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Safety Analysis — SELV Spa-Light Switch Controller

Status

Draft design-stage safety analysis.

Applicable Standards to Review

AS/NZS 3100
AS/NZS 3820
AS/NZS 3000
AS/NZS 60529 / IP67
AS/NZS 60669 where applicable
AS/NZS 60335.2.60 if classified as spa/whirlpool equipment
IEC/EN 60335-1 and IEC/EN 62368-1 evidence for the isolated PSU module

Hazard Summary

Table

Hazard	Source	Mitigation in Schematic	Open Item
Electric shock	240 VAC input	Certified isolated RACM06E-12SK/277 PSU baseline, SELV-only controls, visible PCB isolation corridor	Layout creepage/clearance and safety engineer review required
Surge/transient	AC mains	Fuse F1 and MOV1	Confirm fuse type/rating and MOV coordination
False programming	Ambient/pool lighting	40 kHz IR receiver, firmware preamble/timeout requirement	Firmware validation through sealed optical port
Overtemperature	Sealed IP67 enclosure	NTC divider TEMP_SENSE	Define trip threshold after thermal testing
Unsafe relay state	Reset/brownout/invalid command	Firmware default relay OFF, single RELAY_DRIVE GPIO controlling Omron G2RL-2A-DC12 relay coil	Firmware implementation and watchdog tests
Power interruption	Mains loss	MAINS_PRESENT opto and supercap hold-up	Verify hold-up with measured current

Isolation Boundary

Primary-side / mains-switching nets: MAINS_L_IN, MAINS_L_FUSED, MAINS_N, LOAD_L_OUT, LOAD_N_OUT, PE_CHASSIS, MAINS_SENSE_LIMIT, MAINS_SENSE_IN. SELV-side nets: +12V_RELAY, +5V_ISO, +5V_HOLD, +3V3_MCU, 0V_ISO, RELAY_DRIVE, and all user I/O. The FODM214 optocoupler, RACM06E-12SK/277 PSU, and relay coil/contact isolation inside K1 cross or bridge the isolation boundary and must be verified against datasheets and layout geometry.

PCB Isolation / Creepage Placement Notes

PCB placement now includes visible top-side zone markings: MAINS / SWITCHED 240 VAC zone, 8 mm isolation / no-copper corridor, and SELV control zone.
Mains input/protection/relay/output components were placed on the left side; MCU, optical receiver, sensors, buttons, LEDs, programming connector, and low-voltage regulators were placed on the right SELV side.
Final routing must enforce no SELV copper, fills, stitching vias, or plane copper inside the isolation corridor except through certified isolation components.
Verify actual creepage/clearance on final routed layout around PS2, U4, K1 coil/contact separation, J1, J6, F1, MOV1, and mains sense resistors.
Current placement is not a safety approval; qualified safety engineering review is still required before energizing or manufacturing.

Required Before Mains Energization

Qualified electrical safety review.
Accredited lab compliance plan for Australian sale/use.
PCB layout creepage/clearance review, including confirmation that inner ground/power planes are split/kept out across the isolation corridor.
Enclosure/IP67 optical port validation.
Confirm relay/contactor stage is 2-pole mains-rated and reviewed separately.

Status
Applicable Standards to Review
Hazard Summary
Isolation Boundary
PCB Isolation / Creepage Placement Notes
Required Before Mains Energization