching is the cleanest installation: the 4G switch sits between the upstream protection and the pump, three phases in, three phases out, control circuit powered from the same supply.
Wiring in five steps: (1) isolate and lock off the supply; (2) land the three phase conductors and, if the pump requires it, the neutral on the input side; (3) land the pump conductors on the output side, keeping phase rotation consistent with the pump's marked rotation — if the pump runs backwards, swap two output phases; (4) connect the earthing directly to the pump frame, never through the switch; (5) restore power, pair the unit in the app and run one manual start to confirm rotation and current.
Route 2: contactor drive for larger loads
Above the switch rating — or for motors with heavy starting currents — the 4G switch moves into the control circuit. The AT-SY5 63 A single-phase 4G switch or the AT-SY7 feeds the contactor coil instead of the motor. The contactor does the heavy lifting; the 4G switch does the thinking. Choose an AC-3 rated contactor for motor duty, sized at least 1.2× the motor's full-load current, and put the coil circuit on a small fuse or MCB.
This architecture also solves the star-delta and soft-starter cases: the 4G switch enables the starter's control line, and the starter keeps its own sequence wiring untouched. Every switching event is logged in the app, which is what irrigation districts and pump-station operators use as an operating record.
Protection stays upstream
A remote switch — any remote switch — is not overcurrent protection. The pump's short-circuit and overload protection (breaker + overload relay or a motor protection breaker) sits upstream and remains mandatory. What the remote unit adds is visibility: because the app shows live status, an upstream trip shows up immediately as "commanded ON, zero current" instead of being discovered at the next site visit.
Common mistakes
- Switching only two phases to "save" a pole — the third phase stays live at the pump terminals, which is dangerous during maintenance. Read true 4P vs 3P+N for why pole-by-pole switching matters.
- Undersized contactor for the motor's starting current — the contacts weld after a season of starts. Use AC-3 ratings, not AC-1.
- No dry-run protection on an unattended pump — add a schedule with minimum off-time, or a float/pressure interlock in the control circuit.
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