In the 80s Joule ratings were used to measure the ability of SPDs to protect the connected equipment, but UL1449 standardized on kA ratings instead of Joule ratings due to many SPD manufactures stating abnormally high Joule ratings for their SPDs that did not reflect the actual protection capacity of the SPD.

UL 1449 is the standard for testing the ability of surge protection devices and that test is measured in kA (thousand amp) rating.

Released for: Schneider Electric USA