Electrical reference chart
Grounding Resistance Chart
Use this worksheet after the calculator result to record soil resistivity, rod dimensions, spacing, estimated or measured ohms, target basis, and field verification.
Quick reference table
A grounding resistance chart is a calculator-led planning worksheet. It keeps estimated rod resistance, field-test resistance, target notes, and electrode spacing context together before owner, utility, or AHJ review.
Grounding resistance worksheet
| Field | Record from result | Follow-up |
|---|---|---|
| Electrode layout | Rod count, length, diameter, spacing | Confirm installed geometry |
| Soil basis | Measured or assumed resistivity | Document season and moisture conditions |
| Resistance value | Estimated or measured ohms | Compare with project target |
| Test method | Fall-of-potential or accepted method note | Attach instrument and setup notes |
| Review path | Owner, utility, or AHJ note | Close before using as final record |
Grounding test context worksheet
| Context item | Record on worksheet | Why it matters later |
|---|---|---|
| Probe setup | Probe spacing, direction, and obstructions | Fall-of-potential readings depend on setup geometry |
| Season and moisture | Date, weather, soil condition | Resistance can move with soil moisture and temperature |
| Nearby metal | Fences, buried piping, rebar, utilities | Parallel paths can distort field readings |
| Target basis | Owner, utility, project, or code-screening note | The acceptance target must be tied to its source |
How to use this chart
Separate estimate from test
Mark whether the ohm value came from the calculator model or from a field instrument.
Record electrode context
Write rod length, diameter, count, spacing, conductor path, and soil basis.
Close acceptance notes
Document the project target, owner or utility requirement, test setup, and AHJ follow-up.
Formula basis
Grounding record = electrode geometry + soil assumption + estimated or measured resistance + target basis + field-test method.
- Electrode geometry includes rod length, diameter, quantity, spacing, and connection path.
- Soil assumption is measured or estimated resistivity used for planning.
- Measured resistance is the field-test result in ohms.
- Target basis identifies whether the value is a project target, utility requirement, or code screening item.
Worked examples
Multi-rod grounding record
Record rod quantity, spacing, soil assumption, estimated array resistance, measured field result, test method, and project target before documenting acceptance.
Seasonal retest comparison
Keep spring and dry-season readings beside probe layout, instrument model, soil notes, and electrode geometry so the owner can compare trends.
Related calculators
Grounding Resistance Calculator
Estimate driven-rod grounding resistance, multi-rod screening, and supplemental-rod planning from soil resistivity and rod geometry.
Grounding Calculator
NEC Article 250 grounding and bonding conductor screen for main bonding jumpers, equipment grounding conductors, and grounding electrode conductors.
Electrical Testing Calculator
Screen insulation resistance, 62% fall-of-potential setup, contact resistance drift, and tan-delta trend movement without pretending to replace manufacturer or NETA acceptance criteria.
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Frequently asked questions
These answers explain how to use the chart without turning a quick reference into a final design decision.