The 140G-JTF3-D22 circuit breaker is a molded case circuit breaker from Allen-Bradley/Rockwell Automation. It belongs to the Allen-Bradley 140G series. Breakers in this family can be used in industrial environments with an ambient temperature below 0 degrees Celsius. However, use at temperatures below 0 degrees Celsius is based on the absence of freezing water in the operating environment. Therefore, while interfacing the 140G-JTF3-D22 circuit breaker with applications at a temperature below 0 degrees Celsius, the possibility of ice forming on or within the molded case circuit breaker and causing undesirable effects on the external and internal operating functionalities must be considered. Since the Allen-Bradley/Rockwell Automation 140G-JTF3-D22 circuit breaker uses a thermal/magnetic trip unit to provide protection, its operation is affected by the ambient temperature. The 140G-JTF3-D22 circuit breaker has a maximum operating temperature rating of 40 degrees Celsius. However, at a temperature below this rating, the breaker can carry more current than its normal current rating.

While it is unlikely the 140G-JTF3-D22 circuit breaker will exhibit any nuisance tripping at lower temperatures, closer protection coordination must be ensured to cater to the additional current. Note that at higher temperatures, the 140G-JTF3-D22 circuit breaker and other molded case circuit breakers are capable of carrying less current than their rated continuous current. Also, higher temperatures open the 140G-JTF3-D22 circuit breaker up for nuisance thermal tripping. The Allen-Bradley 140G-JTF3-D22 circuit breaker has an operating altitude of 2000 meters above sea level maximum. However, if the breaker is going to be operated at an altitude of over 2000 meters above sea level, it must be derated for interrupting rating and voltage. This is because the thinner air at higher altitudes reduces the cooling and dielectric characteristics of the breaker compared to the denser air at low altitudes.