The IR test should be carried out between which terminals?

The insulation resistance (IR) test is designed to evaluate the integrity of the insulation of electrical conductors and ensure that they are not subject to leakage currents that could pose a danger or reduce the efficacy of the electrical system.

Carrying out the IR test between live conductors and earth is essential because it checks for any breakdown of insulation that might allow current to escape from the conductors and potentially energize the equipment casing or nearby conductive surfaces. This test is crucial for identifying any insulation failures that could lead to electric shock hazards or equipment damage.

Testing live conductors against earth effectively simulates real-world conditions where the insulation could fail and allows for the detection of issues well before they become hazardous. Therefore, this method helps in maintaining safety standards and ensuring the reliability of electrical installations.

The other options do not address the key purpose of the IR test as effectively. Testing between live conductors and neutral focuses on verifying the functionality of the circuit rather than insulation integrity. Additionally, testing between neutral and earth or between live conductors only assesses aspects of the circuit without effectively gauging insulation quality against a grounded reference, which could ultimately overlook potential fault conditions.