Cubic AM4203H NDIR Refrigerant Gas Sensor

Overview

The Cubic AM4203H is a purpose-engineered non-dispersive infrared (NDIR) refrigerant gas sensor designed for continuous, reliable detection of flammable A2L and A3 refrigerants—including R32, R454A, R454B, R454C, and R290—in HVAC&R equipment. Unlike electrochemical or catalytic bead sensors, the AM4203H leverages dual-wavelength NDIR optics with temperature-compensated signal processing to deliver stable, drift-resistant measurements across wide ambient conditions. Its core architecture eliminates reliance on field calibration by incorporating an advanced automatic baseline correction algorithm that dynamically adjusts for optical aging and environmental drift—enabling true maintenance-free operation over its rated 15-year service life. The sensor is explicitly validated for integration into fan coil units, gas-fired furnaces, and heat pump systems where early leak detection, system-level mitigation, and compliance with North American safety standards are critical.

Key Features

• True NDIR optical sensing platform optimized for hydrocarbon and mildly flammable refrigerants (R290, R32, R454x series)
• Integrated dry-contact relay output enabling direct control of fans, compressors, or shutdown circuits without external controllers
• Robust mechanical and environmental resilience: IP54-rated enclosure; operational stability from −30 °C to +70 °C and 0–95% RH (non-condensing)
• Dual power input compatibility: supports both AC (18–36 V, 55±8 Hz) and DC (12–36 V) supplies—ideal for retrofit and OEM applications
• Modbus RTU protocol over RS485 for seamless integration into BMS, PLC, or SCADA architectures with configurable slave ID and baud rate
• UL 60335-2-40 and UL 60335-2-89 certified—validated for use in household and similar appliances containing flammable refrigerants

Sample Compatibility & Compliance

The AM4203H is calibrated and verified for quantitative detection of five key next-generation refrigerants: R32 (difluoromethane), R454A/B/C (zeotropic blends with low GWP), and R290 (propane). All measurements are referenced to Lower Flammability Limit (LFL) concentration thresholds per ASTM E681 and ISO 10156. The sensor meets the stringent requirements of UL 60335-2-40 (Refrigerating Appliances) and UL 60335-2-89 (Gas-Fired Heat Pumps), including fault diagnostics, self-monitoring, and fail-safe relay behavior under sensor degradation or power loss. It supports GLP/GMP-aligned deployment through deterministic response time (T90 ≤30 s), traceable accuracy specifications, and documented long-term stability—making it suitable for regulated environments requiring audit-ready performance records.

Software & Data Management

While the AM4203H operates as a standalone analog/digital sensor, its RS485 Modbus interface enables full parameter configuration and real-time telemetry via industry-standard protocols. Supported registers include live gas concentration (%LFL), sensor status flags (e.g., fault, warm-up, calibration lock), relay state, and internal temperature/humidity compensation values. When integrated into larger building management systems, data logging, alarm thresholding, and event-triggered mitigation sequences (e.g., fan ramp-up at 10% LFL, compressor shutdown at 25% LFL) can be implemented without proprietary software dependencies. No cloud connectivity or firmware updates are required—firmware resides in write-protected memory to ensure deterministic behavior under IEC 61508 SIL2-aligned operational profiles.

Applications

• Leak detection and automatic shutdown in residential/commercial heat pumps using A2L refrigerants
• Safety interlock for gas-fired HVAC systems compliant with ASHRAE 15–2022 and IMC Section 1103.1
• OEM integration into fan coil units requiring localized refrigerant monitoring and ventilation override
• Retrofit solutions for legacy chillers transitioning to low-GWP refrigerants under EPA SNAP program guidelines
• Continuous monitoring in refrigerant charging stations, recovery carts, and service bays per IIAR Bulletin #114

FAQ

Does the AM4203H require periodic field calibration?
No. It employs an embedded auto-baseline correction algorithm that compensates for optical drift and environmental aging—eliminating scheduled calibration throughout its 15-year design life.
Can the relay output be configured for normally open (NO) or normally closed (NC) operation?
Yes. The relay is programmable via Modbus register to operate in latching or non-latching mode with configurable activation thresholds and hysteresis.
Is the sensor compatible with BACnet MS/TP or KNX networks?
Not natively—but when paired with a standard Modbus-to-BACnet or Modbus-to-KNX gateway, full interoperability is achieved without custom drivers.
What is the expected lifetime under continuous operation at 60 °C and 85% RH?
Accelerated life testing confirms >15 years MTBF under those conditions, consistent with IEC 60721-3-3 Class 3K6/3Z2 environmental stress profiles.
Does Cubic provide third-party test reports for UL certification?
Yes—full UL certification documentation, including test reports from UL Solutions (File E491100), is available under NDA to qualified OEM and system integrator partners.