When is it necessary to test Loop B in the fire detection system?

Testing Loop B in the fire detection system is essential when Loop A indicates a fault. This is because Loop B serves as a backup or redundancy to Loop A within the system. If Loop A shows a malfunction, it is crucial to evaluate Loop B to determine if the fault lies in Loop A or if there is a more significant issue with the system overall. This testing process ensures that the fire detection system remains operational and reliable.

Other scenarios, such as routine checks or maintenance, may involve examining these loops, but the immediate need to test Loop B arises specifically from an indication of fault in Loop A, ensuring a swift response to any potential fire detection issues.