MΩ
Insulation Resistance
Minimum insulation resistance values and test procedures from BS 7671 Table 61.
Minimum Values — Table 61
Minimum Insulation Resistance Values — Table 61
| Circuit Voltage | Test Voltage DC | Min IR (MΩ) |
|---|---|---|
| SELV / PELV | 250V | ≥0.5 |
| Up to 500V (inc 230V) | 500V | ≥1.0 |
| Above 500V | 1000V | ≥1.0 |
BS 7671: Table 61
Test Procedure
Preparation
1. Isolate supply at main switch 2. All fuses and MCBs in the ON position 3. Remove lamps and disconnect electronic equipment 4. Ensure pilot lights and capacitors are disconnected
Tests Required
Test between: 1. Line and Neutral (all combinations of live conductors) 2. Line and Earth 3. Neutral and Earth Each test must meet the minimum values from Table 61.
Note: A low reading may indicate damaged insulation, moisture ingress, or deteriorated wiring. Investigate any reading below 2MΩ even if above the minimum.
BS 7671: Reg 612.3
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