In the context of inspection, what does 'R1 + R2' testing measure?

'R1 + R2' testing specifically measures the loop impedance of the final circuit conductors. In inspection and testing of electrical installations, particularly in the context of ensuring safety and compliance with regulations, this measurement is crucial for understanding how well the circuit can handle overloads and faults.

The 'R1' refers to the resistance of the phase conductor from the distribution board to the point of use, while 'R2' represents the resistance of the earth conductor. When combined, these resistances provide insight into the total impedance of the circuit loop. This is important for ensuring that protective devices, such as circuit breakers or fuses, will operate correctly in the event of a fault. A low loop impedance indicates that the system is likely to be safely earthed and will function as intended to protect against electrical faults. This testing helps verify the effectiveness of earthing arrangements and the integrity of connections in the installation.