Earth electrode resistance
How many electrodes do I drive to get below the required threshold?
Advanced conditions and parameters · Vertical electrodes (driven rod)
Result
✓Compliant — 2.844 Ω / 4 Ω
Art. 5.5.7.11 + Anexa 5.34 I7-2011
For the vertical electrode the simplified formula in Annex 5.34 is used, valid for lengths of 1…6 m — exactly the electrodes common in residential work. The detailed logarithmic relation could not be transcribed unambiguously from the extracted text of the standard, so we do not use it.
The actual soil resistivity varies with moisture and with the season. The value calculated here is a design estimate; acceptance is by measurement.
Calculation assumptions
The result holds under the conditions below. If your situation differs, change the values in the advanced section.
- the resistivity used is the value recommended for preliminary calculations; the actual soil is measured on site
- identical electrodes, installed at the same depth
The results are indicative and do not replace a design checked by a registered electrician. Every tool states its assumptions.