{"product_id":"st420f-series-combined-electrical-fire-monitoring-detector-3-in-1-protection-monitoring","title":"ST420F Series Combined Electrical Fire Monitoring Detector | 3-in-1 Protection \u0026 Monitoring","description":"\u003cp\u003eThe ST420F integrates a low-voltage microprocessor-based line protection relay, multifunction power meter, and residual current electrical fire monitoring detector into a single intelligent device. It provides comprehensive low-voltage circuit protection, measurement, management, and communication functions — while simultaneously monitoring residual current for electrical fire hazards and triggering alarms before fire incidents occur.\u003c\/p\u003e\u003cp\u003eThe ST420F has passed dual certification testing and is widely applicable in industrial, commercial, and civil power systems as well as substations.\u003c\/p\u003e\u003ch2\u003eKey Features\u003c\/h2\u003e\u003ch3\u003eElectrical Fire Monitoring\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eMonitors 1-channel residual current (20–1000mA)\u003c\/li\u003e\n\u003cli\u003eAudible and visual fire alarm with graphical color display\u003c\/li\u003e\n\u003cli\u003eFire linkage: 2-channel relay output\u003c\/li\u003e\n\u003cli\u003e2-channel digital input (DI)\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eComprehensive Low-Voltage Line Protection\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eInverse-time overcurrent protection\u003c\/li\u003e\n\u003cli\u003eDefinite-time overcurrent protection\u003c\/li\u003e\n\u003cli\u003eZero-sequence overcurrent protection\u003c\/li\u003e\n\u003cli\u003eInverse-time zero-sequence overcurrent protection\u003c\/li\u003e\n\u003cli\u003eInstantaneous overcurrent (fast trip) protection\u003c\/li\u003e\n\u003cli\u003eResidual current protection\u003c\/li\u003e\n\u003cli\u003ePhase-loss protection\u003c\/li\u003e\n\u003cli\u003eUndervoltage \/ overvoltage protection\u003c\/li\u003e\n\u003cli\u003eCurrent unbalance protection\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eMultifunction Metering (Accuracy Class 0.5)\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eThree-phase current \u0026amp; voltage\u003c\/li\u003e\n\u003cli\u003eActive \/ reactive power\u003c\/li\u003e\n\u003cli\u003eActive \/ reactive energy (kWh)\u003c\/li\u003e\n\u003cli\u003ePower factor \u0026amp; frequency\u003c\/li\u003e\n\u003cli\u003ePositive \/ negative sequence current \u0026amp; voltage\u003c\/li\u003e\n\u003cli\u003eThree-phase current \u0026amp; voltage unbalance\u003c\/li\u003e\n\u003cli\u003e1st–7th harmonic current \u0026amp; voltage\u003c\/li\u003e\n\u003cli\u003eResidual current\u003c\/li\u003e\n\u003cli\u003eAverage current\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eIntegrated Solution Advantages\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eEliminates redundant investment in separate fire monitoring detectors and residual current transformers\u003c\/li\u003e\n\u003cli\u003eOptimized design — simplified installation, reduced failure points\u003c\/li\u003e\n\u003cli\u003eUnified HMI for easy operation\u003c\/li\u003e\n\u003cli\u003eOptimized communication channels, reduced infrastructure cost\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eCommunication \u0026amp; Networking\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eTwo independent RS485 interfaces (Modbus protocol)\u003c\/li\u003e\n\u003cli\u003eRS485 Port 1: connects to power monitoring master station or communication manager\u003c\/li\u003e\n\u003cli\u003eRS485 Port 2: connects to electrical fire monitoring system network\u003c\/li\u003e\n\u003cli\u003eBoth systems operate independently — meets fire inspection requirements\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eEvent Records\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e16 fault records\u003c\/li\u003e\n\u003cli\u003e8 digital input change records\u003c\/li\u003e\n\u003cli\u003e8 trip records\u003c\/li\u003e\n\u003cli\u003e8 protection reset records\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eI\/O Specifications\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eThree-phase current input: 1A \/ 5A\u003c\/li\u003e\n\u003cli\u003eThree-phase voltage input: AC 380V\u003c\/li\u003e\n\u003cli\u003eDigital input (DI): 2 channels, built-in DC 24V power supply\u003c\/li\u003e\n\u003cli\u003eRelay output (DO): 2 channels — Channel 1: AC 220V, resistive 5A; Channel 2: AC 220V, resistive 8A\u003c\/li\u003e\n\u003cli\u003eResidual current input: 1 channel, 20–1000mA\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eStandards \u0026amp; Certifications\u003c\/h2\u003e\u003cp\u003eDual certification tested. Suitable for industrial, commercial, and civil power distribution systems and substations.\u003c\/p\u003e","brand":"Wanlong Electric","offers":[{"title":"Default Title","offer_id":44140629917762,"sku":null,"price":350.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0688\/1221\/0242\/files\/ST420F_-3.webp?v=1784268465","url":"https:\/\/wanlongelectric.com\/products\/st420f-series-combined-electrical-fire-monitoring-detector-3-in-1-protection-monitoring","provider":"Wan Long Electric Group Co., Ltd.","version":"1.0","type":"link"}