Choosing a refrigerant sensor for A2L HVAC equipment is not only a gas-detection decision. It is a system decision tied to refrigerant type, alarm threshold, controller logic, installation position, and long-term reliability. Under UL 60335-2-40, refrigerant detection system requirements were refined to improve robustness, reliability, and lifetime drift evaluation, and the system response is tied to refrigerant concentration at 25% of the lower flammability limit (LFL).
At Winsen, we recommend starting from the application architecture, not from a single product model. Our refrigerant sensor solutions cover A1 and A2L refrigerants, including R32 Ve R454B, with NDIR, thermal-conduction, and semiconductor options that support functions such as leak alarm and automatic switch-off.
1. Start with the refrigerant and the safety target
The first question is simple: what exactly are you trying to detect, and at what response level? For A2L HVAC equipment, that usually means refrigerants such as R32 veya R454B, and the selection has to align with the equipment’s refrigerant detection strategy. TI’s 2024 A2L guidance states that the refrigerant detection system should make output within 30 seconds of direct exposure to 25% LFL, while UL explains that the system must initiate response when it senses % LFL and that the integral RDS, when required, is evaluated as part of the HVAC equipment certification.
In practical engineering terms, this means you should first decide whether you need:
- a module for A2L RDS logic in heat pumps or air handlers,
- a compact embedded sensor for a board-level design,
- or a ppm-level alarm solution for a different control concept.
Those are not the same selection path.
2. Choose the sensing principle that fits the equipment
For A2L HVAC equipment, the most common Winsen solution path is N. On our refrigerant sensor solution page, we position semiconductor and NDIR infrared refrigerant sensors for qualitative and quantitative detection of A1 and A2L refrigerants, and our product pages for the ZRT512E- ZRT510, Ve MH-Z1542B all describe NDIR detection with good selectivity and no oxygen dependence.
For heat pump OEMs, NDIR is usually the right direction when you need:
- stronger selectivity,
- stable long-term output,
- and integration into A2L refrigerant detection logic.
For example, our ZRT512E-R454B & R32 module targets R454B and R32, supports 0–100 LFL, uses Rs485, and is specified with high sensitivity, high resolution, fast response- built-in temperature compensation- anti-water-vapor interference, Ve uzun servis ömrü.
If your design priority is small size, low power, and anti-condensation performance, A thermal-conduction module can be the better choice. Our ZR210 targets R32 and R454B, uses a thermal-conduction principle, and is described with fast response- küçük boy- düşük güç tüketimi- long life, Ve good anti-condensation effect; the listed size is 37 × 20 × 7 mm with Uart output.
If you need a compact embedded R32 sensor for a board-level design, our MH-Z1542B-R32 is another practical option. It is an N sensor with UART output- 0–5.00% vol measurement, 0–50% LFL range for R32, T25 < 7 s- anti-water-vapor interference, Ve lifespan >15 years.
If your project is closer to a ppm-level alarm design than a full A2L RDS module, our ZP201 Ve MP511D are relevant. ZP201 is a factory-calibrated refrigerant gas detection module for air-conditioning and refrigeration leak detection with high sensitivity- fast response- strong anti-interference, Ve sensor fault self-diagnosis. MP511D is a semiconductor Freon gas sensor built on a metal-oxide semiconductor layer for refrigerant detection in ambient air.
3. Match the module to your controller architecture
Once the sensing principle is chosen, the next selection factor is how the sensor will connect to the control system. UL’s guidance emphasizes that RDS wiring must be correctly connected to the RDS controller and to equipment controls so mitigation actions can be initiated correctly.
That is why interface choice matters early. In our current portfolio:
- ZRT512E-R454B & R32 uses Rs485 and updates data every 1 saniye.
- ZRT510-R454B supports RS485/UART, with PWM customizable.
- MH-Z1542B-R32 provides Uart output.
- ZR210 is presented with Uart output.
In practice, we recommend:
- Rs485 when the product needs stable digital communication over the appliance control architecture,
- Uart when the sensor is more directly embedded on a local board,
- and simpler ppm-level module outputs when the application is closer to a focused leak alarm design than a full A2L HVAC RDS.
