During a ring final circuit test, what indicates the ring is intact?

• A. The loop resistance between the two end termination points is equal for both paths within tolerance
• B. The RCD trips immediately when tested
• C. The earth resistance is lower than 5 ohms
• D. The supply voltage remains constant

Answer: (A)

The test for a ring final circuit is about confirming that the loop around the ring is continuous. You check continuity by measuring the loop resistance between the end termination points and comparing the resistance of the two possible paths around the ring. If the ring is intact, both paths exist and have essentially the same resistance within the tester’s tolerance, meaning the circuit returns to its start without any breaks.

That’s why the correct indicator is that the loop resistance is equal for the two paths within tolerance—it shows both sides of the ring are connected and there’s no open conductor anywhere along the loop.

The other options aren’t about ring continuity: an RCD test relates to fault protection, earth resistance concerns the grounding path, and a constant supply voltage says nothing about the integrity of the ring loop.