A2L Gas Sensor Module
UL60335-2-40 Edition.3 requires refrigerant leak detection
for air conditioning equipment.

What is UL60335-2-40 Ed.3, which is about to be applied in North America?

UL60335-2-40 is an electrical safety standard for air conditioning and refrigeration equipment in North America, and Edition 3 adds a safety feature for A2L refrigerant.

In Edition 3, a safety function for A2L refrigerant will be added to the standard. Since A2L refrigerant is a mildly flammable refrigerant that is increasingly being introduced in response to greenhouse gas emission regulations, the incorporation of a refrigerant leak detection mechanism will be mandatory in Ed.3.
The security functions to be added in Ed.3 include alarm triggered by leak detection, shutoff by shutoff valve, and gas diffusion by fan operation.

UL60335-2-40 Ed.3 will be applied to North America. The application of UL60335-2-40 Ed.3 is scheduled for 2024 in North America and will be extended to other regions and products as corresponding laws and regulations are developed.
A2L refrigerants include R32, R1234yf, and its blends such as R454 etc.

Nissha FIS is developing a Metal Oxide Semiconductor (MOS) type sensor that complies with UL standards.

Excellent responsiveness: Detects leakage within 10 seconds
High detection accuracy: within ±15% of the concentration

Nissha FIS is in the process of developing a gas sensor module for A2L refrigerant detection that meets UL60335-2-40Ed.3. 
refrigerant sensor response
Responsiveness within 10 seconds

The UL standard specifies that a leak of a mildlly flammable refrigerant must be detected within 10 seconds.

Mildly flammable refrigerants have an increased potential to burn as their concentration increases.

Therefore Refrigerant Sensor need to detect the leak as soon as possible.

Nissha FIS has achieved a response time of less than 10 seconds as required by the standard.


refrigerant sensor accuracy
Detection accuracy of ±15% or less

UL standards require a concentration detection accuracy of within ±15%.

The test results on the right show that Nissha's semiconductor sensors can meet this requirement.

The test results on the right show the possibility that Nissha FIS semiconductor sensors can meet this required accuracy.



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Get the detail sensor specifications, responsivity and selectivity data.

Example of an air-conditioning system configuration including refrigerant sensor
1.PWM protocol version

2.RS485 (Modbus protocol) version

*No UART Signal Output

RS485 modbus


Sensor module mounting position
refrigerant sensor position
1.Suitable place to install the sensor

  ①Indoor Unit
  ②Detector at Low position in the room
  ③Exterior unit in a location isolated by a wall

 *Since the specific gravity of refrigerant is heavier than that of air,
  it is necessary to install it at a lower position than where there is a possibility of leakage.


Sensor Module

With Mounting Case

2.Sensor Hardware

The sensor module is available individually or with a case for protection and mounting. 


Features of the sensor that reduce the maintenance services

1.Long life of 15 years

It does not require calibration after installation and can be used for 15years without replacing the sensor.

2.Equipped with a filter for miscellaneous gases

The system is equipped with filters for spray gases used in daily life to reduce the risk of false alarms.


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