4. Select the package for the real installation space
For A2L HVAC equipment, package size is not a cosmetic issue. UL states that A2L refrigerants are heavier than air, so installation instructions will typically place sensors where leaked refrigerant is likely to sink and collect, most often near the indoor coils toward the bottom of the enclosure. Units with multiple indoor coils will typically use multiple sensors, and orientation can change the correct sensor location.
That means the sensor module should be selected with the installation point already in mind:
- If you need a larger integrated module with broader A2L performance and digital communication, ZRT512E is a strong fit.
- If you need a compact enclosure-friendly module- ZR210 is easier to place in tight spaces.
- If you need a compact embedded NDIR core for a custom board or housing, MH-Z1542B-R32 fits that approach.
- If you want a dedicated refrigerant-specific module, ZRT510 family gives a direct path.
5. Check response, lifespan, and environmental robustness
For A2L HVAC equipment, a fast reading is not enough. UL’s current framework also emphasizes deviation and drift over the lifetime of the refrigerant sensor, and requires evidence to substantiate claimed sensor life.
That is why we recommend checking at least these five items during selection:
- response time,
- preheat time,
- working temperature and humidity,
- long-term lifespan,
- and anti-interference or anti-condensation behavior.
Örneğin:
- ZRT512E-R454B & R32 is specified with response time ≤15 s- anti-water-vapor interference, Ve uzun servis ömrü.
- ZRT510-R454B is specified with response time <15 s- -40 to 85 °C- 0–100% RH, Ve life span >15 years.
- MH-Z1542B-R32 is specified with T25 <7 s- 0–95% RH (no condensation), Ve lifespan >15 years.
- ZR210 is described with uzun servis ömrü Ve good anti-condensation effect.
6. Choose by application scenario, not by product popularity
For most OEM projects, the right choice becomes clearer when you map the module to the real system role.
If the project is a mainstream A2L heat pump or HVAC platform needing strong selectivity and controller communication, we usually recommend starting with ZRT512E-R454B & R32. It covers R32 and R454B, supports 0–100 LFL, and is designed for HVAC, refrigeration systems, and heat pumps.
If the project is a space-constrained indoor unit or a design sensitive to power and condensation, ZR210 is usually the better starting point because of its küçük boy- düşük güç tüketimi, Ve anti-condensation profile.
If the project needs a refrigerant-specific NDIR module with broader interface flexibility, the ZRT510 family is a strong option. The R454B version is specified at 0–50% LFL- RS485/UART, customizable PWM, Ve >15 years lifespan.
If the project needs a compact board-level R32 sensor- MH-Z1542B-R32 is a very practical solution with Uart- fast response, Ve small footprint.
If the project needs a ppm-level leak alarm module rather than a full A2L RDS-oriented module, ZP201 veya MP511D may be the more appropriate path.
7. Do not separate sensor selection from mitigation logic
UL defines an integral RDS as a system using one or more stationary sensors to detect a refrigerant leak at a specified concentration and automatically initiate mitigating actions. UL also notes that typical mitigation actions include turning on the indoor fan, opening dampers, turning off the compressor unless pump-down is required, closing shut-off valves, and initiating alarms or mechanical ventilation. TI’s A2L mitigation note describes the same broader architecture: sensor module, mitigation board, and control actions.
So, when choosing the refrigerant sensor, we recommend asking one final question:
Is this sensor only detecting gas, or is it part of the final system response strategy?
For A2L HVAC equipment, that distinction usually determines whether you should choose an embedded ppm sensor, a compact UART NDIR sensor, or a full module designed for RDS-oriented system integration.
Çözüm
At Winsen, we recommend selecting an A2L refrigerant sensor in this order:
refrigerant first, threshold second, sensing principle third, interface fourth, package fifth, and lifetime reliability throughout. That approach is more reliable than choosing purely by price or package shape.
For most A2L HVAC equipment:
- choose N when you need selectivity, stable output, and RDS-oriented integration,
- choose thermal conduction when size and anti-condensation are the main engineering priorities,
- and choose semiconductor ppm solutions when the project is a more focused leak-alarm design rather than a full A2L HVAC RDS implementation.
