Motor Controllers

Troubleshooting

Common issues and solutions for the Starter 3-Phase (SP-3P) complete three-phase smart motor starter.

Section: Starter 3-Phase

Motor Does Not Start

Cause: SP-3P contactor not energising, overload relay tripped, or missing three-phase supply.

Confirm the SP-3P MX-3P LED is lit (green or blue). If dark, check 12V DC control power supply.
Confirm Online status in the app before issuing a start command.
On start command, the contactor should click. If no click: check the MX-3P LED changes state during the start — if not, the RS485 command is not reaching the module. Check gateway RS485.
Check for an overload relay trip — the reset button on the overload relay section of the SP-3P may be raised. Press firmly to reset, wait 60 seconds for the relay to cool, then retry.
Confirm three-phase mains supply: measure R-S, S-T, and R-T voltages at the SP-3P input terminals — all should read approximately 415V. Missing phase = motor cannot start.

Cause: Phase sequence at motor terminals is reversed — correct at motor terminal box, not at supply.

Isolate mains supply at the main switch-disconnector. Prove dead before opening the motor terminal box.
At the motor terminal box, swap any two of the three motor leads (e.g., swap U and V, or V and W).
Do NOT swap phases at the SP-3P supply input R/S/T — this reverses the sequence for all equipment on the supply.
Restore mains, restart from app, and confirm correct rotation before fitting the motor terminal box cover.
For submersible pumps: correct rotation is confirmed by comparing pump output flow — pumping water confirms correct rotation; minimal flow or heating indicates wrong rotation.

Cause: One or more supply phases absent, phase sense wires disconnected, or phase imbalance above threshold.

Measure R-S, S-T, and R-T voltages at the SP-3P input — confirm all three phase-to-phase voltages are approximately 415V.
Check the MX-3P phase sense wires at the SP-3P assembly — R, S, T sense terminals must be connected. Loose or disconnected sense wires cause false phase-loss alarms.
If all phases present at supply but one phase sense reads 0V in the app: check continuity of that sense wire from the SP-3P input bus bar to the MX-3P sense terminal.
Intermittent phase-loss alarms: check for loose supply connections at the supply incomer, or at the SP-3P R/S/T input terminals.
Reset the fault latch at Device → Reset Fault in the app after confirming all phases are stable.

Cause: Overload relay FLA dial set too low, motor drawing excess current, or unbalanced loading.

Confirm the FLA dial on the SP-3P overload relay is set to the motor nameplate FLA — not the MCB rating.
Measure motor running current on all three phases with a clamp meter — identify which phase is highest.
If all three phases are within nameplate FLA but the relay still trips: check the overload relay class setting (Class 10 for standard motors, Class 20 for high-inertia loads).
If one phase current is significantly higher than the others (>10% imbalance): investigate for voltage imbalance at the supply, a failed motor winding, or mechanical binding.
For motors with repeated unexplained trips at correct FLA setting: fit a current event logger to capture the current profile at the moment of trip — the motor may be experiencing locked-rotor or blocked-rotor events.

Cause: Gateway internet connection lost, RS485 cable fault, or 12V DC power failure.

Check gateway Online status — if the gateway is offline, all its devices show offline. Restore gateway internet first.
If only the SP-3P shows offline: check RS485 terminals at the SP-3P assembly and at the gateway.
Confirm MX-3P LED is lit on the SP-3P assembly. If dark: check 12V DC power supply.
Power-cycle the 12V DC control supply to the SP-3P — module reconnects within 60 seconds.
Tug RS485 terminal wires lightly at both ends — a loose screw terminal is the most common RS485 fault.

LED Pattern	Status	Action
Solid Green	Running normally, three phases present	Normal — no action needed
Flashing Blue	Pairing mode — waiting for RS485 scan	Perform RS485 scan from gateway settings
Solid Amber	Overload relay tripped or coil circuit fault	Reset overload relay; investigate load; reset fault in app
Solid Red	Phase-loss detected	Check three-phase supply; reconnect sense wires if loose; reset in app
Flashing Amber	Dry-run stop active	Check water source level; reset dry-run latch in app when level restored
No LED	No 12V DC control power	Check 12V DC supply and connection to MX-3P module inside SP-3P assembly