How to install an earthing system step by step (electrodes, strip, measurement)
An earthing system is the element that connects the electrical installation to earth in order to protect people from electrocution and equipment from overvoltages. In practice, it gives the fault current a safe path to the ground, so that the circuit breaker or the residual current device (RCD) trips quickly. In this guide we explain step by step how to install an earthing system: which electrodes and strip to use, how they are joined, how to reduce soil resistivity and how to verify everything through PRAM measurement.
What the earthing system is and why it matters
The earthing system (or earthing) is an assembly of buried metal electrodes, connected to each other and linked to the electrical installation through the protective conductor (PE) and the equipotential bonding bar. Its main role is to ensure:
- protection against electrocution - it disperses dangerous currents into the ground in case of a fault;
- correct operation of the protections - a good RCD without an efficient earthing system does not provide complete protection;
- protection against overvoltages - atmospheric discharges, network switching operations, lightning protection;
- the potential reference for sensitive devices and for photovoltaic equipment.
A properly installed and measured earthing system is also a requirement when connecting to the grid. The distribution operator, Retele Electrice Romania S.A. (formerly E-Distributie Muntenia / Enel, PPC group), may require an earthing verification certificate when energising the electrical connection (bransament).
Materials needed for the earthing system
All buried components must be made of corrosion-resistant materials, usually hot-dip galvanised steel (OL-Zn). Here are the basic elements.
| Element | Usual material | Indicative dimensions | Role |
|---|---|---|---|
| Vertical electrode | OL-Zn pipe/profile/angle bar or copper | Length 1.5-3 m | Disperses the current into the depth |
| Strip (horizontal electrode) | OL-Zn flat bar | 40x4 mm | Connects the electrodes to each other |
| Joints | Welding + clamps/clips | - | Electrical continuity |
| Separation piece | Test terminal/plate | - | Allows PRAM measurement |
| Connecting conductor | Copper or OL-Zn | as per design | Connects the earthing to the PE bar |
| Soil additives | Salt + bentonite | as required | Reduce resistivity |
The number of electrodes and the length of the strip are established according to the soil resistivity and the target resistance value. The drier, sandier or rockier the soil, the more electrodes or a more extensive earthing system are required.
How to install an earthing system step by step
Step 1 - Setting out and digging the trench
The route of the earthing system is established, usually a trench around the foundation or in a line/loop. The laying depth of the strip must be a minimum of 0.8 m, so that the earthing system remains in moist soil and below the frost depth. An earthing system placed too close to the surface has unstable resistance, high in summer and winter.
Step 2 - Driving in the vertical electrodes
The vertical electrodes (OL-Zn pipes or profiles of 1.5-3 m) are driven into the ground at the ends and along the route of the trench, at a distance from one another of at least the length of the electrode (usually 3 m between them). Correct spacing avoids “overlapping” of the influence zones and maintains low resistance. In hard soil, a pointed electrode-stake or drilling can be used.
Step 3 - Laying and welding the OL-Zn strip
The galvanised steel strip (typically 40x4 mm) is placed at the bottom of the trench and connected to each vertical electrode. The joints are made by welding, after which the welded area is given anti-corrosion protection (bitumen/paint), because welding destroys the local galvanising. Poor electrical continuity at the joints is one of the most frequent causes of a “bad” earthing system.
Step 4 - Reducing soil resistivity (salt and bentonite)
For lower dispersion resistance, a layer of salt mixed with bentonite (or commercial bentonite-based products) is added around the electrodes and the strip, and it is moistened. Bentonite retains moisture and maintains electrical contact over the long term. Caution: salt on its own accelerates corrosion, which is why it is used in combination and in moderation.
Step 5 - Backfilling the trench
The trench is covered with soil free of large stones or rubble, in compacted layers, for good contact between the strip and the soil. Filling with dry, draining material (clean gravel) should be avoided, as it increases resistance.
Step 6 - The separation piece and connecting to the bar
At the point where it emerges from the ground, a separation piece (test terminal) is mounted in an accessible box. This allows the earthing system to be disconnected for periodic measurement and verification. From here, the protective conductor runs to the equipotential bonding bar and to the electrical panel.
Step 7 - Measuring the dispersion resistance (PRAM)
After installation, the earthing system must be verified through PRAM measurement (Protection through Relays, Automation and Measurements) with a dedicated instrument. The dispersion resistance is determined and, if it is too high, electrodes or additives are added until the target value is reached. The result is recorded in a verification certificate signed by certified personnel.
What value the earthing system should have
The target value depends on the type of installation and the protections used. Below are usual indicative benchmarks (the exact values are established through the design and the applicable standards):
| Type of installation | Indicative target resistance |
|---|---|
| Domestic installation with RCD | usually <= 4 ohm |
| Common earthing at a transformer substation | <= 1 ohm |
| Earthing for lightning protection / LPS | <= 10 ohm (as per standard) |
| Sensitive equipment / photovoltaic | as per the manufacturer’s requirements |
Remember that an earthing system only “passes” if the measured value meets the requirement, and the measurement must be repeated periodically, because resistance increases over time through corrosion and drying of the soil.
Common mistakes when installing the earthing system
- Insufficient depth - a strip below 0.8 m leads to high and unstable values.
- Joints with bolts only, without welding - poor contact, rapid corrosion.
- Unsuitable material - non-galvanised steel or cross-sections that are too small and rust quickly.
- Lack of measurement - without a PRAM certificate you do not know whether the earthing system truly protects.
- Excess salt - it corrodes the electrodes and “eats away” the earthing system within a few years.
- Distances between electrodes that are too small - they do not reduce resistance proportionally.
Why you should call on an ANRE-certified company
The earthing system seems simple, but the final value depends on the soil, sizing, the quality of the welds and correct measurement. A company certified by ANRE for installation and design, such as SUN WATT SRL (bransam.ro), sizes the earthing system, installs it correctly and issues the PRAM certificate required at grid connection (racordare). We work in Bucharest, Ilfov and Giurgiu and can coordinate the earthing system with the rest of the works: electrical installations, earthing systems and PRAM measurements.
The earthing system is usually one piece of the puzzle of an electrical connection (bransament) or a grid connection for electricity. If you are installing panels, it is also essential for a safe prosumer / photovoltaic grid connection.
Indicative costs
At bransam.ro, an earthing system starts from 900 lei, and the PRAM measurement from 250 lei. The final price depends on the nature of the soil, the number of electrodes and the target value, and is confirmed after assessment. For a quote and to book an appointment, call 0733 097 440 or write to us through the contact page.
Conclusion
A correct earthing system means vertical electrodes driven in deep enough, connected with an OL-Zn strip through welding, soil treated for low resistivity and, most importantly, a PRAM measurement that confirms the target value. Without measurement, there is no guarantee that the installation protects you. Leave the installation and verification to an ANRE-certified team and you get a safe, compliant and documented earthing system.