Insulation and earth resistance check

Enter the measured insulation or earth resistance, and we show whether it is within the limit.

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What does the calculator check?

The calculator compares the measured value with the limit; the measurement itself is carried out by the electrician with a test instrument.

• Insulation resistance: for a normal circuit (up to 500 V) at least 1 MΩ at a test voltage of 500 V DC; for SELV and PELV (extra-low voltage) circuits at least 0.5 MΩ at 250 V DC.
• Earth resistance (TT system): with an RCD, the product of the earth resistance and the sensitivity of the RCD is at most 50 V, that is Ra ≤ 50 V / IΔn. With a 30 mA RCD this means at most 1666.7 Ω.

The calculator shows the limit, the test voltage (for insulation) and how much margin is left to the limit.

Limits of the calculation

The earth resistance check applies to the TT system and to the general touch voltage of 50 V; special locations (for example an environment with a lower touch voltage) and other systems require a separate assessment. The result is for guidance only: the acceptance measurement and the test report are prepared by the qualified professional.

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