Siemens GFCI circuit breakers are UL Listed and CSA Certified as Class A devices. Current imbalances of 4-6 milliamps or more between load conductors will cause the ground fault sensor to trip the circuit breaker.These circuit breakers offer the new Self Test & Lockout feature as required by UL 943. UL suggests GFCI devices be tested every 30 days after installation to ensure they are properly working. Testing GFCIs on a monthly basis is a good idea that is sometimes forgotten. Now, the new Self Test and Lockout feature enables the GFCI to automatically and continuously test itself to ensure that it is working properly. If it is detected that the device has been compromised, the device trips itself and locks out the homeowner from resetting the device, reducing the possibility of the homeowner incorrectly assuming that the device was tripped to prevent a ground fault. This will help guarantee the best protection is given to your home at all times.