A2L Sensors: Essential or Optional?
Commonly asked questions about A2L refrigerants and sensors
Does my chiller need A2L sensors?
Only if the chiller is certified to the UL 60335-2-40 safety standard. All other chillers do not require additional sensors and will safely operate in the same environment and manner as a chiller using an A1 refrigerant.
When does an A2L sensor trigger its alarm?
A2L sensors will not reach their trip point until the Lower Flammability Limit (LFL) of the refrigerant they are sensing has been reached. As shown in the chart below, a massive amount of R-454B needs to be released in a small space before the LFL is reached. For reference, 46 pounds is more than the entire refrigerant charge of a 30-ton chiller.
Can a spark ignite the refrigerant?
No. Even with the LFL requirement reached, A2L refrigerants must be exposed to an open flame or high-energy source to ignite as they have a high Minimum Ignition Energy.
How fast does the flame spread?
A2L refrigerants have a laminar flame speed of less than 10 centimeters per second (0.2 miles per hour), which is 10 times slower than the average walking speed of a 60-year-old person. So, even if the LFL was met and the A2L came in contact with an open flame, most people could calmly walk away much faster than the fire would spread.
R-454B Sensor Trip Point
| Average Size | Cubic Feet | LFL Requirement |
|---|---|---|
| Single story house | 15,300 | 337 lbs |
| Studio apartment | 5,400 | 119 lbs |
| College dorm room | 2,070 | 46 lbs |
| Walk-in closet | 540 | 12 lbs |
