Earthing and lightning protection

Ring earth electrode calculator

Draw the building outline and place the down conductors. Get the ring length, joints and resistance.

CalculatorTechnical drawingMethod: R = 0.6·ρ/√A (DEHN, table 5.5.1) · BS 7430Built for an earthing systems manufacturer: case study

OUTLINE AND MATERIALS

Your ring earth plan

Choose an outline or draw one on the grid. You can change the dimensions with the mouse or in the fields.

Foundation slab

Slab reinforcement in contact with the soil acts as a foundation earth electrode. The calculator covers only the ring and vertical rods.

Ring earth distance from the building

Number of connection leads

pcs

Corners first, because lightning protection down conductors run there. Any extra leads go on the longest walls.

Extra length of each connection lead

In addition to the section between the ring earth and the wall. Include the vertical run and the route to the clamp.

Material reserve

Copper-bonded tape

Edit corners

Corner

X coordinate

Y coordinate

TOP VIEW / 1 m GRID

Building outline and ring earth

Drag a corner. Click a wall to change its length.

4 points

Wall dimensions

X marks horizontal walls in the drawing, Y vertical ones, S slanted ones. Type a length and press Enter: the wall end and the next corner move along it.

X1P1–P2m
Y1P2–P3m
X2P3–P4m
Y2P4–P1m

RING EARTH, THEN VERTICAL RODS

Earth resistance

Non-insulated slab

Soil resistivity

Ω·m

Don’t know the soil resistivity? Measure it with the Wenner method (step 2)

Number of vertical rods

pcs

On the ring earth, corners first, next to the leads.

Rod depthThe forged rod is made of 1.5 m sections, at most 4.5 m.

Required resistance

10 Ω: example from EN IEC 62305-3. The designer sets the requirement.

RING WITH RODS: RANGE

2.6–3.8 Ω

The ring earth alone meets 10.0 Ω

Ring earth3.78 ΩRods 4 × 3.0 m8.53 ΩArea inside the ring252.0 m² · r_e 9.0 m

Range: from an ideal parallel connection (2.62 Ω) to the ring alone (3.78 Ω). The rods interact with each other and with the ring, so the result lies above the lower bound.
Smallest rod spacing: 14.0 m. BS 7430 recommends at least twice the depth (6.0 m).
Slab reinforcement is not included in the resistance, so the result is conservative.

TAPE INCLUDING RESERVE

85.4 m

Quantities from geometry

Ring earth length64.0 mConnection leads13.7 mOutline area192.0 m²

Quantity plan: the ring earth is an offset of the outline sides with square corners. The joint count assumes full roll lengths in a closed loop and one connection per connection lead. Resistance is an estimate for uniform soil: ring R = 0.6·ρ/√A (consistent with DEHN, tab. 5.5.1), vertical rod per BS 7430. Cutting plan, additional joints, material selection and soil conditions must be checked in the design, and the resistance must be confirmed by measurement. The tool does not confirm compliance with standards.

RING EARTH CALCULATOR · PLAN AND RESISTANCE

Ring earth plan: non-insulated slab

Date

Resistance: ring with rods2.6–3.8 ΩRing earth: 3.78 Ω · rods 4 × 3.0 m: 8.53 ΩThe ring earth alone meets 10.0 Ω

Foundation slab: not insulated
Building outline: 192.0 m² · 56.0 m
Ring earth: 64.0 m · A = 252.0 m²
Distance from building: 1.0 m
Tape: 30 × 4 mm · 85.4 m
Connection leads: 4 pcs · +2.0 m
Soil resistivity ρ: 100.0 Ω·m
Vertical rods: 4 × 3.0 m · Ø 14.2 mm

Top view1 m grid · ring earth 1.0 m from the building wall · building wall dimensions

Building Ring earth Connection lead (L) Vertical rod

R_OT = 0,6 · ρ / √A (DEHN Lightning Protection Guide, tab. 5.5.1) · R_r = ρ / (2πL) · [ln(8L/d) − 1] (BS 7430:2011, cl. 9.5.3, d = 14.2 mm) · range from 1 / (1/R_OT + n/R_r) to R_OT, because the interaction of the ring and rods is not calculated.

Slab reinforcement is not included in the resistance. Preliminary calculation for uniform soil; the result must be checked in the design and by measurement after installation. Schematic drawing, dimensions come from the parameters.

Bill of materials

Quantities are a geometric suggestion; cutting plan, joints and fittings are agreed in the design. The designer enters prices from the distributor’s offer.

Item	Catalogue no.	Quantity	Price / unit [PLN]	Value [PLN]
Tape 30 × 4 mm		3 × 30 m = 90.0 m
Ring earth and connection lead joints		7 pcs
Forged earth rod 14.2 mm / 1.5 m		8 pcs
Rod to ring earth clamp		4 pcs
No complete price

NEXT STEP 2 OF 3

Soil resistivity by the Wenner method

Enter the meter readings, compare apparent resistivity and carry the result into the earthing calculation.

Go to step 2